Fatigability: A Prognostic Indicator of Phenotypic Aging

Cross-cultural translation, validation, and responsiveness of the Pittsburgh Fatigability Scale - Italian version (PFS-I) in a mixed-sample of older adults

INTRODUCTION

Older adults experience fatigue which impacts health-related quality of life. The Pittsburgh Fatigability Scale (PFS) was specifically designed to assess perceived physical and mental fatigability in older adults. The aim of this study was to translate the PFS into Italian (PFS-I) and to investigate its psychometric properties.

METHODS

The PFS-I was translated in accordance with international standards. The following properties were evaluated: structural validity, internal consistency, hypotheses testing for construct validity, test-retest reliability using intraclass correlation coefficients (ICC), and minimal clinically important difference (MCID) for responsiveness.

RESULTS

The study included 87 older adults with cardiovascular/respiratory diseases (CVRD), 46 with Parkinson disease (PD), and 67 healthy controls (HC). The PFS-I Physical and Mental subscales scores were significantly different in these populations, with HC reporting the lowest fatigability. Exploratory and confirmatory factor analysis showed a two-factor structure for both subscales, with good internal consistency (Cronbach's alpha: 0.86 and 0.89, respectively). The PFS-I Physical subscale showed weak goodness-of-fit of the confirmatory factor analysis models, whereas the PFS-I Mental subscale was deemed acceptable. Construct validity of the PFS-I was excellent with 75% (18 out of 24) of hypotheses accepted. Test-retest reliability was analyzed in a subset of 23 patients with CVRD and showed excellent results for both the PFS-I Physical and Mental subscales (ICC = 0.93 and 0.92, respectively). MCID ranged between 6 and 7 points for the Physical and 7-9 points for the Mental subscale.

CONCLUSIONS

The PFS-I is a valid, reliable, and responsive instrument to assess perceived fatigability for healthy older adults as well as those with CRVD and PD.

Sex differences in the association between skeletal muscle energetics and perceived physical fatigability: the Study of Muscle, Mobility and Aging (SOMMA)

Greater perceived physical fatigability and lower skeletal muscle energetics are both predictors of mobility decline. Characterizing associations between muscle energetics and perceived fatigability may provide insight into potential targets to prevent mobility decline. We examined associations of in vivo (maximal ATP production, ATPmax) and ex vivo (maximal carbohydrate supported oxidative phosphorylation [max OXPHOS] and maximal fatty acid supported OXPHOS [max FAO OXPHOS]) measures of mitochondrial energetics with two measures of perceived physical fatigability, Pittsburgh Fatigability Scale (PFS, 0-50, higher = greater) and Rating of Perceived Exertion (RPE Fatigability, 6-20, higher = greater) after a slow treadmill walk. Participants from the Study of Muscle, Mobility and Aging (N = 873) were 76.3 ± 5.0 years old, 59.2% women, and 85.3% White. Higher muscle energetics (both in vivo and ex vivo) were associated with lower perceived physical fatigability, all p < 0.03. When stratified by sex, higher ATPmax was associated with lower PFS Physical for men only; higher max OXPHOS and max FAO OXPHOS were associated with lower RPE Fatigability for both sexes. Higher skeletal muscle energetics were associated with 40-55% lower odds of being in the most (PFS ≥ 25, RPE Fatigability ≥ 12) vs least (PFS 0-4, RPE Fatigability 6-7) severe fatigability strata, all p < 0.03. Being a woman was associated with 2-3 times higher odds of being in the most severe fatigability strata when controlling for ATPmax but not the ex vivo measures (p < 0.05). Better mitochondrial energetics were linked to lower fatigability and less severe fatigability in older adults. Findings imply that improving skeletal muscle energetics may mitigate perceived physical fatigability and prolong healthy aging.

Perceived physical and mental fatigability in older adults with and without multiple sclerosis

BACKGROUND

Fatigue stands out as a prevalent and debilitating symptom in both Multiple Sclerosis (MS) and the aging population. Traditional methods for measuring perceived fatigue may not adequately account for individual activity differences, leading to varied prevalence rates. Perceived fatigability anchors fatigue to specific activities with predetermined intensity and duration, thereby mitigating self-pacing bias. Despite its potential, perceived fatigability is poorly understood in older adults, particularly those with neurological conditions, including MS. This study thus aimed to (1) investigate whether, among older adults, MS was associated with worse perceived physical and mental fatigability; (2) evaluate whether, among older adults with MS (OAMS), greater patient-reported disease-related disability was associated with worse perceived physical and mental fatigability.

METHODS

Participants were 96 older adults with a physician-confirmed diagnosis of MS (mean age: 64.6 ± 4.2) and 110 healthy controls (mean age: 68.2 ± 7.2), all confirmed to be dementia-free through established case conference procedures. Physical and mental fatigability were measured using the Pittsburgh Fatigability Scale, a 10-item questionnaire (score range: 0 to 50) designed to assess fatigue levels that individuals expect to feel after engaging in a range of typical activities for older adults. MS disease-related disability was assessed with the Patient Determined Disease Steps scale, which ranges from 0 (normal) to 8 (bedridden), with scores ≥ 2 indicating worse MS-related disability after a median split. Separate linear regression models were performed to investigate associations between group status (MS vs. Control) as the predictor and perceived physical and mental fatigability scores as the outcome variables. Within the MS group, additional linear regression models were performed to explore the relationship between disease-related disability and fatigability levels. All models adjusted for age, sex, race, education, global health, general cognitive function, and depressive symptoms levels.

RESULTS

The fully adjusted models yielded the following key findings: OAMS reported significantly higher levels of perceived physical fatigability (M = 25.11 ± 9.67) compared to controls (M = 17.95 ± 8.35) (p = 0.003). Similarly, the perceived mental fatigability in OAMS (M = 16.82 ± 11.79) was significantly greater than that in controls (M = 9.15 ± 7.12) (p = 0.003). Within the MS group, individuals with greater disease-related disability reported significantly greater levels of both physical (M = 30.13 ± 7.71 vs. 18.67 ± 8.00, p < 0.001) and mental fatigability (M = 20.31 ± 12.18 vs. 12.33 ± 9.69, p = 0.009) compared to those with lower MS-related disability. Of note, the significance of these findings persisted in models that adjusted for depressive symptoms.

CONCLUSION

Our study provides compelling evidence that OAMS exhibit significantly higher perceived physical and mental fatigability compared to healthy controls. Additionally, worse MS-related disability correlates with worse physical and mental fatigability. These results persist after adjusting for confounders including depressive symptoms. Our findings underscore the necessity of holistic management strategies that cater to both physical and psychological aspects of MS, laying a foundation for future studies to uncover the pathophysiological mechanisms of fatigability in older adults with and without MS.

