The Importance of Racially and Ethnically Inclusive Gait Speed Reference Values in Individuals 90 Years and Older: LifeAfter90.

BACKGROUND AND PURPOSE: Clinicians use reference values to contextualize physical performance scores, but data are sparse in individuals 90 years and older and racial/ethnic diversity is limited in existing studies. Gait speed provides valuable information about an individual's health status. Slow gait speed is associated with falls, cognitive decline, and mortality. Here, we report gait speed reference values in a racially/ethnically diverse oldest-old cohort. METHODS: LifeAfter90 is a multiethnic cohort study of individuals 90 years and older. Participants are long-term members of an integrated healthcare delivery system without a dementia diagnosis at enrollment. We assessed gait speed using the 4-m walk test and calculated means, standard deviations, and percentiles by age, sex, assistive device use, and device type. We used linear regression to compare means by sex, age, device use and type, living situation and arrangement, and race/ethnicity. RESULTS AND DISCUSSION: The mean age of the 502 participants was 92.9 (range 90.1-102.8) years. Of these, 62.6% were women, 34.7% were college educated, 90.8% lived in a private residence, 20.9% self-reported as Asian, 22.5% as Black, 11.8% as Hispanic, 35.7% as White, and 9.2% as multiple, "other," or declined to state. The overall mean gait speed was 0.54 m/s (women = 0.51 m/s, men = 0.58 m/s). Mean gait speeds were 0.58 m/s, 0.53 m/s, and 0.48 m/s in the 90 to 91, 92 to 93, and 94+ age categories, respectively. In those without a device, mean gait speed was 0.63 m/s compared to 0.40 m/s in those with a device (cane = 0.44 m/s, walker = 0.37 m/s). Mean gait speed was significantly slower in women compared to men, age category 94+ compared to 90 to 91, participants with a device compared to those without, participants with a walker compared to a cane, and Black participants compared to Asian and White participants. However, differences by race/ethnicity were attenuated when chronic health conditions were considered. CONCLUSIONS: Reference values developed from this multiethnic 90+ cohort will help clinicians interpret gait speed measures and tailor recommendations toward a 90+ population that is growing in number and in racial/ethnic diversity.

DXA-Measured Abdominal Adipose Depots and Structural Brain Integrity in Postmenopausal Women.

BACKGROUND: This study extends prior research from the MRI substudy of the Women's Health Initiative Memory Study (WHIMS-MRI) linking BMI to reduced brain atrophy and ischemic lesion load by examining DXA-based measurements of total body fat, total abdominal adipose tissue (TAT), abdominal visceral (VAT) and subcutaneous (SAT) adipose tissue, gynoid fat, and overall leg fat. METHODS: The analytic sample consisted of 61 postmenopausal women (baseline mean age 69.5 [3.6]) enrolled in WHIMS-MRI who had undergone DXA scans. DXA scans were completed at years 0, 3, and 6, and MRI scans were conducted ~8 years after baseline. Adjusted linear regression models were used to analyze the association between adiposity averaged across the 3-time points and volumes of brain regions previously linked to dementia. RESULTS: Higher levels of total body fat, TAT, VAT, SAT, gynoid, and overall leg fat were associated with larger hippocampal volume (ß 0.02 [95% CI, 0.004-0.04]; 0.11 [0.02-0.21]; 0.26 [0.04-0.47]; 0.18 [0.03-0.33]; 0.18 [0.05-0.30]; 0.07 [0.009-0.12], respectively). No other significant associations were observed. CONCLUSION: Higher levels of adiposity were positively associated with hippocampal volume. Additional research with larger sample sizes is needed to ascertain the significance of this association.

Associations of Amyloid Burden, White Matter Hyperintensities, and Hippocampal Volume With Cognitive Trajectories in the 90+ Study.

