Active-to-Sedentary Behavior Transitions, Fatigability, and Physical Functioning in Older Adults

Physical Behavior Profiles Among Older Adults and Their Associations With Physical Capacity and Life-Space Mobility

We identified data-driven multidimensional physical activity (PA) profiles using several novel accelerometer-derived metrics. Participants aged 75, 80, and 85 (n = 441) wore triaxial accelerometers for 3-7 days. PA profiles were formed with k-means cluster analysis based on PA minutes, intensity, fragmentation, sit-to-stand transitions, and gait bouts for men and women. Associations with physical capacity and life-space mobility were examined using age-adjusted general linear models. Three profiles emerged: "Exercisers" and "actives" accumulated relatively high PA minutes, with actives engaging in lighter intensity PA. "Inactives" had the highest activity fragmentation and lowest PA volume, intensity, and gait bouts. Inactives showed lower scores in physical capacity and life-space mobility compared with exercisers and actives. Exercisers and actives had similar physical capacity and life-space mobility, except female exercisers had higher walking speed in the 6-min walk test. Our findings demonstrate the importance of assessing PA as multidimensional behavior rather than focusing on a single metric.

Hearing Impairment and Physical Activity and Physical Functioning in Older Adults: Baseline Results From the ACHIEVE Trial

BACKGROUND

Hearing loss is associated with restricted physical activity (PA) and impaired physical functioning, yet the relationship between severity of hearing impairment (HI) and novel PA measures in older adults with untreated HI is not well understood.

METHODS

Analyses included 845 participants aged ≥70 years (mean = 76.6 years) with a better-hearing ear pure-tone average (PTA) ≥30 and <70 dB in the Aging and Cognitive Health Evaluation in Elders (ACHIEVE) study who wore an ActiGraph accelerometer for 7 days. Physical functioning measures included grip strength and the Short Physical Performance Battery (SPPB). Linear regression models estimated the association by HI level (moderate or greater [PTA ≥ 40 dB] vs mild [PTA < 40 dB]) and continuous hearing with total daily activity counts, active minutes/day, activity fragmentation, grip strength, and gait speed. Logistic regression models estimated odds ratios (ORs) and 95% confidence intervals (CIs) of poor performance on the SPPB (≤6) and its subtests (≤2). Mixed-effects models estimated differences by HI level in activity by time of day.

RESULTS

Participants with moderate or greater HI had poorer physical functioning, particularly balance (OR = 2.17, 95% CI = 1.29-3.67), versus those with mild impairment. There was no association of HI level with activity quantities or fragmentation. For diurnal patterns of activity, participants with moderate or greater HI had fewer activity counts in the afternoon (12:00 pm -05:59 pm).

CONCLUSIONS

Older adults with worse hearing had shifted diurnal patterns and poorer balance performance. Exercise programs should be tailored to older adults with different levels of HI to maintain PA and physical functioning, particularly balance control.

Differences in Daily Physical Activity by Alzheimer's Risk Markers Among Older Adults

BACKGROUND

Daily physical activity patterns differ by Alzheimer's disease (AD) status and might signal cognitive risk. It is critical to understand whether patterns are disrupted early in the AD pathological process. Yet, whether established AD risk markers (β-amyloid [Aβ] or apolipoprotein E-ε4 [APOE-ε4]) are associated with differences in objectively measured activity patterns among cognitively unimpaired older adults is unclear.

METHODS

Wrist accelerometry, brain Aβ (+/-), and APOE-ε4 genotype were collected in 106 (Aβ) and 472 (APOE-ε4) participants (mean age 76 [standard deviation{SD}: 8.5) or 75 [SD: 9.2] years, 60% or 58% women) in the Baltimore Longitudinal Study of Aging. Adjusted linear and function-on-scalar regression models examined whether Aβ or APOE-ε4 status was cross-sectionally associated with activity patterns (amount, variability, or fragmentation) overall and by time of day, respectively. Differences in activity patterns by combinations of Aβ and APOE-ε4 status were descriptively examined (n = 105).

RESULTS

There were no differences in any activity pattern by Aβ or APOE-ε4 status overall. Aβ+ was associated with lower total amount and lower within-day variability of physical activity overnight and early evening, and APOE-ε4 carriers had higher total amount of activity in the evening and lower within-day variability of activity in the morning. Diurnal curves of activity were blunted among those with Aβ+ regardless of APOE-ε4 status, but only when including older adults with mild cognitive impairment/dementia.

CONCLUSIONS

Aβ+ in cognitively unimpaired older adults might manifest as lower amount and variability of daily physical activity, particularly during overnight/evening hours. Future research is needed to examine changes in activity patterns in larger samples and by other AD biomarkers.

The Quantitative Impact of Visual Function on Accelerometer-measured Physical Activity in Older United States Adults: A Nationwide Cross-sectional Analysis

Purpose

To explore the impact of objective vision measures on novel metrics of objectively-measured physical activity (PA) in a nationally representative sample of United States (US) older adults.

Design

Cross-sectional analysis using data from the National Health and Aging Trends Study.

Participants

Adults had their distance and near visual acuity (VA) and contrast sensitivity (CS) tested. Any objective vision impairment (VI), defined as any VI in distance VA, near VA, or CS, was the primary exposure. Physical activity data were collected using the Actigraph CentrePoint Insight Watch worn for 7 days.

Methods

Multivariable regression models were used to investigate the association between vision and PA measures. All analyses accounted for the survey design and models were adjusted for age, sex, race, living arrangement, education, and comorbidities.

Main Outcome Measures

Physical activity metrics included (1) total daily activity (active minutes per day, number of active bouts, and mean length of active bouts), (2) activity fragmentation, and (3) time until 75% activity. An active bout was defined as ≥ 1 consecutive active minute. Activity fragmentation was defined as the probability of an active minute being followed by a sedentary minute, with higher values indicating more fragmented activity. Time until 75% activity was defined as the time taken to complete 75% of daily PA starting from their first active bout.

Results

Among 723 participants, sampled from 10 443 338 older adults in the US, 30% had any objective VI. Any objective VI was significantly associated with lower number of active minutes per day (7.8% fewer [95% confidence interval {CI}: -13.6% to -1.7%]), shorter active bouts (7.0% shorter [95% CI: -12.3% to -1.4%]), and greater activity fragmentation (2.5% [95% CI: 0.8% to 4.2%]), while no associations were found with number of active bouts. Time until 75% activity did not significantly differ between adults with any objective VI and those without (P = 0.34).

Conclusions

Older US adults with any objective VI displayed lower total daily activity, as well as more fragmented, shorter periods of PA, despite having a similar number of active bouts compared to their normally sighted counterparts. Implementing interventions that increase bout duration may help promote PA in adults with VI.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Physical Activity Fragmentation and Falls in Older Adults: Findings From the National Health and Aging Trends Study

BACKGROUND

Physical activity (PA) may be an important fall prevention strategy. Current PA guidelines emphasize total PA dose, but daily patterning of PA is underappreciated. With aging, PA bouts become less frequent and shorter in duration (ie, more fragmented). PA fragmentation may be an indicator of fall risk, but the relationship is not well understood. This study examined daily PA accumulation and patterns with fall risk in older adults.

METHODS

Participants (n = 685, 54.3% women, 61.5% aged 70-79 years) from the National Health and Aging Trends Study with wrist-worn accelerometry PA data from Round 11 (baseline) and sample person interviews with fall data from Round 12 (follow-up) were included. PA variables were categorized into tertiles and incident falls were defined as ≥1 self-reported fall in the year following the PA assessment between baseline and follow-up. A modified Poisson approach was used to estimate the relative risk of both PA accumulation and fragmentation with falls.

RESULTS

Overall, 40.0% reported an incident fall. After adjustment for sociodemographic and health characteristics, those in the highest tertile of total PA accumulation had lower fall risk (aRR = 0.74, 95% CI: 0.57, 0.95) and those in the highest tertile of PA fragmentation had increased fall risk (aRR = 1.33, 95% CI: 1.03, 1.73). Models were attenuated after adjustment for physical functioning.

CONCLUSIONS

PA fragmentation may identify fall risk in older adults. Longitudinal studies are needed to disentangle the temporal sequencing of the complex relationship between PA and physical functioning across the life course.

Relationship between skeletal mitochondrial function and digital markers of free-living physical activity in older adults

This study examined the association between in vivo skeletal mitochondrial function and digital free-living physical activity patterns-a measure that summarizes biological, phenotypic, functional, and environmental effects on mobility. Among 459 participants (mean age 68 years; 55% women) in the Baltimore Longitudinal Study of Aging, mitochondrial function was quantified as skeletal muscle oxidative capacity via post-exercise phosphocreatine recovery rate (τPCr) in the vastus lateralis muscle of the left thigh, using 31P magnetic resonance spectroscopy. Accelerometry was collected using a 7-day, 24-h wrist-worn protocol and summarized into activity amount, intensity, endurance, and accumulation patterning metrics. Linear regression, two-part linear and logistic (bout analyses), and linear mixed effects models (time-of-day analyses) were used to estimate associations between τPCr and each physical activity metric. Interactions by age, sex, and gait speed were tested. After covariate adjustment, higher τPCr (or poorer mitochondrial function) was associated with lower activity counts/day (β =  - 6593.7, SE = 2406.0; p = 0.006) and activity intensity (- 81.5 counts, SE = 12.9; p < 0.001). For activity intensity, the magnitude of association was greater for men and those with slower gait speed (interaction p < 0.02 for both). Conversely, τPCr was not associated with daily active minutes/day (p = 0.15), activity fragmentation (p = 0.13), or endurance at any bout length (p > 0.05 for all). Time-of-day analyses show participants with high τPCr were less active from 6:00 a.m. to 12:00 a.m. than those with low τPCr. Results indicate that poorer skeletal mitochondrial function is primarily associated with lower engagement in high intensity activities. Our findings help define the connection between laboratory-measured mitochondrial function and real-world physical activity behavior.