Comparing Sarcopenia Definitions and Muscle Power Reduction: Associations with Health Outcomes in Spanish Community-Dwelling Older Adults

Objectives: To analyze the associations between the different operational definitions of sarcopenia published in the last decade and reduced muscle power with a set of adverse health-related outcomes, such as comorbidities, depression, polypharmacy, self-perceived health, educational attainment, socioeconomic status, falls, and hospitalizations in Spanish community-dwelling older adults. Methods: A total of 686 community-dwelling older adults (median age: 72; women: 59.2%; physically active: 84%) were included in this cross-sectional analysis (ClinicalTrials.gov: NCT05148351). Sarcopenia was assessed using the FNIH, EWGSOP2, AWGS, and SDOC algorithms. Reduced muscle power was defined as the lowest sex-specific tertile and measured during the rising phase of the sit-to-stand test using a validated mobile application. Unadjusted and adjusted logistic regressions by potential confounders were performed to identify the association between sarcopenia and reduced muscle power with health-related outcomes. Results: Sarcopenia prevalence was 3.4%, 3.8%, 12.4%, and 21.3% according to the SDOC, FNIH, EWGSOP2, and AWGS, respectively. Among these definitions, moderate and large associations with health-related outcomes were observed for EWGSOP2 and SDOC, respectively, but few associations were found for FNIH and AWGS criteria. Reduced muscle power was associated more frequently and moderately with health-related outcomes compared to sarcopenia definitions. These associations remained constant after adjusting for confounders. Conclusions: The prevalence and impact of sarcopenia varied depending on the definitions used. Among the sarcopenia definitions, the SDOC exhibited the strongest associations, while reduced muscle power was the variable most frequently associated with health-related outcomes compared to any of the four sarcopenia definitions in well-functioning and physically active community-dwelling older adults.

Associations between skeletal muscle energetics and accelerometry-based performance fatigability: Study of Muscle, Mobility and Aging

Performance fatigability is typically experienced as insufficient energy to complete daily physical tasks, particularly with advancing age, often progressing toward dependency. Thus, understanding the etiology of performance fatigability, especially cellular-level biological mechanisms, may help to delay the onset of mobility disability. We hypothesized that skeletal muscle energetics may be important contributors to performance fatigability. Participants in the Study of Muscle, Mobility and Aging completed a usual-paced 400-m walk wearing a wrist-worn ActiGraph GT9X to derive the Pittsburgh Performance Fatigability Index (PPFI, higher scores = more severe fatigability) that quantifies percent decline in individual cadence-versus-time trajectory from their maximal cadence. Complex I&II-supported maximal oxidative phosphorylation (max OXPHOS) and complex I&II-supported electron transfer system (max ETS) were quantified ex vivo using high-resolution respirometry in permeabilized fiber bundles from vastus lateralis muscle biopsies. Maximal adenosine triphosphate production (ATPmax) was assessed in vivo by 31P magnetic resonance spectroscopy. We conducted tobit regressions to examine associations of max OXPHOS, max ETS, and ATPmax with PPFI, adjusting for technician/site, demographic characteristics, and total activity count over 7-day free-living among older adults (N = 795, 70-94 years, 58% women) with complete PPFI scores and ≥1 energetics measure. Median PPFI score was 1.4% [25th-75th percentile: 0%-2.9%]. After full adjustment, each 1 standard deviation lower max OXPHOS, max ETS, and ATPmax were associated with 0.55 (95% CI: 0.26-0.84), 0.39 (95% CI: 0.09-0.70), and 0.54 (95% CI: 0.27-0.81) higher PPFI score, respectively. Our findings suggested that therapeutics targeting muscle energetics may potentially mitigate fatigability and lessen susceptibility to disability among older adults.

Sex Differences in the Association between Skeletal Muscle Energetics and Perceived Physical Fatigability: The Study of Muscle, Mobility and Aging (SOMMA)

Greater perceived physical fatigability and lower skeletal muscle energetics are predictors of mobility decline. Characterizing associations between muscle energetics and perceived fatigability may provide insight into potential targets to prevent mobility decline. We examined associations of in vivo (maximal ATP production, ATPmax) and ex vivo (maximal carbohydrate supported oxidative phosphorylation [max OXPHOS] and maximal fatty acid supported OXPHOS [max FAO OXPHOS]) measures of mitochondrial energetics with two measures of perceived physical fatigability, Pittsburgh Fatigability Scale (PFS, 0-50, higher=greater) and Rating of Perceived Exertion (RPE Fatigability, 6-20, higher=greater) after a slow treadmill walk. Participants from the Study of Muscle, Mobility and Aging (N=873) were 76.3±5.0 years old, 59.2% women, and 85.3% White. Higher muscle energetics (both in vivo and ex vivo ) were associated with lower perceived physical fatigability, all p<0.03. When stratified by sex, higher ATPmax was associated with lower PFS Physical for men only; higher max OXPHOS and max FAO OXPHOS were associated with lower RPE fatigability for both sexes. Higher skeletal muscle energetics were associated with 40-55% lower odds of being in the most (PFS≥25, RPE Fatigability≥12) vs least (PFS 0-4, RPE Fatigability 6-7) severe fatigability strata, all p<0.03. Being a woman was associated with 2-3 times higher odds of being in the most severe fatigability strata when controlling for ATPmax but not the in vivo measures (p<0.05). Better mitochondrial energetics were linked to lower fatigability and less severe fatigability in older adults. Findings imply that improving skeletal muscle energetics may mitigate perceived physical fatigability and prolong healthy aging.

Association between fatigue, peripheral serotonin, and L-carnitine in hypothyroidism and in chronic fatigue syndrome

Background

Fatigue of unknown origin is a hallmark symptom in chronic fatigue syndrome (CFS) and is also found in 20% of hypothyroidism patients despite appropriate levothyroxine treatment. Here, we suggest that in these disorders, peripheral serotonin levels are low, and elevating them to normal range with L-carnitine is accompanied with reduced fatigue.

Methods

We conducted a retrospective analysis of follow-up clinical data (CFS N=12; hypothyroidism with fatigue N=40) where serum serotonin and fatigue levels were compared before vs. after 7 weeks of oral L-carnitine supplementation.

Results

After L-carnitine, serotonin increased (8-fold in CFS, Sig. = 0.002, 6-fold in hypothyroidism, Sig. < 0.001) whereas fatigue decreased (2-fold in both CFS and hypothyroidism, Sig. = 0.002 for CFS, Sig. < 0.001 for hypothyroidism). There was a negative correlation between serotonin level and fatigue (for CFS, rho = -0.49 before and -0.67 after L-carnitine; for hypothyroidism, rho = -0.24 before and -0.83 after L-carnitine).

Conclusions

These findings suggest a new link between low peripheral serotonin, L-carnitine, and fatigue.

