Impaired olfaction is associated with cognitive decline and neurodegeneration in the brain

Objective

We aimed to examine whether impaired olfaction is associated with cognitive decline and indicators of neurodegeneration in the brain of dementia-free older adults.

Methods

Within the Rush Memory and Aging Project, 380 dementia-free participants (mean age = 78 years) were followed for up to 15 years, and underwent MRI scans. Olfactory function was assessed using the Brief Smell Identification Test (B-SIT) at baseline, and categorized as anosmia (B-SIT <6), hyposmia (B-SIT 6–10 in men and 6–10.25 in women), and normal (B-SIT 10.25–12 in men and 10.5–12 in women). Cognitive function was annually assessed with a battery of 21 tests, from which composite scores were derived. Structural total and regional brain volumes were estimated. Data were analyzed using linear regression and mixed-effects models.

Results

At study entry, 138 (36.3%) had normal olfactory function, 213 (56.1%) had hyposmia, and 29 (7.6%) had anosmia. In multiadjusted mixed-effects models, hyposmia (β = −0.03, 95% confidence interval [CI] −0.05 to −0.02) and anosmia (β = −0.13, 95% CI −0.16 to −0.09) were associated with faster rate of cognitive decline compared to normal olfaction. On MRI, impaired olfaction (hyposmia or anosmia) was related to smaller volumes of the hippocampus (β = −0.19, 95% CI −0.33 to −0.05), and in the entorhinal (β = −0.16, 95% CI −0.24 to −0.08), fusiform (β = −0.45, 95% CI −0.78 to −0.14), and middle temporal (β = −0.38, 95% CI −0.72 to −0.01) cortices.

Conclusion

Impaired olfaction predicts faster cognitive decline and might indicate neurodegeneration in the brain among dementia-free older adults.

Associations Between Cardiovascular Risk, Structural Brain Changes, and Cognitive Decline

BACKGROUND

The impact of cardiovascular risk burden on cognitive trajectories and brain structure changes remains unclear.

OBJECTIVES

This study aimed to examine whether cardiovascular risk burden assessed by the Framingham General Cardiovascular Risk Score (FGCRS) is associated with cognitive decline and structural brain differences.

METHODS

Within the Rush Memory and Aging Project, 1,588 dementia-free participants (mean age: 79.5 years) were followed for up to 21 years. FGCRS was assessed at baseline and categorized into tertiles (lowest, middle, and highest). Episodic memory, semantic memory, working memory, visuospatial ability, and perceptual speed were assessed annually with a battery of 19 tests, from which composite scores were derived. A subsample (n = 378) of participants underwent magnetic resonance imaging. Structural total and regional brain volumes were estimated. Data were analyzed using linear mixed-effects models and linear regression models.

RESULTS

In all participants, FGCRS ranged from 4 to 28 (mean score: 15.6 ± 3.7). Compared with the lowest tertile of FGCRS, the highest tertile was associated with faster decline in global cognition (β = -0.019; 95% confidence interval [CI]: -0.035 to -0.003), episodic memory (β = -0.023; 95% CI: -0.041 to -0.004), working memory (β = -0.021; 95% CI: -0.035 to -0.007), and perceptual speed (β = -0.027; 95% CI: -0.042 to -0.011) over the follow-up. In magnetic resonance imaging data analyses, higher FGCRS was related to smaller volumes of the hippocampus (β = -0.021; 95% CI: -0.042 to -0.000), gray matter (β = -1.569; 95% CI: -2.757 to -0.382), and total brain (β = -1.588; 95% CI: -2.832 to -0.344), and greater volume of white matter hyperintensities (β = 0.035; 95% CI: 0.001 to 0.069).

CONCLUSIONS

Higher cardiovascular risk burden may predict decline in episodic memory, working memory, and perceptual speed and is associated with neurodegeneration and vascular lesions in the brain.

Association of Lifespan Cognitive Reserve Indicator With Dementia Risk in the Presence of Brain Pathologies

IMPORTANCE

Evidence on the association of lifespan cognitive reserve (CR) with dementia is limited, and the strength of this association in the presence of brain pathologies is unknown.

OBJECTIVE

To examine the association of lifespan CR with dementia risk, taking brain pathologies into account.