BACKGROUND AND OBJECTIVES: Amyloid pathology, vascular disease pathology, and pathologies affecting the medial temporal lobe are associated with cognitive trajectories in older adults. However, only limited evidence exists on how these pathologies influence cognition in the oldest old. We evaluated whether amyloid burden, white matter hyperintensity (WMH) volume, and hippocampal volume (HV) are associated with cognitive level and decline in the oldest old. METHODS: This was a longitudinal, observational community-based cohort study. We included participants with 18F-florbetapir PET and MRI data from the 90+ Study. Amyloid load was measured using the standardized uptake value ratio in the precuneus/posterior cingulate with eroded white matter mask as reference. WMH volume was log-transformed. All imaging measures were standardized using sample means and SDs. HV and log-WMH volume were normalized by total intracranial volume using the residual approach. Global cognitive performance was measured by the Mini-Mental State Examination (MMSE) and modified MMSE (3MS) tests, repeated every 6 months. We used linear mixed-effects models with random intercepts; random slopes; and interaction between time, time squared, and imaging variables to estimate the associations of imaging variables with cognitive level and cognitive decline. Models were adjusted for demographics, APOE genotype, and health behaviors. RESULTS: The sample included 192 participants. The mean age was 92.9 years, 125 (65.1%) were female, 71 (37.0%) achieved a degree beyond college, and the median follow-up time was 3.0 years. A higher amyloid load was associated with a lower cognitive level (ßMMSE = -0.82, 95% CI -1.17 to -0.46; ß3MS = -2.77, 95% CI -3.69 to -1.84). A 1-SD decrease in HV was associated with a 0.70-point decrease in the MMSE score (95% CI -1.14 to -0.27) and a 2.27-point decrease in the 3MS score (95% CI -3.40 to -1.14). Clear nonlinear cognitive trajectories were detected. A higher amyloid burden and smaller HV were associated with faster cognitive decline. WMH volume was not significantly associated with cognitive level or decline. DISCUSSION: Amyloid burden and hippocampal atrophy are associated with both cognitive level and cognitive decline in the oldest old. Our findings shed light on how different pathologies contributed to driving cognitive function in the oldest old.

Resilience to AD pathology in Top Cognitive Performers.

Successful cognitive aging is often thought to result from resistance to the accumulation of pathology, resilience to the effects of pathological accumulation, or some combination of the two. While evidence for resilience has been found in typical aging populations, the oldest-old provide us with a unique window into the role of pathological accumulation in impacting cognition. Here, we aimed to assess group differences in measures of amyloid and tau across older age groups using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI age: 60-89) and The 90+ Study (age: 90-101). Additionally, using the ADNI dataset, we performed exploratory analyses of regional cingulate AV-45 SUVRs to assess if amyloid load in particular areas was associated with Top Cognitive Performance (TCP). Consistent with the literature, results showed no group differences in amyloid SUVRs both regionally and in the whole cortex. For tau with AV-1451, we also observed no differences in Braak composite SUVRs. Interestingly, these relationships persisted in the oldest-old. This indicates that Top Cognitive Performance throughout aging does not reflect resistance to amyloid and tau burden, but that other mechanisms may be associated with protection against amyloid and tau related neurodegeneration.

Comprehensive assessment of TDP-43 neuropathology data in the National Alzheimer's Coordinating Center database.