Perceived Fatigability, Fatigue, and Mortality in Mid-to-Late Life in the Baltimore Longitudinal Study of Aging

INTRODUCTION/PURPOSE

Fatigue is an established prognostic indicator of mortality risk. It remains unknown whether fatigability anchored to a physical task is a more sensitive prognostic indicator and whether sensitivity differs by prevalent chronic conditions.

METHODS

A total of 1076 physically well-functioning participants 50 yr or older in the Baltimore Longitudinal Study of Aging self-reported fatigue (unusual tiredness or low energy) and had perceived fatigability assessed after a standardized treadmill walk. All-cause mortality was ascertained by proxy contact and National Death Index linkage. Cox proportional hazards models estimated associations of perceived fatigability and fatigue with all-cause mortality, adjusting for demographic and clinical covariates. Interactions by chronic conditions were also examined.

RESULTS

Each 1 SD higher in perceived fatigability, unusual tiredness, or low energy was associated with a higher relative hazard of all-cause mortality after covariate adjustment (fatigability: hazard ratio (HR), 1.18 (95% confidence interval (CI), 1.03-1.36); unusual tiredness: HR, 1.25 (95% CI, 1.08-1.44); low energy: HR, 1.27 (95% CI, 1.10-1.46)). Models had similar discrimination ( P > 0.14 for all). Perceived fatigability was associated with mortality risk among participants free of arthritis or osteoarthritis who otherwise appeared healthy (no arthritis: HR, 1.45 (95% CI, 1.15-1.84); arthritis: HR, 1.09 (95% CI, 0.92-1.30); P -interaction = 0.031). Unusual tiredness was associated with mortality among those with a history of diabetes (no diabetes: HR, 1.16 (95% CI, 0.97-1.38); diabetes: HR, 1.65 (95% CI, 1.22-2.23); P -interaction = 0.045) or pulmonary disease (no pulmonary disease: HR, 1.22 (95% CI, 1.05-1.43); pulmonary disease: HR, 2.15 (95% CI, 1.15-4.03); P -interaction = 0.034).

CONCLUSIONS

Higher perceived fatigability and fatigue symptoms were similarly associated with higher all-cause mortality, but utility differed by chronic condition. Perceived fatigability might be useful for health screening and long-term mortality risk assessment for well-functioning adults. Alternatively, self-reported fatigue seems more disease-specific with regard to mortality risk.

The association between frailty and perceived physical and mental fatigability: The Long Life Family Study

BACKGROUND

Higher levels of frailty, quantified by a frailty index (FI), may be linked to fatigue severity as tasks become more physically and mentally demanding. Fatigue, a component of frailty research, has been ambiguous and inconsistent in its operationalization. Fatigability-the quantification of vulnerability to fatigue in relation to specific intensity and duration of activities-offers a more sensitive and standardized approach, though the association between frailty and fatigability has not been assessed.

METHODS

Using cross-sectional data from the Long Life Family Study at Visit 2 (2014-2017; N = 2524; mean age ± standard deviation (SD) 71.4 ± 11.2 years; 55% women; 99% White), we examined associations between an 83-item FI after excluding fatigue items (ratio of number of health problems reported (numerator) out of the total assessed (denominator); higher ratio = greater frailty) and perceived physical and mental fatigability using the Pittsburgh Fatigability Scale (PFS) (range 0-50; higher scores = greater fatigability).

RESULTS

Participants had mean ± standard deviation FI (0.08 ± 0.06; observed range: 0.0-0.43), PFS Physical (13.7 ± 9.6; 39.5% more severe, ≥15), and PFS Mental (7.9 ± 8.9; 22.8% more severe, ≥13). The prevalence of more severe physical and mental fatigability was higher across FI quartiles. In mixed effects models accounting for family structure, a clinically meaningful 3%-higher FI was associated with 1.9 points higher PFS Physical score (95% confidence interval (CI) 1.7-2.1) and 1.7 points higher PFS Mental score (95% CI 1.5-1.9) after adjusting for covariates.

CONCLUSIONS

Frailty was associated with perceived physical and mental fatigability severity. Understanding this association may support the development of interventions to mitigate the risks associated with greater frailty and perceived fatigability. Including measurements of perceived fatigability, in lieu of fatigue, in frailty indices has the potential to alleviate the inconsistencies and ambiguity surrounding the operationalization of fatigue and provide a more precise and sensitive measurement of frailty.

Measuring and Understanding the Health Impact of Greater Fatigability in Older Adults: A Call to Action and Opportunities

Different from fatigue, an instantaneous state of tiredness, weakness and lack of energy, fatigability is a trait that contextualizes whole-body fatigue to the level of activity (i.e., intensity and duration) with which the fatigue is associated. Fatigability can be perceived or performance-related. Measuring fatigability improves upon traditional fatigue measures by accounting for self-pacing as older adults likely slow down or limit their daily activity to maintain fatigue in a tolerable range. Anchoring fatigue to activities/tasks improves sensitivity and allows for meaningful comparisons across individuals/between studies, as well as evaluating change over time and treatment effects. Two well-validated approaches are utilized to measure perceived fatigability: 1) a 5-minute slow-paced (1.5 mph/0.67 m/s, 0% grade) treadmill walk immediately followed by Borg rating of perceived exertion; and 2) a self-administered 10-item questionnaire, Pittsburgh Fatigability Scale, with both physical and mental subscales. Many walking-based performance fatigability measures are based on certain lap time or distance, while the Pittsburgh Performance Fatigability Index uses raw accelerometry data to quantify percent of cadence decline over the entire long distance walking tasks. Perceived fatigability prevalence ranges from 20-90% in older adults varying by assessment tool, and is higher with advancing age and in women compared to men. Fatigability is associated with physical and cognitive function, fall risk, mobility decline, and mortality. Unfortunately, the available research lacks representativeness in terms of racial and ethnic diversity. The time is now to incorporate our established sensitive and validated fatigability measures into global research and clinical practice to better understand mechanistic underpinnings and reveal intervention effects to reduce the burden and lessen the consequences of greater fatigability worldwide.

Role of Perceived Physical and Mental Fatigability Severity on Prospective, Recurrent, and Injurious Fall Risk in Older Men

BACKGROUND

Falls occur annually in 25% of adults aged ≥65 years. Fall-related injuries are increasing, highlighting the need to identify modifiable risk factors.

METHODS

Role of fatigability on prospective, recurrent, and injurious fall risk was examined in 1 740 men aged 77-101 years in the Osteoporotic Fractures in Men Study. The 10-item Pittsburgh Fatigability Scale measured perceived physical and mental fatigability (0-50/subscale) at Year 14 (2014-16); established cut-points identified men with more severe perceived physical (≥15, 55.7%), more severe mental (≥13, 23.7%) fatigability, or having both (22.8%). Prospective, recurrent (≥2), and injurious falls were captured by triannual questionnaires ≥1 year after fatigability assessment; risk of any fall was estimated with Poisson generalized estimating equations, and likelihood of recurrent/injurious falls with logistic regression. Models adjusted for age, health conditions, and other confounders.