DESIGN, SETTING, AND PARTICIPANTS

This study used data from 2022 participants in the Rush Memory and Aging Project, an ongoing community-based cohort study with annual follow-up from 1997 to 2018 (mean follow-up, 6 years; maximum follow-up, 20 years). After excluding 420 individuals who had prevalent dementia, missing data on CR, or dropped out, 1602 dementia-free adults were identified at baseline and evaluated to detect incident dementia. During follow-up, 611 died and underwent autopsies. Data were analyzed from May to September 2018.

EXPOSURES

Information on CR factors (education; early-life, midlife, and late-life cognitive activities; and social activities in late life) was obtained at baseline. Based on these factors, lifespan CR scores were captured using a latent variable from a structural equation model and was divided into tertiles (lowest, middle, and highest).

MAIN OUTCOMES AND MEASURES

Dementia was diagnosed following international criteria. Neuropathologic evaluations for Alzheimer disease and other brain pathologies were performed in autopsied participants. The association of lifespan CR with dementia or brain pathologies was estimated using Cox regression models or logistic regression.

RESULTS

Of the 1602 included participants, 1216 (75.9%) were women, and the mean (SD) age was 79.6 (7.5) years. During follow-up, 386 participants developed dementia (24.1%), including 357 participants with Alzheimer disease-related dementia (22.3%). The multiadjusted hazards ratios (HRs) of dementia were 0.77 (95% CI, 0.59-0.99) for participants in the middle CR score tertile and 0.61 (95% CI, 0.47-0.81) for those in the highest CR score tertile compared with those in the lowest CR score tertile. In autopsied participants, CR was not associated with most brain pathologies, and the association of CR with dementia remained significant after additional adjustment for brain pathologies (HR, 0.60; 95% CI, 0.42-0.86). The highest CR score tertile was associated with a reduction in dementia risk, even among participants with high Alzheimer disease pathology (HR, 0.57; 95% CI, 0.37-0.87) and any gross infarcts (HR, 0.34; 95% CI, 0.18-0.62).

CONCLUSIONS AND RELEVANCE

High lifespan CR is associated with a reduction in dementia risk, even in the presence of high brain pathologies. Our findings highlight the importance of lifespan CR accumulation in dementia prevention.

Leisure activity and social integration mitigate the risk of dementia related to cardiometabolic diseases: A population-based longitudinal study

INTRODUCTION

The effect of comorbid cardiometabolic diseases (CMDs), including diabetes, heart diseases, and stroke, on dementia remains unclear.

METHODS

A cohort of 2648 dementia-free adults aged ≥60 years was followed up for 12 years. An active lifestyle was defined in accordance with the engagement in leisure activities and/or a social network. Cox models were used in data analysis.

RESULTS

The multiadjusted hazard ratio (HR, 95% confidence interval) of dementia was 1.41 (1.07-1.86) for one, 2.38 (1.58-3.59) for two, and 4.76 (2.04-11.13) for three CMDs. In joint exposure analysis, the HR of dementia was 3.36 (2.14-5.30) for participants with CMDs plus an inactive lifestyle and 1.32 (0.95-1.84) for those with CMDs plus an active lifestyle (reference: no CMDs plus active lifestyle). An active lifestyle delayed dementia onset by 3.50 years in people with CMDs.

DISCUSSION

CMDs, especially when comorbid, are associated with increased dementia risk; however, leisure activities and social integration mitigate this risk.

Association of lifespan cognitive reserve indicator with the risk of mild cognitive impairment and its progression to dementia

INTRODUCTION

The association of lifespan cognitive reserve (CR) with mild cognitive impairment (MCI) remains controversial. We aimed to examine the association of lifespan CR indicator with the risk of MCI and its progression to dementia, taking brain pathologies into account.

METHODS

In a community-based cohort study (mean age, 79 years) with annual follow-up (median, 5.16 years; maximum, 20 years), a cognitively intact group (n = 1182) and an MCI group (n = 420) were identified at baseline. During the follow-up, 611 participants died and underwent autopsies. CR indicator encompassing education, early life to late-life cognitive and social activities were obtained and tertiled.