Cross-sectional associations between patterns and composition of upright and stepping events with physical function: insights from The Maastricht Study

INTRODUCTION

Age-related declines in physical functioning have significant implications for health in later life. Physical activity (PA) volume is associated with physical function, but the importance of the pattern in which PA is accumulated is unclear. This study investigates associations between accelerometer-determined daily PA patterns, including composition and temporal distribution (burstiness) of upright and stepping events, with physical function.

METHODS

Data was from participants who wore an activPAL3 accelerometer as part of The Maastricht Study. Exposures included a suite of metrics describing the composition and the temporal distribution (burstiness) of upright and sedentary behaviour. Physical function outcomes included the six-minute walk test (6MWT), timed chair-stand test (TCST), grip strength (GS), and SF-36 physical functioning sub-scale (SF-36pf). Multivariable linear regression models were used to assess associations, adjusting for covariates including overall PA volume (daily step count).

RESULTS

Participants(n = 6085) had 6 or 7 days of valid data. Upright and stepping event metrics were associated with physical function outcomes, even after adjusting PA volume. Higher sedentary burstiness was associated with better function (6MWT, TCST, and SF-36pf), as was duration and step volume of stepping events (6MWT, TCST, GS, and SF-36pf), step-weighted cadence (6MWT, TCST, and SF-36pf). Number of stepping events was associated with poorer function (6MWT, GS, and SF-36pf), as was upright event burstiness (SF-36pf). Associations varied according to sex.

CONCLUSION

Our study reveals that diverse patterns of physical activity accumulation exhibit distinct associations with various measures of physical function, irrespective of the overall volume. Subsequent investigations should employ longitudinal and experimental studies to examine how changing patterns of physical activity may affect physical function, and other health outcomes.

Cross-sectional associations between temporal patterns and composition of upright and stepping events with physical function in midlife: Insights from the 1970 British Cohort Study

INTRODUCTION

Age-related decline in physical functioning has significant implications for health in later life but declines begin earlier in midlife. Physical activity (PA) volume is associated with physical function, but the importance of the pattern in which PA is accumulated is unclear. This study investigates associations between patterns of PA accumulation, including the composition, variation, and temporal distribution of upright and stepping events, with physical function in midlife.

METHODS

Participants (n = 4378) from the 1970 British Cohort Study wore an activPAL3 accelerometer on the thigh for 7 consecutive days. Exposure measures included a suite of metrics describing the frequency, duration, and composition of upright events, as well as the duration and volume (total steps) of stepping events. In addition, patterns of accumulation of upright and sedentary events were examined including how fragmented/transient they were (upright-to-sedentary transition probability [USTP]) and their burstiness (the tendency for events to be clustered together followed by longer interevent times). Physical function outcomes included grip strength (GS), balance, and SF-36 physical functioning subscale (SF-36pf). Cross-sectional analyses included multivariable linear regression models to assess associations, adjusting for covariates including overall PA volume (mean daily step count).

RESULTS

Higher upright event burstiness was associated with higher GS, and higher USTP was associated with lower GS. Duration and step volume of stepping events were positively associated with SF-36pf in females. Step-weighted cadence was positively associated with SF-36pf and balance. Contradictory findings were also present (e.g., more transient stepping events were associated with better GS) particularly for GS in males. Inconsistencies between sexes were observed across some associations.

CONCLUSION

Our study reveals that diverse patterns of PA accumulation exhibit distinct associations with various measures of physical function in midlife, irrespective of the overall volume. Contradictory findings and inconsistency between sexes warrant further investigation. Patterns of PA accumulation, in addition to volume, should be considered in future PA research. Longitudinal studies are required to determine whether a given volume of activity accumulated in different patterns, impacts associations between PA and health outcomes.

Musculoskeletal Pain Characteristics and Objectively Measured Physical Activity in Older Adults

BACKGROUND

Pain is associated with reports of restricted physical activity (PA), yet the association between musculoskeletal pain characteristics and objectively measured PA quantities and patterns in late life is not well understood.

METHODS

A total of 553 adults (mean age 75.8 ± 8.4 years, 54.4% women) in the Baltimore Longitudinal Study of Aging (BLSA) completed a health interview and subsequent 7-day wrist-worn ActiGraph assessment in the free-living environment between 2015 and 2020. Pain characteristics, including pain presence in 6x sites (ie, shoulders, hands/wrists, low back, hip, knees, and feet), pain laterality in each site, and pain distribution were assessed. PA metrics were summarized into total daily activity counts (TAC), activity fragmentation, active minutes/day, and diurnal patterns of activity. Linear regression models and mixed-effects models examined the association between pain characteristics and PA outcomes, adjusted for demographics and comorbidities.

RESULTS

Unilateral knee pain was associated with 184 070 fewer TAC (p = .039) and 36.2 fewer active minutes/day (p = .032) compared to those without knee pain. Older adults with shoulder pain or hand/wrist pain had more active minutes compared to those without pain (p < .05 for all). For diurnal patterns of activity, participants with knee pain had fewer activity counts during the afternoon (12:00 pm to 5:59 pm). Analyses stratified by sex showed that these associations were only significant among women.

CONCLUSIONS

Our study highlights the importance of assessing pain laterality in addition to pain presence and suggests that pain interferes with multiple aspects of daily activity. Longitudinal studies are needed to assess the temporality of these findings.

Correlates of life course physical activity in participants of the Baltimore longitudinal study of aging

Physical activity is consistently associated with better health and longer life spans. However, the extent to which length and intensity of exercise across the life course impact health outcomes relative to current activity is undefined. Participants of the Baltimore Longitudinal Study of Aging were asked to categorize their level of physical activity in each decade of life from adolescence to the current decade. In linear mixed effects models, self-reported past levels of physical activity were significantly associated with activity assessed at study visits in the corresponding decade of life either by questionnaire or accelerometry. A pattern of life course physical activity (LCPA) derived by ranking participants on reported activity intensity across multiple decades was consistent with the trajectories of activity estimated from standard physical activity questionnaires assessed at prior study visits. In multivariable linear regression models LCPA was associated with clinical characteristics, measures of body composition and indicators of physical performance independent of current physical activity. After adjustment for minutes of high intensity exercise, LCPA remained significantly associated with peak VO2, fasting glucose, thigh muscle area and density, abdominal subcutaneous fat, usual gait speed, lower extremity performance, and multimorbidity (all p < 0.01) at the index visit. The observed associations suggest that an estimate of physical activity across decades provides complementary information to information on current activity and reemphasizes the importance of consistently engaging in physical activity over the life course.

A study on the relationship between recreational physical activity and audiovisual difficulty for older adults

Audiovisual difficulty are especially common in older adults. Audiovisual difficulty seriously affect the quality of life of older adults in their later years. It is a top priority to find out the related factors, and to intervene and prevent them. The purpose of this study was to explore the relationship between recreational physical activities and audiovisual difficulty in older adults. We hope that older adults can reduce the risk of hearing and visual difficulty through scientific physical activity. A total of 4,886 people were sampled from the National Health and Nutrition Examination Survey (NHANES) from 2013 to 2018. Recreational physical activity was assessed through the Global Physical Activity Questionnaire (GPAQ); Hearing and visual difficulty were assessed using the Disability Questionnaire (DLQ). Chi-square test was used for categorical variables and rank sum test was used for measurement variables. P < 0.05 was considered statistically significant (bilateral test). After univariate analysis, binary Logistic regression analysis was performed with recreational physical activity as the independent variable, statistically significant demographic variable as the covariate, and hearing and visual difficulty as the dependent variable, respectively. (1) After excluding all confounding variables, recreational physical activity was significantly associated with hearing difficulty (P < 0.001), odds ratio (OR) 0.657 (95% CI 0.5899-0.733); (2) Recreational physical activity was significantly associated with visual difficulty (P < 0.001), OR 0.731 (95% CI 0.630-0.849). (1) Recreational physical activity is the protective factor of hearing difficulty in older adults; (2) Recreational physical activity is a protective factor for visual difficulty in older adults.

Associations between performance-based and patient-reported physical functioning and real-world mobile sensor metrics in older cancer survivors: A pilot study

INTRODUCTION

Older cancer survivors are at increased risk for impaired physical functioning, but current assessments of function are difficult to implement in busy oncology clinics. Mobile devices measuring continuous activity and mobility in daily life may be useful for estimating physical functioning. The goal of this pilot study was to examine the associations between consumer wearable device (a wrist-worn activity tracker) and smartphone sensor data and commonly used clinical measures of physical function in cancer survivors aged 65 and older.

MATERIALS AND METHODS

Older adults within five years of completing primary treatment for any cancer completed standardized questionnaires and performance-based tests to measure physical functioning. Continuous passive data from smartphones and consumer wearable devices were collected for four weeks and linked to patient-reported and performance-based physical functioning as well as patient-reported falls or near falls at the end of the four-week monitoring period. To examine associations between sensor variables and physical functioning, we conducted bivariate Pearson correlations as well as multivariable linear regression analyses. To examine associations between sensor variables and falls, we conducted exploratory receiver operating characteristic curve and multivariable logistic regression analyses.

RESULTS

We enrolled 40 participants (mean age 73 years old, range 65-83; 98% White; 50% female). In bivariate analyses, consumer wearable device features reflecting greater amount and speed and lower fragmentation of walking in daily life were significantly related to better patient-reported function (r= 0.43-0.65) and performance-based physical function (r = 0.56-0.72), while smartphone features reflecting more geographic mobility were related to better performance-based physical function (r = 0.40-0.42) but not patient-reported function. After adjusting for age and comorbidities, only consumer wearable device features remained associated with performance-based physical functioning. In exploratory analyses, peak gait cadence was associated with fall risk even after covariate adjustment.