RESULTS

Men with more severe physical fatigability had a 20% (p = .03) increased fall risk compared with men with less physical fatigability, with increased odds of recurrent and injurious falls, 37% (p = .04) and 35% (p = .035), respectively. Men with both more severe physical and mental fatigability had a 24% increased risk of a prospective fall (p = .026), and 44% (p = .045) increased odds of recurrent falling compared with men with less severe physical and mental fatigability. Mental fatigability alone was not associated with fall risk. Additional adjustment for previous fall history attenuated associations.

CONCLUSIONS

More severe fatigability may be an early indicator to identify men at high risk for falls. Our findings warrant replication in women, as they have higher rates of fatigability and prospective falls.

Dual Roles of Cardiorespiratory Fitness and Fatigability in the Life-Space Mobility of Older Adults: The Study of Muscle, Mobility and Aging (SOMMA)

BACKGROUND

Cardiorespiratory fitness and perceived fatigability are interrelated components of physical capacity that may jointly influence movement within one's living environment (life-space mobility). We examined whether fitness and fatigability were associated with life-space mobility in community-dwelling older adults, and whether the association of fitness with life-space varied by the level of perceived fatigability.

METHODS

Participants were from the Study of Muscle, Mobility and Aging (SOMMA) baseline cohort (N = 775, mean age 76.1 years). Life Space Assessment scores incorporated level, frequency, and assistance used (personal, devices) for life-space mobility. Fitness was measured as VO2peak from symptom-limited treadmill testing. Fatigability cut-points included: (i) Borg Rating of Perceived Exertion (RPE) ≥ 10 after a fixed-speed (1.5 mph) treadmill test, (ii) the Pittsburgh Fatigability Scale (PFS) Physical ≥ 15, and (iii) PFS Mental ≥ 13. The total count of cut-points was used as a composite fatigability measure (range: 0-3). Linear regressions were adjusted for demographic, lifestyle, and health confounders.

RESULTS

Better fitness was associated with greater life-space, but the association plateaued at higher fitness levels (VO2peak > 18). Life-space was significantly lower for individuals meeting ≥2 fatigability criteria (vs none), attributable mainly to more severe physical, but not mental, fatigability. In moderation analyses, the fitness-life-space association was significant only for those with RPE ≥ 10 but did not differ by PFS.

CONCLUSION

Fitness below a critically low threshold was associated with limited life-space mobility, suggesting that certain older individuals may need to operate close to their maximum aerobic capacity to traverse daily environments; these associations were driven by those with more severe physical fatigability.

Cognitive challenge as a probe to expose sex- and age-related differences during static contractions

Despite activities of daily living being frequently performed simultaneously with a cognitive task, motor function is often investigated in isolation, which can hinder the applicability of findings. This brief review presents evidence that 1) performing a cognitive challenge simultaneously with a motor task can negatively impact force steadiness and fatigability of limb muscles during a static contraction, 2) the negative impact on old adults (>65 years old), particularly older women is greater than young when a cognitive challenge is simultaneously performed with a static motor task, 3) age-related mechanisms potentially explain impairments in motor performance in the presence of a cognitive challenge, and 4) the mechanisms for the age-related decrements in motor performance can be distinct between men and women. These observations are highly relevant to the older adults, given the increased risk of accidents and injury when a motor task is performed with a high cognitive-demand task, especially in light of the expanding reliance on an aging workforce.

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.

Association of leukocyte telomere length with perceived physical fatigability

BACKGROUND

Leukocyte telomere length (LTL) is a potential genomic marker of biological aging, but its relation to fatigability, a prognostic indicator of phenotypic aging (e.g., functional decline) is unknown. We hypothesized shorter LTL would predict greater perceived physical fatigability, but that this association would be attenuated by adjusting for chronological age.

METHODS

Two generations of participants (N = 1997; 309 probands, 1688 offspring) were from the Long Life Family Study (age = 73.7 ± 10.4, range 60-108, 54.4 % women), a longitudinal cohort study of aging. LTL was assayed at baseline. Perceived physical fatigability was measured 8.0 ± 1.1 years later using the validated, self-administered 10-item Pittsburgh Fatigability Scale (PFS, 0-50, higher scores = greater fatigability). Generalized estimating equations were generated to model the association between LTL and PFS Physical scores.

RESULTS

Prevalence of greater physical fatigability (PFS scores≥15) was 41.9 %. Using generalized estimating equations, a one kilobase pair shorter LTL was associated with higher PFS Physical scores (β = 1.8, p < .0001), accounting for family structure, and adjusting for field center, follow-up time, sex, and follow-up body mass index, physical activity, and chronic health conditions. When age was included as a covariate, the association was fully attenuated (β = 0.1, p = .78).

CONCLUSION

LTL may provide an alternative method for estimating an individual's lifetime exposure to chronic stressors, but does not appear to provide additional information not captured by chronological age. Further research is needed to characterize the interaction between age, LTL, and perceived fatigability, and develop a method of identifying individuals at risk for deleterious aging.

Life-space Mobility in Older Men: The Role of Perceived Physical and Mental Fatigability

BACKGROUND

Physical performance and fatigue can limit mobility within the larger environment (life-space mobility). It is unknown whether perceived fatigability, self-reported fatigue anchored to activity intensity and duration, is independently associated with life-space.

METHODS

We assessed this cross-sectionally in Visit 4 (2014-2016) of the Osteoporotic Fractures in Men Study (MrOS; N = 1 672, Age: Mean = 84.2 ± 4.0 years). The Pittsburgh Fatigability Scale (PFS, range: 0-50; higher = greater fatigability) measured physical (Mean = 16.1 ± 9.4) and mental fatigability (Mean = 7.5 ± 7.9). Life Space Assessment scores incorporated level, frequency, and assistance used for life-space mobility (range: 0-120, higher = greater life-space mobility; life-space constriction: inability to leave neighborhood without assistance). Separate multiple linear and logistic regressions for physical and mental fatigability were sequentially adjusted for demographic, health/lifestyle, and performance measures.

RESULTS

The mean life-space mobility score was 84.6 ± 21.8, and 18% (n = 296) of men had life-space constriction. Higher physical and mental fatigability were both associated with lower life-space mobility in models adjusted for health and lifestyle factors (Physical PFS: B = -2.37, 95% confidence interval [CI]: [-3.39, -1.35]; Mental PFS: B = -1.79, 95% CI: [-2.73, -0.84]). Men with higher fatigability also had increased risk of life-space constriction (Physical PFS: OR = 1.59, 95% CI: [1.32, 1.92]; Mental PFS: OR = 1.25, 95% CI: [1.08, 1.46]). Associations were larger in magnitude for physical versus mental fatigability. Adjusting for physical performance measures more strongly attenuated associations for physical compared to mental fatigability.