RESULTS

The multi-adjusted hazard ratio (HR) of MCI was 0.72 (95% confidence interval [CI] 0.58 to 0.90) in the cognitively intact group, and the HR of dementia was 0.66 (95% CI 0.45 to 0.97) in the MCI group for participants with the highest CR indicator (reference: the lowest CR indicator). Among MCI participants with brain pathologies, dementia incidence was about 50% lower in people with the highest CR indicator than the lowest CR indicator.

DISCUSSION

High lifespan CR indicator reduces risk of MCI, and delays its progression to dementia.

Dementia Risk and Disadvantaged Neighborhoods

Importance

Residence in a disadvantaged neighborhood may be associated with an increased risk for cognitive impairment and dementia but is understudied in nationally representative populations.

Objective

To investigate the association between the Area Deprivation Index (ADI) and dementia.

Design, Setting, and Participants

Retrospective cohort study within the US Veterans Health Administration from October 1, 1999, to September 30, 2021, with a national cohort of older veterans receiving care in the largest integrated health care system in the United States. For each fiscal year, a 5% random sample was selected from all patients (n = 2 398 659). Patients with missing ADI information (n = 492 721) or missing sex information (n = 6) and prevalent dementia cases (n = 25 379) were excluded. Participants had to have at least 1 follow-up visit (n = 1 662 863). The final analytic sample was 1 637 484.

Exposure

Neighborhoods were characterized with the ADI, which combines several sociodemographic indicators (eg, income, education, employment, and housing) into a census block group-level index of disadvantage. Participants were categorized into ADI rank quintiles by their census block group of residence (higher ADI rank quintile corresponds with more deprivation).

Main Outcome and Measures

Time to dementia diagnosis (using International Classification of Diseases, Ninth Revision and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes) was estimated with Cox proportional hazards models with age as the time scale, and the sensitivity of the findings was evaluated with Fine-Gray proportional hazards models, accounting for competing risk of death.

Results

Among the 1 637 484 Veterans Health Administration patients, the mean (SD) age was 68.6 (7.7) years, and 1 604 677 (98.0%) were men. A total of 7318 patients were Asian (0.4%), 151 818 (9.3%) were Black, 10 591 were Hispanic (0.6%), 1 422 713 (86.9%) were White, and 45 044 (2.8%) were of other or unknown race and ethnicity. During a mean (SD) follow-up of 11.0 (4.8) years, 12.8% of veterans developed dementia. Compared with veterans in the least disadvantaged neighborhood quintile, those in greater disadvantage groups had an increased risk of dementia in models adjusted for sex, race and ethnicity, and psychiatric and medical comorbid conditions (first quintile = reference; second quintile adjusted hazard ratio [HR], 1.09 [95% CI, 1.07-1.10]; third quintile adjusted HR, 1.14 [95% CI, 1.12-1.15]; fourth quintile adjusted HR, 1.16 [95% CI, 1.14-1.18]; and fifth quintile adjusted HR, 1.22 [95% CI, 1.21-1.24]). Repeating the main analysis using competing risk for mortality led to similar results.

Conclusions and Relevance

Results of this study suggest that residence within more disadvantaged neighborhoods was associated with higher risk of dementia among older veterans integrated in a national health care system.

Epidemiology and Risk Factors for Dementia

In this article, the authors discuss primarily what is known about the epidemiology of all-cause dementia. Dementia is caused by a complex interplay of genetics, comorbidities, and lifestyle factors, and drug development has been challenging. However, evidence from large, prospective, observational studies has identified a variety of factors that may prevent or delay the onset of dementia. Several of these factors are modifiable and lend themselves to well to treatments currently available. The authors discuss the state of current evidence on dementia risk factors, the most promising avenues, and future directions for dementia prevention and management.

The Metabolic Syndrome Is Associated With Lower Cognitive Performance and Reduced White Matter Integrity in Midlife: The CARDIA Study

Background

Cardiovascular disease risk factors play a critical role in brain aging. The metabolic syndrome (MetS), a constellation of cardiovascular risk factors, has been associated with poorer cognition in old age; however, it is unclear if it is connected to brain health earlier in life.