DISCUSSION

This study provides preliminary evidence that real-world data from consumer devices may be useful for estimating functional performance among older cancer survivors and potentially for remotely and longitudinally monitoring functioning in older patients during and after cancer treatment.

Unravelling upright events: a descriptive epidemiology of the behavioural composition and temporal distribution of upright events in participants from the 1970 British Cohort Study

BACKGROUND

Continued proliferation of accelerometers in physical activity research has opened new avenues for understanding activity behaviours beyond simple aggregate measures of frequency and duration. This study explores the standing and stepping composition, and the temporal distribution, of upright events, and investigates their associations with sociodemographic and health factors.

METHODS

Participants from the 1970 British Cohort Study wore activPAL3 accelerometers for seven days. Event-based analysis was used to extract a time series of upright, standing, and stepping events. Derived metrics included daily number of upright and stepping events, total upright and stepping time, the burstiness of upright events and burstiness of sedentary events (burstiness refers to the pattern of how physical activity and sedentary behaviour are distributed throughout a given time period), within-event stepping proportion, within-event step count, and stepping cadence. Generalized linear regression models, adjusted for total step count, were employed to explore associations between derived metrics and sociodemographic and health-related factors.

RESULTS

A total of 4527 participants, provided 30992 valid days (≥ 10 h of waking wear) and 1.64 million upright events. Upright event composition and temporal distribution varied across a range of sociodemographic and health-related factors. Females had more upright events than males (4.39 [3.41,5.38] n), spent more time upright, and exhibited burstier patterns of upright events (0.05 [0.04,0.05] Bn). Individuals with higher BMI had fewer upright events and a lower daily step count, but their temporal distribution of upright events was less bursty (overweight -0.02 [-0.02,-0.01] Bn; obese -0.03 [-0.04,-0.02] Bn), and upright events had a higher step count. People in active occupations were upright for longer, displayed burstier patterns of upright events (standing 0.04 [0.03,0.05] Bn; physical work 0.05 [0.04,0.05] Bn; heavy manual 0.06 [0.04,0.07] Bn), with more variable durations and shorter, slower paced stepping events compared with sedentary occupations.

CONCLUSIONS

This study has revealed novel phenotypes of standing and sitting that go beyond simple aggregate measures of total steps, step event duration or time between events. People with the same volume of stepping and frequency of gaps between upright events can accumulate their steps in very different ways. These differences and associations with population sub-groups, which persisted after adjustment for total stepping volume, may have important relations with functional and health outcomes. The findings lay the groundwork for future studies to investigate how different sitting and standing phenotypes can add to our understanding of the relationship between physical activity and health.

The Association Between Ankle-Brachial Index and Daily Patterns of Physical Activity: Results From the Hispanic Community Health Study/Study of Latinos

BACKGROUND

Peripheral artery disease (PAD) is associated with lower physical activity but less is known about its association with daily patterns of activity. We examined the cross-sectional association between ankle-brachial index (ABI) and objectively measured patterns of physical activity among Hispanic/Latino adults.

METHODS

We analyzed data from 7 688 participants (aged 45-74 years) in the Hispanic Community Health Study/Study of Latinos. ABI was categorized as low (≤0.90, indicating PAD), borderline low (0.91-0.99), normal (1.00-1.40), and high (>1.40, indicating incompressible ankle arteries). Daily physical activity metrics derived from accelerometer data included: log of total activity counts (LTAC), total log-transformed activity counts (TLAC), and active-to-sedentary transition probability (ASTP). Average differences between ABI categories in physical activity, overall and by 4-hour time-of-day intervals, were assessed using linear regression and mixed-effects models, respectively.

RESULTS

In Hispanic/Latino adults, 5.3% and 2.6% had low and high ABIs, respectively. After adjustment, having a low compared to a normal ABI was associated with lower volume (LTAC = -0.13, p < .01; TLAC = -74.4, p = .04) and more fragmented physical activity (ASTP = 1.22%, p < .01). Having a low ABI was linked with more fragmented physical activity after 12 pm (p < .01). Having a high ABI was associated with lower volumes of activity (TLAC = -132.0, p = .03).

CONCLUSIONS

Having a low or high ABI is associated with lower and more fragmented physical activity in Hispanic/Latino adults. In adults with low ABI, physical activity is more fragmented in the afternoon to evening. Longitudinal research is warranted to expand these findings to guide targeted interventions for PAD or incompressible ankle arteries.

Association between accelerometry measured patterns of sedentary behaviors and functional status in older adults

BACKGROUND

Older adults are highly sedentary, and too much sedentary behavior (SB) is associated with negative health effects, but little is known about SB patterns and their associations with functional status.

AIMS

To examine the association between objectively measured sedentary behavior time (SBT) and sedentary behavior fragmentation (SBF) and functional status in older adults using the National Health Aging Trends Study (NHATS) dataset, a nationally representative sample from 2021.

METHODS

Data from NHATS were analyzed using weighted linear regressions to examine the association between objective measures of SBT (mean hours spent in SB/day during waking hours) and SBF, and six functional variables (difficulties with activities of daily living [ADL], short physical performance battery, hand grip strength, immediate word recall, delayed word recall, and mental health), accounting for sociodemographic, body mass index, and the number of chronic conditions.

RESULTS

A total of 738 individuals from the NHATS were included. Higher SBT was associated with greater difficulties with ADL, poorer short physical performance battery and hand grip strength, lower scores in both immediate and delayed word recall, and poorer mental health. Higher SBF was associated with fewer difficulties with ADL, better short physical performance battery and hand grip strength, a higher score in immediate word recall, and better mental health.

DISCUSSIONAND CONCLUSIONS

Greater fragmentation of SB was associated with better function, and increasing SBF may be a useful strategy for mitigating the effects of SB in older adults, but prospective research is needed to support this approach.

Variability in exercise is linked to improved age-related dysfunctions: A potential role for the constrained-disorder principle-based second-generation artificial intelligence system

Objective: Regular physical activity (PA) promotes mental and physical health. Nevertheless, inactivity is a worldwide pandemic, and methods to augment exercise benefits are required. The constrained disorder principle (CDP) characterizes biological systems based on their inherent variability. We aimed to investigate the association between intra-individual variability in PA and disability among non-athlete adults. Methods: In this retrospective analysis of the longitudinal SHARE survey, we included non-disabled adults aged >50 with at least six visits over 14 years. Self-reported PA frequency was documented bi- to triennially. Low PA intensity was defined as vigorous PA frequency less than once a week. Stable PA was described as an unchanged PA intensity in all consecutive middle observations. The primary outcome was defined as a physical limitation in everyday activities at the end of the survey. Secondary outcomes were cognitive functions, including short-term memory, long-term memory, and verbal fluency. Results: The study included 2,049 non-disabled adults with a mean age of 53 and 49.1% women. In the initially high PA intensity group, variability in PA was associated with increased physical disability prevalence (23.3% vs. 33.2%, stable vs. unstable PA ; P<0.01; adjusted P<0.01). In the initially low PA intensity group, variability was associated with a reduced physical disability (45.6% vs. 33.3%, stable vs. unstable PA ; P=0.02; adjusted P=0.03). There were no statistically significant differences in cognitive parameters between the groups. Among individuals with the same low PA intensity at the beginning and end of follow-up, variability was associated with reduced physical disability (56.9% vs. 36.5%, stable vs. unstable PA ; P=0.02; adjusted P=0.04) and improved short-term memory (score change: -0.28 vs. +0.29, stable vs. unstable PA ; P=0.05). Conclusion: Incorporating variability into PA regimens of inactive adults may enhance their physical and cognitive benefits.

Can Gait Characteristics Be Represented by Physical Activity Measured with Wrist-Worn Accelerometers?

Wearable accelerometers allow for continuous monitoring of function and behaviors in the participant's naturalistic environment. Devices are typically worn in different body locations depending on the concept of interest and endpoint under investigation. The lumbar and wrist are commonly used locations: devices placed at the lumbar region enable the derivation of spatio-temporal characteristics of gait, while wrist-worn devices provide measurements of overall physical activity (PA). Deploying multiple devices in clinical trial settings leads to higher patient burden negatively impacting compliance and data quality and increases the operational complexity of the trial. In this work, we evaluated the joint information shared by features derived from the lumbar and wrist devices to assess whether gait characteristics can be adequately represented by PA measured with wrist-worn devices. Data collected at the Pfizer Innovation Research (PfIRe) Lab were used as a real data example, which had around 7 days of continuous at-home data from wrist- and lumbar-worn devices (GENEActiv) obtained from a group of healthy participants. The relationship between wrist- and lumbar-derived features was estimated using multiple statistical methods, including penalized regression, principal component regression, partial least square regression, and joint and individual variation explained (JIVE). By considering multilevel models, both between- and within-subject effects were taken into account. This work demonstrated that selected gait features, which are typically measured with lumbar-worn devices, can be represented by PA features measured with wrist-worn devices, which provides preliminary evidence to reduce the number of devices needed in clinical trials and to increase patients' comfort. Moreover, the statistical methods used in this work provided an analytic framework to compare repeated measures collected from multiple data modalities.

Associations between patterns of physical activity, pain intensity, and interference among older adults with chronic pain: a secondary analysis of two randomized controlled trials

Background: Clinical management of chronic pain often includes recommendations to engage in physical activity (PA), though there are little data on the interplay between pain symptoms and key aspects of PA participation (e.g., intensity and bout duration) among older adults. Herein we investigate the longitudinal relationships between changes in PA behavior and changes in pain intensity and interference among low-active older adults with obesity and chronic pain. Methods: Participants (N = 41) were enrolled in two randomized pilot trials wherein they were assigned to an intervention focused on participation in frequent PA across the day, or to a low-contact control. Participants completed the 3-item PROMIS pain intensity scale and 8-item PROMIS pain interference scale before and after the interventions. Participants also wore an ActivPAL accelerometer for 7 days before and during the final week of the interventions. Results: A series of linear regression analyses demonstrated that increased time spent stepping at a high-light intensity in very short bouts was associated with increased pain intensity scores. By contrast, increased time spent stepping at a high-light intensity in bouts of 5-20 min was associated with reductions in pain intensity and interference scores. Increased time spent stepping at a moderate intensity overall was associated with reduced pain intensity scores, and time spent stepping at a moderate intensity for 10-20 min associated with reduced pain interference. Conclusion: These findings suggest older adults with chronic pain may benefit by moving at high-light or moderate intensities in brief bouts of at least 5 min in duration.