CONCLUSIONS

Fatigability is linked with real-world mobility in older men, independent of their physical health. This association may be driven by separate physical and cognitive mechanisms worth examining further in longitudinal studies.

Development of a Novel Accelerometry-Based Performance Fatigability Measure for Older Adults

INTRODUCTION

Efforts to study performance fatigability have been limited because of measurement constrains. Accelerometry and advanced statistical methods may enable us to quantify performance fatigability more granularly via objective detection of performance decline. Thus, we developed the Pittsburgh Performance Fatigability Index (PPFI) using triaxial raw accelerations from wrist-worn accelerometer from two in-laboratory 400-m walks.

METHODS

Sixty-three older adults from our cross-sectional study (mean age, 78 yr; 56% women; 88% White) completed fast-paced ( n = 59) and/or usual-paced 400-m walks ( n = 56) with valid accelerometer data. Participants wore ActiGraph GT3X+ accelerometers (The ActiGraph LLC, Pensacola, FL) on nondominant wrist during the walking task. Triaxial raw accelerations from accelerometers were used to compute PPFI, which quantifies percentage of area under the observed gait cadence-versus-time trajectory during a 400-m walk to a hypothetical area that would be produced if the participant sustained maximal cadence throughout the entire walk.

RESULTS

Higher PPFI scores (higher score = greater fatigability) correlated with worse physical function, slower chair stands speed and gait speed, worse cardiorespiratory fitness and mobility, and lower leg peak power (| ρ | = 0.36-0.61 from fast-paced and | ρ | = 0.28-0.67 from usual-paced walks, all P < 0.05). PPFI scores from both walks remained associated with chair stands speed, gait speed, fitness, and mobility, after adjustment for sex, age, race, weight, height, and smoking status; PPFI scores from the fast-paced walk were associated with leg peak power.

CONCLUSIONS

Our findings revealed that the objective PPFI is a sensitive measure of performance fatigability for older adults and can serve as a risk assessment tool or outcome measure in future studies and clinical practice.

Translation and linguistic validation of the Pittsburgh Fatigability Scale for Korean breast cancer survivors: A cognitive interviewing study

Background

Fatigability-the perception of fatigue contextualized to activities of fixed intensity and duration-has received growing attention in oncology research.

Objectives

This study aimed to translate and linguistically validate a Korean-language version of the Pittsburgh Fatigability Scale.

Methods

Following the Linguistic Validation Manual for Health Outcome Assessment, we applied a multi-stage cognitive interviewing (CI) method to ensure accurate translation and interpretation of the Pittsburgh Fatigability Scale. After forward- and backward-translation were completed, three rounds of CI regarding the translated instrument were performed with 18 participants having or not having breast cancer.

Results

The first round of CI showed that seven items of the 10-item Korean-language instrument required revision to reflect the physical abilities of breast cancer patients with similar levels of physical activity. After the second round, two additional items were revised to reflect the cultural context and gender roles. During the third round, all participants exhibited full understanding of the Korean-language instrument.

Conclusions

The translated instrument, its quality enriched by cross-cultural linguistic validation in combination with CI, can be effectively used to assess perceived physical and mental fatigability.

Implications for Practice

Use of the Pittsburgh Fatigability Scale can facilitate oncology nurses' assessment of perceived fatigue levels in cancer patients and can expand understanding of how patients' fatigue perceptions are related to their exercise capacity.

Foundational

This study is valuable as an example of how a multi-stage CI process can be effectively applied in cross-cultural oncology research.

Age-related performance fatigability: a comprehensive review of dynamic tasks

Adult ageing is associated with a myriad of changes within the neuromuscular system, leading to reductions in contractile function of old adults. One of the consequences of these age-related neuromuscular adaptations is altered performance fatigability, which can limit the ability of old adults to perform activities of daily living. Whereas age-related fatigability of isometric tasks has been well characterized, considerably less is known about fatigability of old adults during dynamic tasks involving movement about a joint, which provides a more functionally relevant task compared to static contractions. This review provides a comprehensive summary of age-related fatigability in dynamic contractions, where the importance of task specificity is highlighted with a brief discussion of the potential mechanisms responsible for differences in fatigability between young and old adults. The angular velocity of the task is critical for evaluating age-related fatigability, as tasks which constrain angular velocity (i.e., isokinetic) produce equivocal age-related differences in fatigability, whereas tasks involving unconstrained velocity (i.e., isotonic-like) consistently induce greater fatigability of old compared to young adults. These unconstrained velocity tasks, that are more closely associated with natural movements, offer an excellent model to uncover the underlying age-related mechanisms of increased fatigability. Future work evaluating the mechanisms of increased age-related fatigability of dynamic tasks should be evaluated using task-specific contractions (i.e., dynamic), particularly for assessment of spinal and supra-spinal components. Advancing our understanding of age-related fatigability is likely to yield novel insights and approaches for improving mobility limitations in old adults.

Influence of an Upper Limb Isometric Task in Perceived and Performance Fatigability of Elderly Subjects: A Quasi-Experimental Study

Isometric activity can be used as a strategy to improve health, fitness, and functional performance in the elderly population, but differences in fatigability may occur. This study aimed to understand fatigability behavior during an upper limb isometric task (ULIT) and the role of health status and physical activity in the fatigability of elderly participants. Thirty-two (32) elderly participants (72.5 ± 5.18 years) were instructed to perform ULIT. The Borg CR10 scale and task failure point (TTF) were used to measure perceived and performance fatigability. Self-reported measures were used to assess the quality of life and physical activity level. A significant relationship between perceived and performance fatigability was found only in the final phase of activity (p < 0.01). Significant correlations were found between perceived fatigability and the social functioning dimension (p < 0.05), and between performance fatigability (TTF) and BMI (p < 0.01), physical functioning (p < 0.01), and role functioning/physical (p < 0.05) dimensions. In conclusion, ULIT produces changes in fatigability of elderly people, which are positively related in the final stage of the activity. Changes in fatigability are negatively related to BMI. It is also negatively related to health, social functioning, physical functioning and role functioning/physical quality of life dimensions.

Relationship Between Personality Measures and Perceived Mental Fatigability

OBJECTIVE

Examine the association between personality measures and perceived mental fatigability.

METHODS

We performed a cross-sectional analysis in N=1670 men, age 84.3±4.1 years. Multivariable linear regression models were used to examine the covariate adjusted association between personality measures (conscientiousness, optimism, goal reengagement, and goal disengagement) and perceived mental fatigability (measured with the validated 10-item Pittsburgh Fatigability Scale, PFS).