Methods

We investigated the association of MetS (n = 534, 18.5%) vs. no MetS (n = 2,346, 81.5%) with cognition in midlife within the prospective study, Coronary Artery Risk Development in Young Adults (CARDIA). At midlife (mean age 50), MetS was defined using National Cholesterol Education Program guidelines. At the 5-year follow-up, a cognitive battery was administered including tests of processing speed (Digit Symbol Substitution Test, DSST), executive function (the Stroop Test), verbal memory (Rey Auditory Verbal Learning Test, RAVLT), verbal fluency (category and letter fluency), and global cognitive function (Montreal Cognitive Assessment, MoCA). A sub-sample (n = 453) underwent brain MRI.

Results

Participants with MetS had worse performance on tests of verbal fluency, processing speed, executive function, and verbal memory (p < 0.05), but not on global cognition. MetS was also associated with lower frontal, parietal, temporal, and total white matter integrity (p < 0.05), as assessed with fractional anisotropy.

Conclusions

MetS is associated with lower cognition and microstructural brain alterations already at midlife, suggesting that MetS should be targeted earlier in life in order to prevent adverse brain and cognitive outcomes.

The relation of poor mastication with cognition and dementia risk: a population-based longitudinal study

We investigated the effect of poor masticatory ability on cognitive trajectories and dementia risk in older adults. 544 cognitively intact adults aged ≥50 were followed for up to 22 years. Cognitive domains (verbal, spatial/fluid, memory, and perceptual speed) were assessed at baseline and follow-ups. Dementia was ascertained according to standard criteria. Masticatory ability was assessed using the Eichner Index and categorized according to the number of posterior occlusal zones: A (all four), B (3-1), and C (none).

At baseline, 147 (27.0%) participants were in Eichner category A, 169 (31.1%) in B and 228 (41.9%) in C. After the age of 65, participants in Eichner category B and C showed an accelerated decline in spatial/fluid abilities (β: -0.16, 95% CI: -0.30 to -0.03) and (β: -0.15, 95% CI: -0.28 to -0.02), respectively. Over the follow-up, 52 incident dementia cases were identified. Eichner categories B or C were not associated with an increased risk of dementia, compared to category A (Hazard Ratio [HR]: 0.83, 95% CI: 0.39 to 1.76 and HR: 0.63, 95% CI: 0.30 to 1.29, respectively).

Poor masticatory ability is associated with an accelerated cognitive decline in fluid/spatial abilities, however it was not related to a higher risk of dementia.

The Role of Cognitive Impairment, Physical Disability, and Chronic Conditions in the Association of Sleep Duration With All-Cause Mortality Among Very Old Adults

OBJECTIVE

This study aimed to examine the relationship between sleep duration and all-cause mortality, and to assess the role of cognitive impairment, physical disability, and chronic conditions on this association among very old adults.

DESIGN

A prospective cohort study.

SETTING AND PARTICIPANTS

Within the Chinese Longitudinal Healthy Longevity Surveys, 17,637 oldest-old aged 80-105 years were followed up to 10 years (2005- 2014).

MEASURES

Data on sleep duration at baseline were based on self-report and were categorized as short (<7 hour), moderate (7-9 hours), and long sleep (>9 hours). Information on cognitive function using the Mini-Mental State Examination (MMSE), physical disability using Activities of Daily Living (ADL), and chronic conditions including diabetes, heart disease, stroke, asthma, and cancer were collected at baseline based on a structured questionnaire. Information about vital status was ascertained and confirmed by a close family member or village doctor of the participant during the follow-up. Data were analyzed using Cox proportional hazards models, with adjustment for potential confounders.

RESULTS

During the follow-up of 10 years, 11,067 (62.7%) participants died. The multivariate-adjusted hazard ratios (HRs) with 95% confidence interval (CI) for mortality were 1.03 (0.98-1.09) for short sleep and 1.13 (1.08-1.18) for long sleep compared with moderate sleep duration. In stratified analysis by cognitive impairment, physical disability, and chronic conditions, the risk of morality was present only among people with MMSE scores ≤24 but did not differ much when stratified by physical disability and chronic conditions. There was a statistically significant interaction between long sleep and cognitive impairment on mortality (P for interaction = .002).

CONCLUSIONS AND IMPLICATIONS

Long sleep duration is associated with higher risk of mortality in very old adults independently of health conditions. Cognitive impairment may enhance this association. These findings suggest that health practitioners and families should be aware of the potential adverse prognosis associated with long sleep.