The association of vitamin D supplementation and serum vitamin D levels with physical activity in older adults: Results from a randomized trial

BACKGROUND

To assess whether vitamin D3 supplementation attenuates the decline in daily physical activity in low-functioning adults at risk for falls.

METHODS

Secondary data analyses of STURDY (Study to Understand Fall Reduction and Vitamin D in You), a response-adaptive randomized clinical trial. Participants included 571 adults aged 70 years and older with baseline serum 25(OH)D levels of 10-29 ng/mL and elevated fall risk, who wore a wrist accelerometer at baseline and at least one follow-up visit and were randomized to receive: 200 IU/day (control), 1000, 2000, or 4000 IU/day of vitamin D3 . Objective physical activity quantities and patterns (total daily activity counts, active minutes/day, and activity fragmentation) were measured for 7-days, 24-h/day, in the free-living environment using the Actigraph GT9x over up to 24-months of follow-up.

RESULTS

In adjusted models, physical activity quantities declined (p < 0.001) and became more fragmented, or "broken up", (p = 0.017) over time. Supplementation with vitamin D3 did not attenuate this decline. Changes in physical activity were more rapid among those with baseline serum 25(OH)D <20 ng/mL compared to those with baseline 25(OH)D levels of 20-29 ng/mL (time*baseline 25(OH)D, p < 0.05).

CONCLUSION

In low-functioning older adults with serum 25(OH)D levels 10-29 ng/mL, vitamin D3 supplementation of 1000 IU/day or higher did not attenuate declines in physical activity compared with 200 IU/day. Those with baseline 25(OH)D <20 ng/mL showed accelerated declines in physical activity. Alternative interventions to supplementation are needed to curb declines in physical activity in older adults with low serum 25(OH)D.

Bouts of rest and physical activity in C57BL/6J mice

The objective was to exploit the raw data output from a scalable home cage (type IIL IVC) monitoring (HCM) system (DVC®), to characterize pattern of undisrupted rest and physical activity (PA) of C57BL/6J mice. The system's tracking algorithm show that mice in isolation spend 67% of the time in bouts of long rest (≥40s). Sixteen percent is physical activity (PA), split between local movements (6%) and locomotion (10%). Decomposition revealed that a day contains ˜7100 discrete bouts of short and long rest, local and locomotor movements. Mice travel ˜330m per day, mainly during the dark hours, while travelling speed is similar through the light-dark cycle. Locomotor bouts are usually <0.2m and <1% are >1m. Tracking revealed also fits of abnormal behaviour. The starting positions of the bouts showed no preference for the rear over the front of the cage floor, while there was a strong bias for the peripheral (75%) over the central floor area. The composition of bouts has a characteristic circadian pattern, however, intrusive husbandry routines increased bout fragmentation by ˜40%. Extracting electrode activations density (EAD) from the raw data yielded results close to those obtained with the tracking algorithm, with 81% of time in rest (<1 EAD s-1) and 19% in PA. Periods ≥40 s of file when no movement occurs and there is no EAD may correspond to periods of sleep (˜59% of file time). We confirm that EAD correlates closely with movement distance (rs>0.95) and the data agreed in ˜97% of the file time. Thus, albeit EAD being less informative it may serve as a proxy for PA and rest, enabling monitoring group housed mice. The data show that increasing density from one female to two males, and further to three male or female mice had the same effect size on EAD (˜2). In contrast, the EAD deviated significantly from this stepwise increase with 4 mice per cage, suggesting a crowdedness stress inducing sex specific adaptations. We conclude that informative metrics on rest and PA can be automatically extracted from the raw data flow in near-real time (< 1 hrs). As discussed, these metrics relay useful longitudinal information to those that use or care for the animals.

Physical Activity Over the Lifecourse and Cardiovascular Disease

Despite improvements in cardiovascular care in recent decades, cardiovascular disease (CVD) remains a leading cause of death worldwide. At its core, CVD is a largely preventable disease with diligent risk factor management and early detection. As highlighted in the American Heart Association's Life's Essential 8, physical activity plays a central role in CVD prevention at an individual and population level. Despite pervasive knowledge of the numerous cardiovascular and noncardiovascular health benefits of physical activity, physical activity has steadily decreased over time and unfavorable changes in physical activity occur throughout people's lives. Here, we use a lifecourse framework to examine the evidence reporting on the association of physical activity with CVD. From in utero to older adults, we review and discuss the evidence detailing how physical activity may prevent incident CVD and mitigate CVD-related morbidity and death across all life stages.

The association between daily sedentary and active bout frequency with mortality risk in older men using accelerometry

BACKGROUND

Time awake with advancing age is increasingly spent sedentary and has several negative health consequences. We examined associations between the frequency of daily sedentary and active bouts with all-cause mortality.

METHODS

Data are from 2816 men in the Osteoporotic Fractures in Men (MrOS) Study (mean age ± SD: 79.1 ± 5.2 years) with free-living activity monitor (SenseWear® Pro3 Armband) data (5.1 ± 0.3 days worn >90%) at the Year 7 visit (2007-2009). Sedentary bout frequency was defined as the number of sedentary bouts per day lasting 5+ min to activity of any intensity. Active bout frequency was defined as the number of active bouts per day lasting 5+ min to sedentary behavior. Sleep time was excluded from the analysis. Deaths were centrally adjudicated using death certificates. Cox proportional hazard models were used to separately examine associations between quartiles of sedentary (Q1 referent, <13.6 bouts/day) or active (Q1 referent, <5 bouts/day) bout frequency with mortality.

RESULTS

After 9.3 ± 3.8 years of follow-up, 1487 (52.8%) men died. Men averaged 16.8 ± 5.1 and 8.2 ± 4.2 sedentary and active bouts/day, respectively. After full covariate adjustment, each quartile reflecting more frequent sedentary bouts (Q4 vs. Q1 HR: 0.69, 95%CI: 0.58, 0.81, p-trend <0.001) was associated with lower mortality risk. Likewise, each quartile reflecting more frequent active bouts (Q4 vs. Q1 HR: 0.58, 95%CI: 0.49, 0.70, p-trend <0.001) was associated with lower mortality risk. Results for the sedentary bouts model remained significant after adjusting for total minutes per day in sedentary behavior (Q4 vs. Q1 HR: 0.63, 95%CI: 0.61, 0.86, p-trend = 0.001). The association between active bout frequency with mortality was attenuated after adjusting for total minutes per day active.

CONCLUSIONS

Regardless of total time spent sedentary, reducing duration of sedentary bouts with more frequent and shorter bouts may be a simple and feasible method to delay mortality risk among community-dwelling older men.

Purpose in life and accelerometer-measured physical activity among older adults

OBJECTIVE

Purpose in life is associated with engagement in physical activity and better cognitive health. This study examines the association between purpose in life and patterns of physical activity measured with an accelerometer and whether these patterns mediate the association between purpose and episodic memory among older adults.

METHODS AND MEASURES

This research is a secondary analysis of data from the accelerometry sub-study of the National Health and Aging Trends Study. Participants (N = 747; mean age = 79.20) reported on their purpose, wore an accelerometer for eight days, and completed an episodic memory task.

RESULTS

Purpose in life was associated with healthier patterns of physical activity, including higher total activity counts (β = .10, p = .002), more active bouts per day (β = .11, p = .003), less activity fragmentation (β = -.17, p < .001) and more sedentary fragmentation (β = .11, p = .002). These associations were generally similar across age, sex, race and education. Higher total activity counts and less activity fragmentation were associated with better episodic memory and accounted for part of the association between purpose and episodic memory.

CONCLUSION

Purpose in life is associated with healthier patterns of physical activity measured through accelerometry among older adults and such patterns may be one factor in the pathway from purpose to healthier episodic memory.

Patterns of Daily Physical Movement, Chronic Inflammation, and Frailty Incidence

INTRODUCTION

Low physical activity is a criterion of phenotypic frailty defined as an increased state of vulnerability to adverse health outcomes. Whether disengagement from daily all-purpose physical activity is prospectively associated with frailty and possibly modified by chronic inflammation-a pathway often underlying frailty-remains unexplored.

METHODS

Using the Study to Understand Fall Reduction and Vitamin D in You data from 477 robust/prefrail adults (mean age = 76 ± 5 yr; 42% women), we examined whether accelerometer patterns (activity counts per day, active minutes per day, and activity fragmentation [broken accumulation]) were associated with incident frailty using Cox proportional hazard regression. Baseline interactions between each accelerometer metric and markers of inflammation that include interleukin-6, C-reactive protein, and tumor necrosis factor-alpha receptor 1 were also examined.

RESULTS

Over an average of 1.3 yr, 42 participants (9%) developed frailty. In Cox regression models adjusted for demographics, medical conditions, and device wear days, every 30 min·d -1 higher baseline active time, 100,000 more activity counts per day, and 1% lower activity fragmentation was associated with a 16% ( P = 0.003), 13% ( P = 0.001), and 8% ( P < 0.001) lower risk of frailty, respectively. No interactions between accelerometer metrics and baseline interleukin-6, C-reactive protein, or tumor necrosis factor-alpha receptor 1 were detected (interaction P > 0.06 for all).

CONCLUSIONS

Among older adults who are either robust or prefrail, constricted patterns of daily physical activity (i.e., lower total activity minutes and counts, and higher activity fragmentation) were prospectively associated with higher risk of frailty but not modified by frailty-related chronic inflammation. Additional studies, particularly trials, are needed to understand if this association is causal.