RESULTS

One standard deviation lower conscientiousness (β=-0.91, p<.0001) and optimism (β=-0.63, p<.0001), and higher goal reengagement (β=0.51, p=.01) scores were independently associated with higher PFS Mental scores adjusted for age, cognitive function, self-reported health status, depressive symptoms, sleep disturbance, physical activity, and goal disengagement.

DISCUSSION

Lower conscientiousness, optimism, and higher goal reengagement were linked with more severe perceived mental fatigability in older men. Personality traits may potentially contribute to early risk assessment for fatigability in later life. Future work should be longitudinal in nature and include personality assessments to confirm the temporality of the relationships observed.

Validation of the Traditional Chinese Version of the Pittsburgh Fatigability Scale for Older Adults

OBJECTIVES

The Pittsburgh Fatigability Scale (PFS) is a self-administered 10-item tool to measure physical and mental fatigability in older adults. The aim of the current study was to validate the psychometric properties of the traditional Chinese version of PFS (TC-PFS).

METHODS

We recruited 114 community-dwellingolder adults, where 35 were diagnosed with late-life depression (LLD), 26 with mild cognitive impairment (MCI), and 53 were cognitively normal (CN) from a larger community study of older adults. Statistical analyses were done separately for TC-PFS Physical and Mental subscales. Factor analysis was used for reliability, Cronbach's alpha for internal consistency, Pearson's correlation for construct validity, and group comparison for discriminative validity.

RESULTS

Factor analysis revealed a two-factor structure for both the TC-PFS Physical and Mental subscales with high reliability (α = 0.89 and 0.89, respectively). Patients with LLD had the highest PFS scores, with 80.0% and 82.9% classified as having greater physical and mental fatigability. For concurrent validity, we found moderate associations with the vitality and physical functioning subscales of the 36-Item Short Form Health Survey. For convergent validity, TC-PFS showed moderate association with emotional-related psychometrics, particularly for the Physical subscale in those with LLD. In contrast, TC-PFS Mental subscale showed correlations with cognitive function, particularly in the MCI group.

CONCLUSIONS

Our results indicate that the TC-PFS is a valid instrument to measure perceived physical and mental fatigability in older Taiwanese adults.Clinical implications: Perceived fatigability reflects the underlying physical, mental or cognitive function in older adults with or without depression.

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.

Perceived Physical Fatigability Predicts All-Cause Mortality in Older Adults

BACKGROUND

Perceived physical fatigability is highly prevalent in older adults and associated with mobility decline and other health consequences. We examined the prognostic value of perceived physical fatigability as an independent predictor of risk of death among older adults.

METHODS

Participants (N = 2,906), mean age 73.5 [SD, 10.4] years, 54.2% women, 99.7% white enrolled in the Long Life Family Study were assessed at Visit 2 (2014-2017) with 2.7 [SD, 1.0] years follow-up. The Pittsburgh Fatigability Scale (PFS), a 10-item, self-administered validated questionnaire (score range 0-50, higher=greater fatigability) measured perceived physical fatigability at Visit 2. Deaths post-Visit 2 through December 31, 2019 were identified by: family members notifying field centers, reporting during another family member's annual phone follow-up, an obituary, or Civil Registration System (Denmark). We censored all other participants at their last contact. Cox proportional hazard models predicted mortality by fatigability severity, adjusted for family relatedness and other covariates.

RESULTS

Age-adjusted PFS Physical scores were higher for those who died (19.1 [SE, 0.8]) compared to alive (12.2, [SE, 0.4]) overall, as well as across age strata (P<.001), except for those 60-69 years (P=.79). Participants with the most severe fatigability (PFS Physical scores ≥25) were over twice as likely to die (HR, 2.33 [95% CI, 1.65 to 3.28]) compared to those with less severe fatigability (PFS Physical scores <25) after adjustment.

CONCLUSIONS

This work underscores the utility of the PFS as a novel patient-reported prognostic indicator of phenotypic aging that captures both overt and underlying disease burden that predicts death.

Traits and treadmills: Association between personality and perceived fatigability in well-functioning community-dwelling older adults

Physical fatigability, or susceptibility to physical fatigue, is strongly associated with aging, disease, and disability. Over the lifecourse, personality traits are also connected to numerous age-related vulnerabilities and resistance-yet, their longitudinal association with fatigability remains unknown. Well-functioning community-dwelling volunteers aged ≥50 (N = 995) from the Baltimore Longitudinal Study of Aging (BLSA) were assessed over an average of 2 years on personality traits (NEO-PI-R; openness, conscientiousness, extraversion, agreeableness, and neuroticism) and perceived fatigability [Borg Rating of Perceived Exertion (RPE) after a 5-min slow treadmill walk; 6 (low) to 20 (high) exertion]. Linear and multinomial logistic regression models examined cross-sectional associations [treating fatigability continuously and by RPE category: low (6-7), intermediate (8-9), and high (10+)]. Generalized estimating equations (GEE) tested longitudinal associations. All models were adjusted for demographics and comorbid conditions. In cross-sectional models, openness, β = -.09 RPE (SE =.03); p < .01, conscientiousness, β = -.07 (.03); p < .05, and extraversion, β = -.10 (.03); p < .01, were negatively associated with fatigability. In parallel, lower openness, OR: .98, 95% CI [.96-1.00], conscientiousness, OR: .98, 95% CI [.96-1.00], and extraversion, OR: .97, 95% CI [.95-.99], corresponded with higher odds of having high versus low fatigability. In longitudinal models (mean follow-up time 2 ± 2 years), openness, conscientiousness, and extraversion associations remained significant and did not change over time (Trait × Year p values > .34). Together, findings suggest that personality plays a role in the perceived tolerance of fatigue in well-functioning older adults. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Evaluation of the Bidirectional Relations of Perceived Physical Fatigability and Physical Activity on Slower Gait Speed

BACKGROUND

Lower physical activity levels and greater fatigability contribute independently to slower gait speed in older adults. To fully understand the bidirectional relations between physical activity and fatigability, and to inform potential intervention strategies, we examined whether physical activity or fatigability explains more of the other factor's association on slower gait speed.

METHODS

Two generations (probands and offspring) of older adults (N = 2079, mean age 73.0 ± 10.0 years, 54.2% women, 99.7% White) enrolled in the Long Life Family Study were assessed at Visit 2 (2014-2017). Self-reported physical activity was measured with the Framingham Physical Activity Index and perceived physical fatigability using the Pittsburgh Fatigability Scale. Statistical mediation analyses were conducted separately by generation with linear mixed-effect models accounting for family relatedness and adjusted for demographics, health conditions, and field center.