Loneliness, Not Social Support, Is Associated with Cognitive Decline and Dementia Across Two Longitudinal Population-Based Cohorts

Background:

Poor social health is likely associated with cognitive decline and risk of dementia; however, studies show inconsistent results. Additionally, few studies separate social health components or control for mental health.

Objective:

To investigate whether loneliness and social support are independently associated with cognitive decline and risk of dementia, and whether depressive symptoms confound the association.

Methods:

We included 4,514 participants from the population-based Rotterdam Study (RS; aged 71±7SD years) followed up to 14 years (median 10.8, interquartile range 7.4–11.6), and 2,112 participants from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K; aged 72±10SD years) followed up to 10 years (mean 5.9±1.6SD). At baseline, participants were free of major depression and scored on the Mini-Mental State Examination (MMSE) ≥26 for RS and ≥25 for SNAC-K. We investigated loneliness, perceived social support, and structural social support (specifically marital status and number of children). In both cohorts, dementia was diagnosed and cognitive function was repeatedly assessed with MMSE and a global cognitive factor (g-factor).

Results:

Loneliness was prospectively associated with a decline in the MMSE in both cohorts. Consistently, persons who were lonely had an increased risk of developing dementia (RS: HR 1.34, 95%CI 1.08–1.67; SNAC-K: HR 2.16, 95%CI 1.12–4.17). Adjustment for depressive symptoms and exclusion of the first 5 years of follow-up did not alter results. Neither perceived or structural social support was associated with cognitive decline or dementia risk.

Conclusion:

Loneliness, not social support, predicted cognitive decline and incident dementia independently of depressive symptoms.

Long-term depressive symptoms and midlife brain age

BACKGROUND

Evidence suggests that depression may be a risk factor for dementia in older adults, but the link between depressive symptoms and brain health earlier in life is less understood. Our aim was to investigate the association between long-term depressive symptoms in young to mid-adulthood and a measure of brain age derived from structural MRI.

METHODS

From the Coronary Artery Risk Development in Young Adults study, we identified 649 participants (age 23-36 at baseline) with brain MRI and cognitive testing. Long-term depressive symptoms were measured with the Center for Epidemiological Studies Depression scale (CESD) six times across 25 years and analyzed as time-weighted averages (TWA). Brain age was derived using previously validated high dimensional neuroimaging pattern analysis, quantifying individual differences in age-related atrophy. Elevated depressive symptoms were defined as CES-D ≥16. Linear regression was used to test the association between TWA depressive symptoms, brain aging, and cognition.

RESULTS

Each standard deviation (5-points) increment in TWA depression symptoms over 25 years was associated with one-year greater brain age (β: 1.14, 95 % confidence interval [CI]: 0.57 to 1.71). Participants with elevated TWA depressive symptoms had on average a 3-year greater brain age (β: 2.75, 95 % CI: 0.43 to 5.08). Moreover, elevated depressive symptoms were associated with higher odds of poor cognitive function in midlife (OR: 3.30, 95 % CI: 1.37 to 7.97).

LIMITATIONS

Brain age was assessed at one time, limiting our ability to evaluate the temporality of depressive symptoms and brain aging.

CONCLUSIONS

Elevated depressive symptoms in early adulthood may have implications for brain health as early as in midlife.

Shared risk and protective factors between Alzheimer's disease and ischemic stroke: A population-based longitudinal study

INTRODUCTION

Stroke, especially ischemic stroke's (IS) link with Alzheimer's disease (AD) remains unclear.

METHODS

This prospective cohort study included 2459 AD- and cerebrovascular disease-free older adults at baseline (mean age 71.9 ± 10.3 years, Stockholm, Sweden). Using Cox regressions, shared risk factors (SRFs) and shared protective factors (SPFs) between AD and IS were recognized when their hazard ratios in both AD and IS models were significant and in the same direction.