Modular hip exoskeleton improves walking function and reduces sedentary time in community-dwelling older adults

BACKGROUND

Despite the benefits of physical activity for healthy physical and cognitive aging, 35% of adults over the age of 75 in the United States are inactive. Robotic exoskeleton-based exercise studies have shown benefits in improving walking function, but most are conducted in clinical settings with a neurologically impaired population. Emerging technology is starting to enable easy-to-use, lightweight, wearable robots, but their impact in the otherwise healthy older adult population remains mostly unknown. For the first time, this study investigates the feasibility and efficacy of using a lightweight, modular hip exoskeleton for in-community gait training in the older adult population to improve walking function.

METHODS

Twelve adults over the age of 65 were enrolled in a gait training intervention involving twelve 30-min sessions using the Gait Enhancing and Motivating System for Hip in their own senior living community.

RESULTS

Performance-based outcome measures suggest clinically significant improvements in balance, gait speed, and endurance following the exoskeleton training, and the device was safe and well tolerated. Gait speed below 1.0 m/s is an indicator of fall risk, and two out of the four participants below this threshold increased their self-selected gait speed over 1.0 m/s after intervention. Time spent in sedentary behavior also decreased significantly.

CONCLUSIONS

This intervention resulted in greater improvements in speed and endurance than traditional exercise programs, in significantly less time. Together, our results demonstrated that exoskeleton-based gait training is an effective intervention and novel approach to encouraging older adults to exercise and reduce sedentary time, while improving walking function. Future work will focus on whether the device can be used independently long-term by older adults as an everyday exercise and community-use personal mobility device. Trial registration This study was retrospectively registered with ClinicalTrials.gov (ID: NCT05197127).

Changes in Objectively Measured Physical Activity Are Associated With Perceived Physical and Mental Fatigability in Older Men

BACKGROUND

Lower physical activity (PA) is associated with greater perceived fatigability, a person-centered outcome. The association between change in PA and fatigability with advanced age has yet to be established.

METHODS

Community-dwelling older men (N = 1 113, age = 84.1 ± 3.9 years at Year 14) had free-living PA assessed using SenseWear Armband prospectively at Year 7 (2007-2009) and Year 14 (2014-2016) of Osteoporotic Fractures in Men Study, a longitudinal cohort established in 2000 (baseline). We categorized percent changes in PA into groups (large decline → large increase) for 4 metrics: step count, light intensity PA (LIPA, metabolic equivalents [METs] >1.5 to <3.0), moderate-to-vigorous PA (MVPA, METs ≥ 3.0), and sedentary behavior (SB, METs ≤ 1.5, excluding sleep). Perceived physical and mental fatigability were measured (Year 14) with the Pittsburgh Fatigability Scale (PFS, higher score = greater fatigability; range = 0-50). Associations between each metric of percent changes in PA and fatigability were examined using linear regression, adjusted for demographics, change in health conditions, and Year 7 step count or total PA (METs > 1.5).

RESULTS

Men declined 2 336 ± 2 546 (34%) steps/d, 24 ± 31 (25%) LIPA min/d, 33 ± 58 (19%) MVPA min/d, and increased 40 ± 107 (6%) SB min/d over 7.2 ± 0.7 years. Compared to large decline (% change less than -50%), those that maintained or increased step count had 3-8 points lower PFS Physical scores; those who maintained or increased LIPA and MVPA had 2-3 and 2-4 points lower PFS Physical scores, respectively (all p ≤ .01). Associations were similar, but smaller, for PFS Mental scores.

CONCLUSION

Older men who maintained or increased PA had lower fatigability, independent of initial PA. Our findings inform the types and doses of PA that should be targeted to reduce fatigability in older adults.

Prospective Associations Between Physical Activity and Perceived Fatigability in Older Men: Differences by Activity Type and Baseline Marital Status

BACKGROUND

Lower physical activity has been cross-sectionally associated with greater perceived fatigability, defined as self-reported fatigue anchored to activity intensity and duration. The temporality of this relationship, and whether it differs by activity type or marital status, remains unclear.

METHODS

In the Osteoporotic Fractures in Men Study (N = 1 759), self-reported total, exercise, and household activity were assessed using the Physical Activity Scale for the Elderly across 7 visits (2000-2016). The Pittsburgh Fatigability Scale (range: 0-50; higher scores = greater fatigability) measured physical (mean = 16.6 ± 9.7) and mental (mean = 7.8 ± 8.3) fatigability at Year 14. Least absolute deviation and linear regression were used to examine associations between baseline and change in activity over 14 years with subsequent fatigability. Models were adjusted for demographic, health, and lifestyle factors.

RESULTS

After adjustment, lower baseline (β= -0.08, 95% confidence interval [CI]: -0.12, -0.04) and greater annual declines in total activity (β = -0.09, 95% CI: -0.14, -0.05) were prospectively associated with higher Pittsburgh Fatigability Scale (PFS) Physical scores. Associations were similar for mental fatigability (both p < .05). Lower baseline leisure exercise, but not baseline household activity, predicted higher PFS Physical scores (β = -0.10 vs -0.001). In contrast, greater declines in household activity, but not declines in exercise, were associated with higher PFS Physical scores (β = -0.09 vs -0.03). Lower baseline household activity predicted higher PFS Mental scores only for unmarried men (β = -0.15, 95% CI: -0.29, -0.01, interaction p = .019).

CONCLUSIONS

Baseline total activity and leisure exercise, and declines in total and household activity, were associated with higher subsequent perceived fatigability in older men. Marital status may mitigate the contribution of household activity to subsequent fatigability.

Historical development of accelerometry measures and methods for physical activity and sedentary behavior research worldwide: A scoping review of observational studies of adults

This scoping review identified observational studies of adults that utilized accelerometry to assess physical activity and sedentary behavior. Key elements on accelerometry data collection were abstracted to describe current practices and completeness of reporting. We searched three databases (PubMed, Web of Science, and SPORTDiscus) on June 1, 2021 for articles published up to that date. We included studies of non-institutionalized adults with an analytic sample size of at least 500. The search returned 5686 unique records. After reviewing 1027 full-text publications, we identified and abstracted accelerometry characteristics on 155 unique observational studies (154 cross-sectional/cohort studies and 1 case control study). The countries with the highest number of studies included the United States, the United Kingdom, and Japan. Fewer studies were identified from the continent of Africa. Five of these studies were distributed donor studies, where participants connected their devices to an application and voluntarily shared data with researchers. Data collection occurred between 1999 to 2019. Most studies used one accelerometer (94.2%), but 8 studies (5.2%) used 2 accelerometers and 1 study (0.6%) used 4 accelerometers. Accelerometers were more commonly worn on the hip (48.4%) as compared to the wrist (22.3%), thigh (5.4%), other locations (14.9%), or not reported (9.0%). Overall, 12.7% of the accelerometers collected raw accelerations and 44.6% were worn for 24 hours/day throughout the collection period. The review identified 155 observational studies of adults that collected accelerometry, utilizing a wide range of accelerometer data processing methods. Researchers inconsistently reported key aspects of the process from collection to analysis, which needs addressing to support accurate comparisons across studies.

Association of non-chronic low back pain with physical function, endurance, fatigability, and quality of life in middle- and older-aged adults: Findings from Baltimore Longitudinal Study of Aging

Low back pain (LBP) is an important condition associated with high healthcare burden. However, the relationship of this condition with physical function (PF) and health-related quality of life (HRQoL) remains unclear. This is a cross-sectional study that aims to investigate the association between presence and intensity of non-chronic LBP with PF and HRQoL in middle-and older-aged adults. Participants answered questions about presence and intensity of LBP in the previous year, self-reported their PF and HRQoL (SF-12), and underwent objective measures of PF ([ExSPPB] including usual gait speed, narrow walk, chair stands, and standing balance), endurance performance ([EP] long-distance corridor walk) and fatigability. Generalized linear models and logistic regression models were performed. A total of 1500 participants (52.5% women, 70.3% white) aged 69.0 (SD 13.1) years were included. Of those, 642 (42.8%) reported LBP and the mean pain intensity was 4.1 (SD 2.2). After adjustments for potential confounders, presence of LBP was associated with lower self-reported PF (OR 1.73, 95% CI 1.27 to 2.37), lower physical component of HRQoL (β -0.03, 95% CI -0.04 to -0.02) and poorer chair stand performance (β -0.05, 95% CI -0.09 to -0.008). Higher intensity of LBP was associated with lower physical component of HRQoL (β -0.01, 95% CI -0.02 to -0.007), poorer ExSPPB performance (β -0.01, 95% CI -0.02 to -0.004), slower usual gait speed (β -0.01, 95% CI -0.02 to -0.004), lower total standing balance time (β -0.01, 95% CI -0.02 to -0.001) and higher fatigability (OR 1.13, 95% CI 1.01 to 1.25). The presence of non-chronic LBP was more consistently associated with lower self-reported PF, while higher intensity non-chronic LBP was associated with poorer objectively measured PF and fatigability. Collectively, this evidence suggests that although presence of pain may affect perception of function, greater pain intensity appears more strongly associated with unfavorable functional performance in mid-to-late life.