RESULTS

Greater perceived physical fatigability explained the association of lower physical activity on slower gait speed via a 22.5% attenuation of the direct association (95% confidence interval [CI]: 15.0%-35.2%) for the probands and 39.5% (95% CI: 22.8%-62.6%) for the offspring. Whereas lower physical activity explained the association of greater perceived fatigability on slower gait speed via a 22.5% attenuation of the direct association (95% CI: 13.4%-32.8%) for the probands and 6.7% (95% CI: 3.8%-15.4%) for the offspring.

CONCLUSIONS

Our findings suggest that the impact of greater perceived physical fatigability on the association between lower physical activity and slower gait speed differs between younger-old and middle-to-oldest-old adults, indicating perceived physical fatigability as a potential mediator in the disablement pathway.

Slowing: A Vascular Geriatric Syndrome?

OBJECTIVES

This study aimed to investigate the interrelation between slowing in walking, thinking and mood, and their relationship with cerebral small vessel disease (CSVD) in a geriatric population.

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

566 geriatric outpatients from the Amsterdam Aging Cohort (49% female; age 79 ±6 years), who visited the Amsterdam UMC geriatric outpatient memory clinic.

METHODS

Patients underwent a comprehensive geriatric assessment, brain imaging, and a neuropsychological assessment as part of medical care. Three slowing aspects were investigated: gait speed, processing speed, and apathy symptoms (higher scores indicating more advanced slowing). We visually rated CSVD [white matter hyperintensities (WMHs), strategic lacunes, and microbleeds] on brain imaging.

RESULTS

Regression analyses showed that slowing in walking (gait speed) was associated with slowing in thinking [processing speed; β = 0.35, 95% confidence interval (CI) 0.22, 0.48] and slowing in mood (apathy symptoms; β = 0.21, 95% CI 0.13, 0.30), independent of important confounders. Large confluent areas of WMH (Fazekas 3) were associated with all slowing aspects: gait speed (β = 0.49, 95% CI 0.28, 0.71), processing speed (β = 0.36, 95% CI 0.19, 0.52) and apathy symptoms (β = 0.30, 95% CI 0.09, 0.51). In addition, in patients with more slowing aspects below predefined cutoffs, severe WMH was more common. Presence of ≥3 microbleeds was associated with apathy symptoms (β = 0.39, 95% CI 0.12, 0.66), whereas lacunes were not associated with slowing.

CONCLUSIONS AND IMPLICATIONS

This study provides evidence that slowing in walking, thinking, and mood are closely related and associated with CSVD. This phenotype or geriatric syndrome could be helpful to identify and characterize patients with CSVD.

Perceived physical fatigability improves after an exercise intervention among breast cancer survivors: a randomized clinical trial

BACKGROUND

Among breast cancer populations, exercise interventions resulted in positive but relatively small improvements on fatigue, which may be due to insensitive measures of global fatigue. Perceived fatigability-whole-body tiredness anchored to standardized tasks/activities of a specific intensity and duration-may help to detect effective exercise interventions reducing fatigue in oncology. We examined whether perceived physical fatigability improved after an exercise intervention.

METHODS

This single center randomized clinical trial of 49 breast cancer survivors was conducted from 2015 to 2017, among which 41 participants (22 = exercise, 19 = control) completed the trial and reported their perceived physical fatigability at the first (Visit 1) and the last visit (Visit 3) over 6-14 weeks. Perceived physical fatigability was measured using the 10-item, self-administered Pittsburgh Fatigability Scale (PFS) scored 0-50. The mean differences of perceived physical fatigability between Visit 3 and Visit 1 were computed and compared by intervention groups using two sample t test.

RESULTS

Among the 41 women in the study (mean age 54.9 ± 9.8 years; 80% white), sociodemographic, clinical characteristics and baseline fatigue level were similar by intervention groups, except for antiestrogen use. Post-intervention changes (mean ∆ ± SE) of PFS Physical scores were greater in the exercise group (- 4.4 ± 1.4; - 22.5%) than the control group (0.2 ± 1.4; + 1.0%) (p = .022).

CONCLUSION

The PFS captured a reduction in fatigue after the exercise intervention among breast cancer survivors. These findings aid mounting efforts to reduce fatigue in oncology by introducing a more sensitive instrument to measure perceived physical fatigability to better evaluate patient-reported outcomes in future cancer trials.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02770781.

Psychometric properties of the Korean version of the Pittsburgh Fatigability Scale in breast cancer survivors

BACKGROUND

Fatigability has recently emerged in oncology as a concept that anchors patients' perceptions of fatigue to defined activities of specified duration and intensity. This study aimed to examine the psychometric properties of the Korean version of the Pittsburgh Fatigability Scale (K-PFS) for women with breast cancer.

METHODS

This cross-sectional study involved 196 women with breast cancer recruited from a tertiary hospital in Seoul, Korea. Reliability was evaluated using Cronbach's alpha, and confirmatory factor analysis was conducted to examine the factor structure of the K-PFS. Four goodness-of-fit values were evaluated: (1) the comparative fit index (CFI), (2) the Tucker-Lewis index (TLI), (3) the root mean square error of approximation (RMSEA), and (4) the standardized root mean square residual (SRMR).

RESULTS

Of the 196 survivors, 71.1% had greater physical fatigability (K-PFS Physical score ≥ 15) and 52.6% had greater mental fatigability (K-PFS Mental score ≥ 13). The Cronbach's alpha coefficient for the total K-PFS scale was 0.926, and the coefficients for the physical and mental fatigability domains were 0.870 and 0.864, respectively. In the confirmatory factor analysis for physical fatigability, the SRMR value (0.076) supported goodness of fit, but other model fit statistics did not (CFI = 0.888, TLI = 0.826, and RMSEA = 0.224). For mental fatigability, although three goodness-of-fit values were acceptable (CFI = 0.948, TLI = 0.919, and SRMR = 0.057), the RMSEA value (0.149) did not indicate good model fit. However, each item coefficient was statistically significant (> 0.5), and the K-PFS was therefore found to be valid from a theoretical perspective.

CONCLUSION

This study provides meaningful information on the reliability and validity of the K-PFS instrument, which was developed to meet an important need in the context of breast cancer survivors. Additional research should examine its test-retest reliability and construct validity with performance measures.

Validation of perceived physical fatigability using the simplified-Chinese version of the Pittsburgh Fatigability Scale

BACKGROUND

The Pittsburgh Fatigability Scale (PFS) was developed to capture fatigue and demand in a single tool, filling a gap that no validated questionnaire existed to measure perceived fatigability. Since fatigability is a more sensitive measure of a person's susceptibility to fatigue, we validated the simplified-Chinese version of the PFS among Chinese community-dwelling older adults.

METHODS

This cross-sectional study was conducted in an urban community in Beijing between November 2018 and July 2019. The PFS was translated into simplified-Chinese by the translation, retro-translation method. Internal consistency of the Physical subscale of the PFS was evaluated by Cronbach's alpha. Convergent validity and discriminant validity were evaluated against physical performance measures (i.e., Short Physical Performance Battery & Timed Up and Go Test) and daily living performance (i.e., Barthel Index & Instrumental activity of daily living).