RESULTS

During the follow-up period of up to 15 years, 132 AD and 260 IS mutually exclusive cases were identified. SRFs were low education, sedentary lifestyle, and heart diseases. High levels of psychological well-being, actively engaging in leisure activities, and a rich social network were SPFs. Having ≥1 SPF reduced 47% of AD and 28% of IS risk among people with a low risk profile (<2 SRFs), and 38% of AD and 31% of IS risk with a high risk profile (≥2 SRFs). In total, 57.8% of AD/IS cases could be prevented if individuals have ≥1 SPF and no SRF.

DISCUSSION

AD and IS share risk/protective profiles, and SPFs seem to counteract the adverse effects of SRFs on both AD and IS.

Joint trajectories of episodic memory and odor identification in older adults: patterns and predictors

Emerging evidence suggests that olfactory function is closely linked to memory function. The aims of this study were to assess whether olfactory and episodic memory functions follow similar age-related decline trajectories, to identify different patterns of decline, as well as predictors of the patterns. 1023 participants from the Memory and Aging Project were followed for up to 8 years with annual episodic memory and odor identification assessments. Trajectories were modelled using growth mixture models. Multivariate logistic regression was used to identify pattern predictors. Three patterns of joint trajectories were identified; Class 1- stable average performance in both functions (n=690, 67.4%); Class 2- stable average episodic memory and declining odor identification (n=231, 22.6%); and Class 3- decline in both functions (n= 102, 10.0%). Class predictors included age, sex, APOE ε4 status, cognitive activity level and BMI. Participants in Class 3 were most likely to develop dementia. Episodic memory and olfactory function show similar trajectories in aging. Such classification can contribute to a better understanding of the factors related to cognitive decline and dementia.

Association Between Sensory Impairment and Dementia: The Roles of Social Network and Leisure Activity

BACKGROUND

Evidence suggests that sensory impairment is linked to dementia; however, the role of social network and leisure activity in this relationship is unclear.

OBJECTIVE

Examine the association of hearing and visual impairment with dementia, and whether a rich social network and leisure activity moderates this association.

METHODS

Dementia-free older adults from the Swedish National Study on Aging and Care in Kungsholmen (n = 2,579) were followed up for up for a median of 10 years (interquartile range = 6). Visual impairment was assessed with a reading acuity test, and hearing impairment was ascertained via self-report and medical records. Dementia was diagnosed following international criteria. Data on social network and leisure activity was collected via self-report. Hazard ratios (HRs) of dementia risk were derived from Cox regression models.

RESULTS

Dual impairment, but not single impairment in hearing and vision was associated with a higher risk of dementia (HR: 1.62, 95% CI: 1.16 to 2.27). Compared to participants with no sensory impairment and a moderate-to-rich social network, those with dual impairment and low social network or leisure activity had higher dementia risk (HR: 2.08, 95% CI: 1.43 to 3.22; HR: 2.08, 95% CI: 1.43 to 3.22, respectively), whereas participants with dual impairment with a moderate-to-rich social network or leisure activity did not have significantly higher dementia risk (HR; 1.42, 95% CI: 0.87 to 2.33; HR; 1.42, 95% CI: 0.87 to 2.33, respectively).

CONCLUSION

A richer social network and participation in stimulating activities may mitigate the higher dementia risk in older adults with dual impairment in vision and hearing.

Association of Self-Reported Sleep Characteristics With Neuroimaging Markers of Brain Aging Years Later in Middle-Aged Adults

OBJECTIVES

To determine the association between early midlife sleep and advanced brain aging patterns in late midlife.

METHODS

Using the CARDIA study, we analyzed sleep data at baseline and 5 years later, focusing on short sleep duration, bad sleep quality (SQ), difficulty initiating and maintaining sleep (DIS and DMS), early morning awakening (EMA), and daytime sleepiness. These were categorized into 0-1, 2-3, and >3 poor sleep characteristics (PSC). Brain MRIs obtained 15 years later were used to determine brain age through a machine learning approach based on age-related atrophy.

RESULTS

This cohort study included 589 participants (mean age 40.4 ± 3.4 years, 53% women). At baseline, around 70% reported 0-1 PSC, 22% reported 2%-3%, and 8% reported >3 PSC. In multivariable linear regression analyses, participants with 2-3 or >3 PSC had 1.6-year (β = 1.61, 95% CI 0.28-2.93) and 2.6-year (β = 2.64, 95% CI 0.59-4.69) older brain age, respectively, compared with those with 0-1 PSC. Of the individual characteristics, bad SQ, DIS, DMS, and EMA were associated with greater brain age, especially when persistent over the 5-year follow-up.