Cardiorespiratory Fitness as a Moderator of Sleep-Related Associations with Hippocampal Volume and Cognition

The objective of this study was to understand the associations of sleep and cardiorespiratory fitness with hippocampal volume and global cognition among older adults (n = 30, age = 65.8 years, female = 73.3%). Wrist actigraphy provided objective measures of nighttime sleep including sleep duration, average wake bout length (WBL; sleep disturbance), and wake-to-sleep transition probability (WTSP; sleep consolidation). Cardiorespiratory fitness was quantified via cycle exercise using a modified heart rate recovery approach. Magnetic resonance imaging was used to determine hippocampal volume and the Mini-Mental State Examination was used to assess global cognition. Fitness moderated associations of sleep with hippocampal volume and cognitive performance, whereby the association of WBL-an index of poor sleep-with hippocampal atrophy was stronger among less-fit individuals, and the association of sleep duration with cognitive performance was stronger among more-fit individuals. Across the fitness levels, a longer WBL was associated with lower cognitive performance, and a higher WTSP-an index of more consolidated sleep-was associated with greater hippocampal volume. Sleep and fitness were unrelated to the volume of an amygdala control region, suggesting a degree of neuroanatomical specificity. In conclusion, higher cardiorespiratory fitness may attenuate sleep disturbance-related hippocampal atrophy and magnify the cognitive benefits of good sleep. Prospective studies are needed to confirm these findings.

Patterns of objectively measured physical activity differ between men living with and without HIV

OBJECTIVE

To use accelerometers to quantify differences in physical activity (PA) by HIV serostatus and HIV viral load (VL) in the Multicenter AIDS Cohort Study (MACS).

METHODS

MACS participants living with (PLWH, n = 631) and without (PWOH, n = 578) HIV wore an ambulatory electrocardiogram monitor containing an accelerometer for 1-14 days. PA was summarized as cumulative mean absolute deviation (MAD) during the 10 most active consecutive hours (M10), cumulative MAD during the six least active consecutive hours (L6), and daily time recumbent (DTR). PA summaries were compared by HIV serostatus and by detectability of VL (>20 vs. ≤20 copies/ml) using linear mixed models adjusted for sociodemographics, weight, height, substance use, physical function, and clinical factors.

RESULTS

In sociodemographic-adjusted models, PLWH with a detectable VL had higher L6 (β = 0.58 mg, P = 0.027) and spent more time recumbent (β = 53 min/day, P = 0.003) than PWOH. PLWH had lower M10 than PWOH (undetectable VL β = -1.62 mg, P = 0.027; detectable VL β = -1.93 mg, P = 0.12). A joint test indicated differences in average PA measurements by HIV serostatus and VL (P = 0.001). However, differences by HIV serostatus in M10 and DTR were attenuated and no longer significant after adjustment for renal function, serum lipids, and depressive symptoms.

CONCLUSIONS

Physical activity measures differed significantly by HIV serostatus and VL. Higher L6 among PLWH with detectable VL may indicate reduced amount or quality of sleep compared to PLWH without detectable VL and PWOH. Lower M10 among PLWH indicates lower amounts of physical activity compared to PWOH.

Scalar on time-by-distribution regression and its application for modelling associations between daily-living physical activity and cognitive functions in Alzheimer's Disease

Wearable data is a rich source of information that can provide a deeper understanding of links between human behaviors and human health. Existing modelling approaches use wearable data summarized at subject level via scalar summaries in regression, temporal (time-of-day) curves in functional data analysis (FDA), and distributions in distributional data analysis (DDA). We propose to capture temporally local distributional information in wearable data using subject-specific time-by-distribution (TD) data objects. Specifically, we develop scalar on time-by-distribution regression (SOTDR) to model associations between scalar response of interest such as health outcomes or disease status and TD predictors. Additionally, we show that TD data objects can be parsimoniously represented via a collection of time-varying L-moments that capture distributional changes over the time-of-day. The proposed method is applied to the accelerometry study of mild Alzheimer’s disease (AD). We found that mild AD is significantly associated with reduced upper quantile levels of physical activity, particularly during morning hours. In-sample cross validation demonstrated that TD predictors attain much stronger associations with clinical cognitive scales of attention, verbal memory, and executive function when compared to predictors summarized via scalar total activity counts, temporal functional curves, and quantile functions. Taken together, the present results suggest that SOTDR analysis provides novel insights into cognitive function and AD.

Is Complexity of Daily Activity Associated with Physical Function and Life-Space Mobility among Older Adults?

PURPOSE

Information about mobility and physical function may be encoded in the complexity of daily activity pattern. Therefore, daily activity pattern complexity metrics could provide novel insight into the relationship between daily activity behavior and health. The purpose of the present study was to examine the association between the complexity of daily activity behavior and the mobility and physical function among community-dwelling older adults 75, 80, and 85 yr of age.

METHODS

A total of 309 participants wore accelerometers concurrently on the thigh and the trunk for at least three consecutive days. Five activity states (lying, sitting, standing, walking, or activity other than walking) were defined in three different temporal grains (5 s, 1 min, and 5 min), and Lempel-Ziv complexity was evaluated. We assessed complexity of daily activity behavior using the life-space mobility and physical function with distance in preferred pace 6-min walk and the Short Physical Performance Battery.

RESULTS

Weak positive associations were observed between the complexity of daily activity and the mobility and physical function at the finest temporal grains in both sexes (Spearman rho = 0.19 to 0.27, P < 0.05). No significant associations were observed in the coarsest temporal grain in either sex.

CONCLUSIONS

Lempel-Ziv estimates of daily activity complexity with a fine temporal grain seem to be associated with community-dwelling older adults' physical function. The coarsest 5-min temporal grain may have smoothed out physiologically meaningful short activity bouts. Because complexity encodes information related to timing, intensity, and patterning of behavior, complexity of activity could be an informative indicator of future physical function and mobility.

A semiparametric risk score for physical activity

We develop a generalized partially additive model to build a single semiparametric risk scoring system for physical activity across multiple populations. A score comprised of distinct and objective physical activity measures is a new concept that offers challenges due to the nonlinear relationship between physical behaviors and various health outcomes. We overcome these challenges by modeling each score component as a smooth term, an extension of generalized partially linear single-index models. We use penalized splines and propose two inferential methods, one using profile likelihood and a nonparametric bootstrap, the other using a full Bayesian model, to solve additional computational problems. Both methods exhibit similar and accurate performance in simulations. These models are applied to the National Health and Nutrition Examination Survey and quantify nonlinear and interpretable shapes of score components for all-cause mortality.

Genome-wide association studies of 27 accelerometry-derived physical activity measurements identified novel loci and genetic mechanisms

Physical inactivity (PA) is an important risk factor for a wide range of diseases. Previous genome-wide association studies (GWAS), based on self-reported data or a small number of phenotypes derived from accelerometry, have identified a limited number of genetic loci associated with habitual PA and provided evidence for involvement of central nervous system in mediating genetic effects. In this study, we derived 27 PA phenotypes from wrist accelerometry data obtained from 88,411 UK Biobank study participants. Single-variant association analysis based on mixed-effects models and transcriptome-wide association studies (TWAS) together identified 5 novel loci that were not detected by previous studies of PA, sleep duration and self-reported chronotype. For both novel and previously known loci, we discovered associations with novel phenotypes including active-to-sedentary transition probability, light-intensity PA, activity during different times of the day and proxy phenotypes to sleep and circadian patterns. Follow-up studies including TWAS, colocalization, tissue-specific heritability enrichment, gene-set enrichment and genetic correlation analyses indicated the role of the blood and immune system in modulating the genetic effects and a secondary role of the digestive and endocrine systems. Our findings provided important insights into the genetic architecture of PA and its underlying mechanisms.

Daily Physical Activity Patterns as a Window on Cognitive Diagnosis in the Baltimore Longitudinal Study of Aging (BLSA)

BACKGROUND

Gradual disengagement from daily physical activity (PA) could signal present or emerging mild cognitive impairment (MCI) or Alzheimer's disease (AD).

OBJECTIVE

This study examined whether accelerometry-derived patterns of everyday movement differ by cognitive diagnosis in participants of the Baltimore Longitudinal Study of Aging (BLSA).

METHODS

Activity patterns, overall and by time-of-day, were cross-sectionally compared between participants with adjudicated normal cognition (n = 549) and MCI/AD diagnoses (n = 36; 5 participants [14%] living with AD) using covariate-adjusted regression models.

RESULTS

Compared to those with normal cognition, those with MCI/AD had 2.1% higher activity fragmentation (SE = 1.0%, p = 0.036) but similar mean total activity counts/day (p = 0.075) and minutes/day spent active (p = 0.174). Time-of-day analyses show MCI/AD participants had lower activity counts and minutes spent active during waking hours (6:00 am-5:59 pm; p < 0.01 for all). Also, they had lower activity fragmentation from 12:00-5:59 am (p < 0.001), but higher fragmentation from 12:00-5:59 pm (p = 0.026).

CONCLUSION

Differences in the timing and patterns of physical activity throughout the day linked to MCI/AD diagnoses warrant further investigation into potential clinical utility.

Wrist-Worn Accelerometry, Aging, and Gait Speed in the Baltimore Longitudinal Study of Aging

Wrist-worn accelerometry metrics are not well defined in older adults. Accelerometry data from 720 participants (mean age 70 years, 55% women) were summarized into (a) total activity counts per day, (b) active minutes per day, (c) active bouts per day, and (d) activity fragmentation (the reciprocal of the mean active bout length). Linear regression and mixed-effects models were utilized to estimate associations between age and gait speed with wrist accelerometry. Activity counts per day, daily active minutes per day, and active bouts per day were negatively associated with age among all participants, while positive associations with activity fragmentation were only observed among those ≥65 years. More activity counts, more daily active minutes, and lower activity fragmentation were associated with faster gait speed. There were baseline age interactions with annual changes in total activity counts per day, active minutes per day, and activity fragmentation (Baseline age × Time, p < .01 for all). These results help define and characterize changes in wrist-based physical activity patterns among older adults.

Association of Combined Slow Gait and Low Activity Fragmentation With Later Onset of Cognitive Impairment

IMPORTANCE

Among older people, slow walking is an early indicator of risk for Alzheimer disease (AD). However, studies that have assessed this association have not considered that slow walking may have different causes, some of which are not necessarily associated with higher AD risk.