RESULTS

Our study included 457 participants, including 182 men (39.8%) and 275 women (60.2%). The age range of the included participants was 61-96 years (mean = 84.8 years, SD = 5.8 years). The simplified-Chinese version of PFS Physical scores showed strong internal consistency (Cronbach's alpha = 0.81). Higher PFS Physical scores were associated with worse physical performance, and daily living performance (|correlation coefficient| range: 0.36-0.56, p < .001). Age- and sex-adjusted PFS Physical scores had moderate to good overall discrimination for correctly classifying people by their physical performance and daily living performance (AUCs range 0.70-0.87, p < .001).

CONCLUSIONS

The PFS simplified-Chinese version is a valid instrument to assess perceived physical fatigability in Chinese-speaking older adults with good convergent validity. Thus, the PFS, with low cost and greater feasibility, is a desired tool to measure fatigability in large population studies.

Validation of Perceived Mental Fatigability Using the Pittsburgh Fatigability Scale

OBJECTIVES

Establish reliability, concurrent and convergent validity of the Pittsburgh Fatigability Scale (PFS) Mental subscale.

DESIGN

Cross-sectional.

SETTING

Older adults from two University of Pittsburgh registries, Baltimore Longitudinal Study of Aging (BLSA), and Long Life Family Study (LLFS).

PARTICIPANTS

PFS Mental subscale validation was conducted using three cohorts: (1) Development Sample (N = 664, 59.1% women, age 74.8 ± 6.4 years, PFS Mental scores 10.3 ± 9.1), (2) Validation Sample I-BLSA (N = 430, 51.9% women, age 74.5 ± 8.2 years, PFS Mental scores 9.4 ± 7.9), and (3) Validation Sample II-LLFS (N = 1,917, 54.5% women, age 72.2 ± 9.3 years, PFS Mental scores 7.5 ± 8.2).

MEASUREMENTS

Development Sample, Validation Sample I-BLSA, and Validation Sample II-LLFS participants self-administered the 10-item Pittsburgh Fatigability Scale. Validation Sample II-LLFS completed cognition measures (Trail Making Tests A and B), depressive symptomatology (Center for Epidemiologic Studies-Depression Scale, CES-D), and global fatigue from two CES-D items.

RESULTS

In the Development Sample and Validation Sample I-BLSA, confirmatory factor analysis showed all 10 items loaded on two factors: social and physical activities (fit indices: SRMSR = 0.064, RMSEA = 0.095, CFI = 0.91). PFS Mental scores had strong internal consistency (Cronbach's α = 0.85) and good test-retest reliability (ICC = 0.78). Validation Sample II-LLFS PFS Mental scores demonstrated moderate concurrent and construct validity using Pearson (r) or Spearman (ρ) correlations against measures of cognition (Trail Making Tests A (r = 0.14) and B (r = 0.17) time), depressive symptoms (r = 0.31), and global fatigue (ρ = 0.21). Additionally, the PFS Mental subscale had strong convergent validity, discriminating according to established clinical or cognitive testing cut points, with differences in PFS Mental scores ranging from 3.9 to 7.6 points (all P < .001). All analyses were adjusted for family relatedness, field center, age, sex, and education.

CONCLUSIONS

The validated PFS Mental subscale may be used in clinical and research settings as a sensitive, one-page self-administered tool of perceived mental fatigability in older adults.

Profiles of Accelerometry-Derived Physical Activity Are Related to Perceived Physical Fatigability in Older Adults

Physical activity (PA) is associated with greater fatigability in older adults; little is known about magnitude, shape, timing and variability of the entire 24-h rest–activity rhythm (RAR) associated with fatigability. We identified which features of the 24-h RAR pattern were independently and jointly associated with greater perceived physical fatigability (Pittsburgh Fatigability Scale, PFS, 0–50) in older adults (n = 181, 71.3 ± 6.7 years). RARs were characterized using anti-logistic extended cosine models and 4-h intervals of PA means and standard deviations across days. A K-means clustering algorithm approach identified four profiles of RAR features: “Less Active/Robust”, “Earlier Risers”, “More Active/Robust” and “Later RAR”. Quantile regression tested associations of each RAR feature/profile on median PFS adjusted for age, sex, race, body mass index and depression symptomatology. Later rise times (up mesor; β = 1.38, p = 0.01) and timing of midpoint of activity (acrophase; β = 1.29, p = 0.01) were associated with higher PFS scores. Lower PA between 4 a.m. and 8 a.m. was associated with higher PFS scores (β = −4.50, p = 0.03). “Less Active/Robust” (β = 6.14, p = 0.01) and “Later RAR” (β = 3.53, p = 0.01) patterns were associated with higher PFS scores compared to “Earlier Risers”. Greater physical fatigability in older adults was associated with dampened, more variable, and later RARs. This work can guide development of interventions aimed at modifying RARs to reduce fatigability in older adults.

Fatigability and Cardiorespiratory Impairments in Parkinson's Disease: Potential Non-Motor Barriers to Activity Performance

Parkinson's disease (PD) is the second most common neurodegenerative condition after Alzheimer's disease, affecting an estimated 160 per 100,000 people 65 years of age or older. Fatigue is a debilitating non-motor symptom frequently reported in PD, often manifesting prior to disease diagnosis, persisting over time, and negatively affecting quality of life. Fatigability, on the other hand, is distinct from fatigue and describes the magnitude or rate of change over time in the performance of activity (i.e., performance fatigability) and sensations regulating the integrity of the performer (i.e., perceived fatigability). While fatigability has been relatively understudied in PD as compared to fatigue, it has been hypothesized that the presence of elevated levels of fatigability in PD results from the interactions of homeostatic, psychological, and central factors. Evidence from exercise studies supports the premise that greater disturbances in metabolic homeostasis may underly elevated levels of fatigability in people with PD when engaging in physical activity. Cardiorespiratory impairments constraining oxygen delivery and utilization may contribute to the metabolic alterations and excessive fatigability experienced in individuals with PD. Cardiorespiratory fitness is often reduced in people with PD, likely due to the combined effects of biological aging and impairments specific to the disease. Decreases in oxygen delivery (e.g., reduced cardiac output and impaired blood pressure responses) and oxygen utilization (e.g., reduced skeletal muscle oxidative capacity) compromise skeletal muscle respiration, forcing increased reliance on anaerobic metabolism. Thus, the assessment of fatigability in people with PD may provide valuable information regarding the functional status of people with PD not obtained with measures of fatigue. Moreover, interventions that target cardiorespiratory fitness may improve fatigability, movement performance, and health outcomes in this patient population.