DISCUSSION

Poor sleep was associated with advanced brain age in midlife, highlighting the importance of investigating early sleep interventions for preserving brain health.

The Association Between Cognitive Reserve and Cognitive Trajectories Among Older Adults

Background and Objectives

Prior studies on cognitive reserve (CR) and cognitive trajectories are limited and have had conflicting results. Furthermore, most studies have used a single measure of CR that may not reflect a comprehensive exposure. The objective of this study is to determine the impact of individual and composite CR measures on cognitive decline over a 6-year period.

Research Design and Methods

We studied 55,340 participants from 16 European countries, aged 50 and older, who participated in the Survey of Health, Aging, and Retirement in Europe. We used cognitive measures (including immediate memory, delayed memory, verbal fluency, and numeracy) and 3 CR factors (education, occupation, and cognitive activities) collected in 4 waves from 2011 to 2017. Structural equation modeling was used to construct the composite CR score, analyzed as tertile. Linear mixed-effect models were used to examine the study aims.

Results

At baseline, the highest composite CR tertile was associated with a higher cognition score than the middle and lowest CR tertiles (β: -0.28, 95% confidence interval [CI]: -0.29 to -0.26; β: -0.71, 95% CI: -0.72 to -0.70, respectively), as well as for all individual cognitive domains. At longitudinal results, compared with the lowest CR, the highest but not the middle CR tertile demonstrated a slower 6-year decline in global cognition (β: -0.02, 95 % CI: -0.03 to -0.01), as well as in all cognitive domains (p < .05).

Discussion and Implications

A composite CR could be a protective factor for cognitive performance and cognitive decline, and it is more sensitive and inclusive than an individual CR indicator alone.

Cardiovascular-kidney-metabolic syndrome and incidence of dementia among older adults

BACKGROUND

Cardiovascular-Kidney-Metabolic Syndrome (CKM) has profound impacts on cardiovascular events and mortality, yet its association with dementia risk remains poorly understood.

OBJECTIVES

To investigate associations between CKM and dementia risk.

DESIGN

The prospective cohort study is within the Health, Aging, and Body Composition study, which enrolled participants from 1997 to 1998, with a 15-year follow-up for incident dementia.

SETTING

The population-based study took place in two US communities in Memphis, Tennessee, and Pittsburgh, Pennsylvania.

PARTICIPANTS

Of the 3,075 participants aged 70 to 79 years initially enrolled, 14 were excluded for lacking baseline cognitive assessment, 308 for baseline cognitive impairment, 4 for missing follow-up, and 108 for missing CKM data, resulting in 2,641 in the analysis.

MEASUREMENTS

CKM staging, as defined recently by the American Heart Association framework, was based on constructs comprising dysfunctional adiposity, metabolic risk factors, chronic kidney disease (CKD), and cardiovascular disease (CVD). Dementia was identified using hospital records, prescriptions for dementia medication, and a test of global cognition. Adjusted Cox and Fine-Gray proportional hazards models were used to estimate dementia risk and account for competing risk of death.

RESULTS

The 2,641 participants had a mean (SD) age of 74 (2.8) years at baseline; 53 % were female, 36 % were of Black race, and had a range of baseline CKM: 3 % Stage 0 (no CKM), 4 % Stage 1 (excess/dysfunctional adiposity), 26 % Stage 2 (metabolic risk factors), 24 % Stage 3 (subclinical CVD and CKD), and 43 % Stage 4 (clinical CVD and CKD). Compared to participants with CKM Stages 0-2, those with CKM Stages 3-4 had a 50 % increase in dementia risk (hazard ratio 1.50, 95 % CI 1.20 to 1.86) in the fully adjusted model. The association remained significant after additional adjustment for metabolic risk factors, CVD, and CKD, both separately and together. Accounting for competing risk of death yielded similar results.

CONCLUSIONS

Among community-dwelling older adults, advanced CKM is associated with an increased risk of dementia. Older adults with CKM may need to be followed closely for adverse cognitive outcomes, and modifiable risk factors should be managed proactively.