OBJECTIVE

To evaluate whether low activity fragmentation among older adults with slow gait speed indicates neurological causes of slow walking that put these individuals at higher risk of AD.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study performed survival analyses using data from the Baltimore Longitudinal Study of Aging. Participants included 520 initially cognitively normal persons aged 60 years or older. New diagnoses of mild cognitive impairment (MCI) or AD were adjudicated during a mean (SD) follow-up of 7.3 (2.7) years. Initial assessment of gait speed and activity fragmentation occurred from January 3, 2007, to May 11, 2015, with follow-up completed on December 31, 2020. Data were analyzed from February 1 to May 15, 2021.

EXPOSURES

Gait speed for 6 m and activity fragmentation assessed by accelerometry.

MAIN OUTCOMES AND MEASURES

Associations of gait speed, activity fragmentation, and their interaction with incident MCI/AD were evaluated using Cox proportional hazards models, adjusted for covariates.

RESULTS

Among the 520 participants (265 women [51.0%]; 125 Black participants [24.0%]; 367 White participants [70.6%]; mean [SD] age, 73 [8] years), MCI/AD developed in 64 participants. Each 0.05-m/s slower gait was associated with a 7% increase in risk of developing MCI/AD (hazard ratio [HR], 1.07 [95% CI, 1.00-1.15]; P = .04). Activity fragmentation alone was not associated with MCI/AD risk (HR, 0.83 [95% CI, 0.56-1.23]; P = .35), but there was a significant interaction between gait speed and activity fragmentation (HR, 0.92 [95% CI, 0.87-0.98]; P = .01). At low activity fragmentation (-1 SD), each 0.05-m/s slower gait speed was associated with a 19% increase in hazard of developing MCI/AD (HR, 1.19 [95% CI, 1.07-1.32]), whereas at higher activity fragmentation (+1 SD), gait speed was not associated with MCI/AD (HR, 1.01 [95% CI, 0.93-1.10]). Among participants with slow gait, higher activity fragmentation was associated with higher odds of having lower extremity osteoarthritis (odds ratio, 1.31 [95% CI, 1.01-1.69]) and less decline in pegboard dominant hand performance (β = 0.026 [SE, 0.009]; P > .05).

CONCLUSIONS AND RELEVANCE

These findings suggest that frequent rests among older adults with slow gait speed are associated with lower risk of future MCI/AD and that this behavioral strategy is associated with a lower likelihood of subclinical neurological impairment.

Personalized multicomponent exercise programs using smartphone technology among older people: protocol for a randomized controlled trial

BACKGROUND

Optimal application of the recently updated World Health Organization (WHO) guidelines for exercise in advanced age necessitates an accurate adjustment for the age-related increasing variability in biological age and fitness levels, alongside detailed recommendations across a range of motor fitness components, including balance, strength, and flexibility. We previously developed and validated a novel tool, designed to both remotely assess these fitness components, and subsequently deliver a personalized exercise program via smartphone. We describe the design of a prospective randomized control trial, comparing the effectiveness of the remotely delivered personalized multicomponent exercise program to either WHO exercise guidelines or no intervention.

METHODS

Participants (n = 300) are community dwelling, healthy, functionally independent, cognitively intact volunteers aged ≥65 at low risk for serious fall injuries, assigned using permuted block randomization (age/gender) to intervention, active-control, or control group. The intervention is an 8-week program including individually tailored exercises for upper/lower body, flexibility, strength, and balance (dynamic, static, vestibular); active-controls receive exercising counselling according to WHO guidelines; controls receive no guidance. Primary outcome is participant fitness level, operationalized as 42 digital markers generated from 10 motor fitness measures (balance, strength, flexibility); measured at baseline, mid-trial (4-weeks), trial-end (8-weeks), and follow-up (12-weeks). Target sample size is 300 participants to provide 99% power for moderate and high effect sizes (Cohen's f = 0.25, 0.40 respectively).

DISCUSSION

The study will help understand the value of individualized motor fitness assessment used to generate personalized multicomponent exercise programs, delivered remotely among older adults.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04181983.

Longitudinal changes in daily patterns of objectively measured physical activity after falls in older adults with varying degrees of glaucoma

BACKGROUND

Visually impaired older adults have a greater risk of falling, making them particularly susceptible to fall-related health consequences and restricted physical activity. Unclear however, is the relationship between having falls and longitudinal changes in daily patterns of objectively measured physical activity in older adults with visual impairments.

METHODS

We created a three-year prospective cohort study (Falls in Glaucoma Study) of older adults with primary or suspected glaucoma at the Johns Hopkins Wilmer Eye Institute from 2013 to 2015. Cumulative incidence of falls was determined through self-reported fall calendars over 12 months. Participants were then classified into one of three groups: multiple fallers (≥2 falls), single fallers (1 fall), and non-fallers (0). Daily physical activity was measured over 1 week using a waist-bound accelerometer during baseline and three-year follow-ups. Activity fragmentation was defined as the reciprocal of the mean activity bout length, with higher fragmentation reflecting shorter, more fractured bouts of continuous activity. Multivariate linear mixed-effects models were used to assess three-year longitudinal changes in: 1) activity fragmentation, and 2) accumulation of activity across six three-hour intervals from 5 AM to 11 PM.

FINDINGS

In adjusted models accounting for visual field damage and other factors, multiple fallers demonstrated greater annual declines (per year) in daily active bouts (-1.79 bouts/day, 95% confidence interval [CI]: -3.35, -0.22), daily active minutes (-17.15 min/day, 95% CI: -26.35, -7.94), and increased fragmentation (1%, 95% CI: 0, 2%) over the three-year follow-up period as compared to non-fallers; no such changes were seen when comparing single fallers and non-fallers. In time-of-day analyses, multiple fallers experienced greater annual declines in average hourly steps over all periods of the day, though the rate of decline was only significant between 5 PM and 8 PM (-27.07 steps/hour, 95% CI: -51.15, -2.99) compared to non-fallers.

INTERPRETATION

In an older population with visual impairment, multiple falls over 12 months were associated with more transient and fragmented activity over a subsequent three-year period, and activity declines during evening hours, compared to non-fallers. These findings suggest that multiple fallers with visual impairment may be at high risk for a decline in physical capacity and endurance, warranting clinical interventions.

FUNDING

The research was supported in part by National Institutes of Health Grant EY022976.

Objectively measured patterns of daily physical activity and phenotypic frailty

BACKGROUND

Self-reported low physical activity is a defining feature of phenotypic frailty but does not adequately capture physical activity performed throughout the day. This study examined associations between accelerometer-derived patterns of routine daily physical activity and frailty.

METHODS

Wrist accelerometer and frailty data from 638 participants (mean age 77 (SD=5.5) years; 44% women) were used to derive five physical activity metrics: active minutes/day, sedentary minutes/day, total activity counts/day, activity fragmentation (reciprocal of the average active bout length) and sedentary fragmentation (reciprocal of the average sedentary bout length). Robust, pre-frail and frail statuses were identified using the physical frailty phenotype defined as having 0, 1-2, or ≥3 of the following criterion: weight loss, exhaustion, slowness, self-reported low activity, and weakness. Frailty was collapsed into not frail (robust and prefrail) and frail, and each frailty criteria was dichotomized. Multiple logistic regression was used to model each accelerometer metric. Separate frailty criteria and interactions with age and sex were also examined.

RESULTS

With higher amounts and intensity of daily activity (more active minutes, fewer sedentary minutes, higher activity counts) and lower activity fragmentation, the odds of frailty were lower compared to robust/prefrail states (p<0.02 for all). For interactions, only an age by sedentary fragmentation interaction on the odds of frailty was observed (p=0.01). For each separate criteria, accelerometer metrics were associated with odds of slowness, low activity, and weakness.

CONCLUSION

Less favorable patterns of objectively measured daily physical activity are associated with frailty and the components of slowness, low self-reported activity, and weakness.

Personalized Exercise Programs Based upon Remote Assessment of Motor Fitness: A Pilot Study among Healthy People Aged 65 Years and Older

BACKGROUND

The World Health Organization has recently updated exercise guidelines for people aged >65 years, emphasizing the inclusion of multiple fitness components. However, without adequate recognition of individual differences, these guidelines may be applied using an approach that "one-size-fits-all." Within the shifting paradigm toward an increasingly personalized approach to medicine and health, it is apparent that fitness components display a significant age-related increase in variability. Therefore, it is both logical and necessary to perform an accurate individualized assessment of multiple fitness components prior to optimal prescription for a personalized exercise program.

OBJECTIVE

The aim of the study was to test the feasibility and effectiveness of a novel tool able to remotely assess balance, flexibility, and strength using smartphone sensors (accelerometer/gyroscope), and subsequently deliver personalized exercise programs via the smartphone.

METHODS

We enrolled 52 healthy volunteers (34 females) aged 65+ years, with normal cognition and low fall risk. Baseline data from remote smartphone fitness assessment were analyzed to generate 42 fitness digital markers (DMs), used to guide personalized exercise programs (×5/week for 6 weeks) delivered via smartphone. Programs included graded exercises for upper/lower body, flexibility, strength, and balance (dynamic, static, and vestibular). Participants were retested after 6 weeks.

RESULTS

Average age was 74.7 ± 6.4 years; adherence was 3.6 ± 1.7 exercise sessions/week. Significant improvement for pre-/posttesting was observed for 10/12 DMs of strength/flexibility for upper/lower body (sit-to-stand repetitions/duration; arm-lift duration; torso rotation; and arm extension/flexion). Balance improved significantly for 6/10 measures of tandem stance, with consistent (nonsignificant) trends observed across 20 balance DMs of tandem walk and 1 leg stance. Balance tended to improve among the 37 participants exercising ≥3/week.

DISCUSSION

These preliminary results provide a proof of concept, with high adherence and improved fitness confirming the benefits of remote fitness assessment for guiding home personalized exercise programs among healthy adults aged >65 years. Further examination of the application within a randomized control study is necessary, comparing the personalized exercise program to general guidelines among healthy older adults, as well as specific populations, such as those with frailty, deconditioning, cognitive, or functional impairment. The study tool offers the opportunity to collect big data, including additional variables, with subsequent utilization of artificial intelligence to optimize the personalized exercise program.