TDP-43 proteinopathy is a salient neuropathologic feature in a subset of frontotemporal lobar degeneration (FTLD-TDP), in amyotrophic lateral sclerosis (ALS-TDP), and in limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC), and is associated with hippocampal sclerosis of aging (HS-A). We examined TDP-43-related pathology data in the National Alzheimer's Coordinating Center (NACC) in two parts: (I) availability of assessments, and (II) associations with clinical diagnoses and other neuropathologies in those with all TDP-43 measures available. Part I: Of 4326 participants with neuropathology data collected using forms that included TDP-43 assessments, data availability was highest for HS-A (97%) and ALS (94%), followed by FTLD-TDP (83%). Regional TDP-43 pathologic assessment was available for 77% of participants, with hippocampus the most common region. Availability for the TDP-43-related measures increased over time, and was higher in centers with high proportions of participants with clinical FTLD. Part II: In 2142 participants with all TDP-43-related assessments available, 27% of participants had LATE-NC, whereas ALS-TDP or FTLD-TDP (ALS/FTLD-TDP) was present in 9% of participants, and 2% of participants had TDP-43 related to other pathologies ("Other TDP-43"). HS-A was present in 14% of participants, of whom 55% had LATE-NC, 20% ASL/FTLD-TDP, 3% Other TDP-43, and 23% no TDP-43. LATE-NC, ALS/FTLD-TDP, and Other TDP-43, were each associated with higher odds of dementia, HS-A, and hippocampal atrophy, compared to those without TDP-43 pathology. LATE-NC was associated with higher odds for Alzheimer's disease (AD) clinical diagnosis, AD neuropathologic change (ADNC), Lewy bodies, arteriolosclerosis, and cortical atrophy. ALS/FTLD-TDP was associated with higher odds of clinical diagnoses of primary progressive aphasia and behavioral-variant frontotemporal dementia, and cortical/frontotemporal lobar atrophy. When using NACC data for TDP-43-related analyses, researchers should carefully consider the incomplete availability of the different regional TDP-43 assessments, the high frequency of participants with ALS/FTLD-TDP, and the presence of other forms of TDP-43 pathology.

The Relationship between All-Cause Dementia and Acute Diabetes Complications among American Indian and Alaska Native Peoples.

BACKGROUND: American Indian and Alaska Native people (AI/AN) bear a disproportionate burden of diabetes. Growing evidence shows significant associations between several acute diabetes complications and dementia among diabetes patients. However, little is known about these relationships among AI/AN adults. Here, we aim to investigate these associations among AI/AN adults. METHODS: This cross-sectional study extracted data from the Indian Health Service's (IHS) National Data Warehouse and related administrative databases. A total of 29,337 IHS actual users with diabetes who were 45+ years old during fiscal year 2013 were included. All-cause dementia and diabetes complications were identified using ICD-9 diagnostic codes. Negative binomial regression models were used to evaluate the associations of interest. RESULTS: Nearly 3% of AI/AN diabetes patients had a dementia diagnosis. After controlling for covariates, dementia was associated with a 94% higher rate of severe hypoglycemia (Incidence Rate Ratio [IRR = 1.94, 95% CI:1.50-2.51), 52% higher rate of severe hyperglycemia (IRR = 1.52, 95% CI, 1.11-2.08), and 92% higher rate of any acute complication (IRR = 1.92, 95% CI:1.53-2.41). CONCLUSIONS: AI/AN diabetes patients with dementia suffered from considerably higher rates of acute diabetes complications than their counterparts without dementia. The clinical management of patients with comorbid diabetes and dementia is particularly challenging and may require individualized treatment approaches.

Neuropathologic changes at age 90+ related to sleep duration 19 to 40 years earlier: The 90+ Study.

INTRODUCTION: We investigated the association between sleep duration and neuropathologic changes 19 to 40 years later in oldest-old (age 90+) participants of The 90+ Study. METHODS: Participants self-reported sleep duration and underwent neuropathologic evaluation. We categorized sleep duration as < 7, 7 to 8 = reference, > 8 hours and dichotomized neuropathologic changes as present/absent. We estimated odds ratio (OR) and 95% confidence intervals (CI) using logistic regression. RESULTS: In 264 participants, mean age at sleep self-report was 69 years, mean age at autopsy was 98 years, and mean interval between sleep self-report and autopsy was 29 years (range: 19-40). Those reporting > 8 hours of sleep had lower likelihood of limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) inclusions (OR = 0.18; CI = 0.04-0.82) and amyloid beta deposits (OR = 0.34; 95% CI = 0.12-0.94). DISCUSSION: Long self-reported sleep is associated with lower odds of neurodegenerative neuropathologic changes 19 to 40 years later in the oldest-old, suggesting a potential role of sleep in accumulation of dementia-related neuropathologies. HIGHLIGHTS: Association of self-reported sleep with non-Alzheimer's disease neuropathologic changes has not been explored. Whether sleep duration is related to dementia neuropathologic changes decades later is unclear. Long self-reported sleep is associated with lower odds of Alzheimer's disease neuropathologic change 19 to 40 years later in the oldest-old. Long self-reported sleep is associated with lower odds of limbic-predominant age-related TDP-43 encephalopathy neuropathologic change 19 to 40 years later in the oldest-old.