Variability in Hourly Activity Levels: Statistical Noise or Insight Into Older Adult Frailty?

BACKGROUND

Frailty is associated with lower mean activity; however, hourly activity is highly variable among older individuals. We aimed to relate frailty to hourly activity variance beyond frailty's association with mean activity.

METHOD

Using the 2010-2011 National Social Life, Health and Aging Project wrist accelerometry data (n = 647), we employed a mixed-effects location scale model to simultaneously determine whether an adapted phenotypic frailty scale (0-4) was associated with the log10-mean hourly counts per minute (cpm) and between-and within-subject hourly activity variability, adjusting for demographics, health characteristics, season, day-of-week, and time-of-day. We tested the significance of a Frailty × Time-of-day interaction and whether adjusting for sleep time altered relationships.

RESULTS

Each additional frailty point was associated with a 7.6% (10-0.0343, β = -0.0343; 95% CI: -0.05, -0.02) lower mean hourly cpm in the morning, mid-day, and late afternoon but not evening. Each frailty point was also associated with a 24.5% (e0.219, β = 0.219; 95% CI: 0.09, 0.34) greater between-subject hourly activity variance across the day; a 7% (e0.07, β = 0.07; 95% CI: 0.01¸ 0.13), 6% (e0.06, β = 0.06; 95% CI: 0, 0.12), and 10% (e0.091, β = 0.091; 95% CI: 0.03, 0.15) greater within-subject hourly activity variance in the morning, mid-day, and late afternoon, respectively; and a 6% (e-0.06, β = -0.06; 95% CI: -0.12, -0.003) lower within-subject hourly activity variance in the evening. Adjusting for sleep time did not alter results.

CONCLUSIONS

Frail adults have more variable hourly activity levels than robust adults, a potential novel marker of vulnerability. These findings suggest a need for more precise activity assessment in older adults.

Association Between Brain Volumes and Patterns of Physical Activity in Community-Dwelling Older Adults

BACKGROUND

Larger brain volumes are often associated with more free-living physical activity (PA) in cognitively normal older adults. Yet, whether greater brain volumes are associated with more favorable (less fragmented) PA patterns, and whether this association is stronger than with total PA, remains unknown.

METHODS

Brain magnetic resonance imaging and wrist-worn accelerometer data were collected in 301 participants (mean age = 77 [SD = 7] years, 59% women) enrolled in the Baltimore Longitudinal Study of Aging. Linear regression models were fit to examine whether brain volumes (cc) were cross-sectionally associated with: (a) total daily PA minutes and (b) activity fragmentation (mean number of PA bouts / total PA minutes × 100). Sensitivity analyses were conducted by adjusting for counterpart PA variables (eg, fragmentation covariate included in the PA minutes model).

RESULTS

Greater white matter volumes in the parietal and temporal lobes were associated with higher daily PA minutes (2.6 [SE = 1.0] and 3.8 [0.9] min/day, respectively; p < .009 for both) after adjusting for demographics, behavioral factors, medical conditions, gait speed, apolipoprotein E e4 status, and intracranial volume. Greater temporal white matter volume was associated with lower fragmentation (-0.16% [0.05], p = .003). In sensitivity analyses, observed associations between brain volumes and daily PA minutes remained significant while associations with fragmentation no longer remained significant.

CONCLUSIONS

Our results suggest white matter brain structure in cognitively normal older adults is associated with the total amount of PA and, to a lesser extent, the PA accumulation patterns. More work is needed to elucidate the longitudinal relationship between brain structure and function and PA patterns with aging.

Assessment of Physical Activity in Adults using Wrist Accelerometers

The health benefits of physical activity have been widely recognized, yet traditional measures of physical activity including questionnaires and category-based assessments of volume and intensity provide only broad estimates of daily activities. Accelerometers have advanced epidemiologic research on physical activity by providing objective and continuous measurement of physical activity in free-living conditions. Wrist-worn accelerometers have become especially popular due to low participant burden. However, the validity and reliability of wrist-worn devices for adults have yet to be summarized. Moreover, accelerometer data provide rich information on how physical activity is accumulated throughout the day, but only a small portion of these rich data have been utilized by researchers. Lastly, new methodological developments that aim to overcome some of the limitations of accelerometers are emerging. The purpose of this review is to provide an overview of accelerometry research, with a special focus on wrist-worn accelerometers. We describe briefly how accelerometers work, summarize the validity and reliability of wrist-worn accelerometers, discuss the benefits of accelerometers including measuring light-intensity physical activity, and discuss pattern metrics of daily physical activity recently introduced in the literature. A summary of large-scale cohort studies and randomized trials that implemented wrist-worn accelerometry is provided. We conclude the review by discussing new developments and future directions of research using accelerometers, with a focus on wrist-worn accelerometers.

Association between walking energetics and fragmented physical activity in mid-to-late life

BACKGROUND

Physical activity becomes increasingly fragmented with age, which may be an early marker of functional decline. Energetic cost of walking and energy capacity are also linked with functional decline, but their associations with activity fragmentation, and the potential modifying roles of total daily physical activity and age, remains unclear.

METHODS

493 participants (50-93 years) from the Baltimore Longitudinal Study of Aging underwent measures of: energetic cost of usual-paced overground walking (ml/kg/m), energy demand during slow walking (ml/kg/min) on a treadmill (0.67 m/s, 0% grade),m/s, 0% grade), and average peak walking energy expenditure (ml/kg/min) during a fast-paced 400-m walk. A ratio of slow walking to peak walking energy expenditure ("cost-to-capacity ratio") was calculated. Activity fragmentation was quantified as an active-to-sedentary transition probability (ASTP) using Actiheart accelerometer data. Linear regression models with ASTP as the dependent variable were used to test whether poorer energy cost and capacity were associated with higher ASTP and whether the associations differed by daily physical activity or age.

RESULTS

After adjusting for demographics, body composition, comorbidities and daily physical activity, every 10% higher cost-to-capacity ratio was associated with 0.4% greater ASTP (p=0.005). This association was primarily driven by the least active participants (pinteraction=0.023). Peak walking energy expenditure was only associated with ASTP among participants aged ≥70 years.

CONCLUSIONS

Higher cost-to-capacity ratio and lower energy capacity may manifest as more fragmented physical activity, especially among those less active or aged ≥70 years. Future studies should examine whether an increasing cost-to-capacity ratio or declining energy capacity predicts subsequent activity fragmentation.

Visual Impairment and Objectively Measured Physical Activity in Middle-Aged and Older Adults

BACKGROUND

Vision loss is associated with increased falls risk and restricted physical activity, yet the relationship between multiple vision measures and objectively measured physical activity, especially activity patterns, in mid-to-late life is not well understood.

METHODS

This study included 603 participants aged ≥ 50 years (mean age=73.5) in the Baltimore Longitudinal Study of Aging who had the following assessments: presenting and best-corrected visual acuity, contrast sensitivity, visual fields, stereo acuity, and free-living physical activity using a wrist-worn ActiGraph accelerometer for 7 days. Linear regression models were used to examine the association between vision measures and daily activity counts, active minutes, and activity fragmentation (defined as an active-to-sedentary transition probability), adjusting for potential confounders. Mixed-effects models estimated differences in activity by time of day comparing those with and without each visual impairment.

RESULTS

In the fully adjusted model, worse presenting visual acuity, contrast sensitivity, and visual fields were associated with fewer activity counts, less active time, and more fragmented activity patterns (p<0.05 for all). Participants with presenting or best-corrected visual acuity impairment had 19.2 and 29.3 fewer active minutes (p=0.05, p=0.03, respectively) per day. Visual field impairment was associated with 268,636 fewer activity counts (p=0.02), 46.2 fewer active minutes (p=0.02) per day, and 3% greater activity fragmentation (p=0.009). Differences in activity levels tended to be greatest from 6am-6pm (p<0.05).

CONCLUSIONS

Older adults with visual impairment have restricted and more fragmented patterns of daily activity. Longitudinal studies to quantify the long-term impacts of visual impairments on activity decline are warranted.

Lactoferrin for the treatment of age-associated inflammation - A pilot study

BACKGROUND

Chronic inflammation (CI) is a common trait of aging associated with adverse outcomes including mortality. We hypothesized that recombinant human Lactoferrin (rhLf) would reduce chronic inflammation of aging.

METHODS

Thirty-six community dwelling older adults were randomly assigned to rhLf or placebo treatment in 1:1 ratio for 3 months. IL-6, sTNFR1, Comprehensive Metabolic Panel (CMP), and Complete Blood Count (CBC) were measured at baseline, 1 month, 3 months, and 6 months. Physical and cognitive measures were completed at same timepoints, including 4-m walking speed (m/s), grip strength (kg), 6-min walking distance (m), home activity measured by accelerometer, trail making test - Part A (s) and - Part B (s), and Digit symbol substitution test (number correctly coded). Primary outcomes were differences in IL-6 and sTNFR1 concentrations evaluated by generalized linear model with log-link and gamma family distribution, controlling for baseline cytokine concentrations.

RESULTS

rhLF was well-tolerated. There were a significant number of abdominal complaints and increased drop-out rate in placebo group. Participants in rhLf arm had non-significant lower mean percent increase in IL6 at 3 months (rhLf mean IL-6 6% lower than control, P = 0.843), and sTNFaR1 (rhLf mean 2% lower than control, P = 0.36). No significant changes were observed for the cognitive or physical measures.

CONCLUSION

Treatment with rhLf did not significantly alter serum IL6 or sTNFR1 concentrations of older adults. This study may have been underpowered to detect difference, but provided evidence that a larger sample-size could more definitively determine the effect of rhLF on age-associated CI.