Potential Effects of Long-Term Exposure to Air Pollution on Dementia: A Longitudinal Analysis in American Indians Aged 55 Years and Older.

(1) Background: American Indians are disproportionately affected by air pollution, an important risk factor for dementia. However, few studies have investigated the effects of air pollution on the risk of dementia among American Indians. (2) Methods: This retrospective cohort study included a total of 26,871 American Indians who were 55+ years old in 2007, with an average follow-up of 3.67 years. County-level average air pollution data were downloaded from land-use regression models. All-cause dementia was identified using ICD-9 diagnostic codes from the Indian Health Service's (IHS) National Data Warehouse and related administrative databases. Cox models were employed to examine the association of air pollution with dementia incidence, adjusting for co-exposures and potential confounders. (3) Results: The average PM2.5 levels in the IHS counties were lower than those in all US counties, while the mean O3 levels in the IHS counties were higher than the US counties. Multivariable Cox regressions revealed a positive association between dementia and county-level O3 with a hazard ratio of 1.24 (95% CI: 1.02-1.50) per 1 ppb standardized O3. PM2.5 and NO2 were not associated with dementia risk after adjusting for all covariates. (4) Conclusions: O3 is associated with a higher risk of dementia among American Indians.

Neuropathologic Burden and Dementia in Nonagenarians and Centenarians: Comparison of 2 Community-Based Cohorts

BACKGROUND AND OBJECTIVES: The aim of this study was to compare 2 large clinicopathologic cohorts of participants aged 90+ and to determine whether the association between neuropathologic burden and dementia in these older groups differs substantially from those seen in younger-old adults. METHODS: Autopsied participants from The 90+ Study and Adult Changes in Thought (ACT) Study community-based cohort studies were evaluated for dementia-associated neuropathologic changes. Associations between neuropathologic variables and dementia were assessed using logistic or linear regression, and the weighted population attributable fraction (PAF) per type of neuropathologic change was estimated. RESULTS: The 90+ Study participants (n = 414) were older (mean age at death = 97.7 years) and had higher amyloid/tau burden than ACT <90 (n = 418) (mean age at death = 83.5 years) and ACT 90+ (n = 401) (mean age at death = 94.2 years) participants. The ACT 90+ cohort had significantly higher rates of limbic-predominant age-related TDP-43 encephalopathy (LATE-NC), microvascular brain injury (µVBI), and total neuropathologic burden. Independent associations between individual neuropathologic lesions and odds of dementia were similar between all 3 groups, with the exception of µVBI, which was associated with increased dementia risk in the ACT <90 group only (odds ratio 1.5, 95% CI 1.2-1.8, p < 0.001). Weighted PAF scores indicated that eliminating µVBI, although more prevalent in ACT 90+ participants, would have little effect on dementia. Conversely, eliminating µVBI in ACT <90 could theoretically reduce dementia at a similar rate to that of AD neuropathologic change (weighted PAF = 6.1%, 95% CI 3.8-8.4, p = 0.001). Furthermore, reducing LATE-NC in The 90+ Study could potentially reduce dementia to a greater degree (weighted PAF = 5.1%, 95% CI 3.0-7.3, p = 0.001) than either ACT cohort (weighted PAFs = 1.69, 95% CI 0.4-2.7). DISCUSSION: Our results suggest that specific neuropathologic features may differ in their effect on dementia among nonagenarians and centenarians from cohorts with different selection criteria and study design. Furthermore, microvascular lesions seem to have a more significant effect on dementia in younger compared with older participants. The results from this study demonstrate that different populations may require distinct dementia interventions, underscoring the need for disease-specific biomarkers.