A Cognitive Turning Point in Development of Clinical Alzheimer's Disease Dementia and Mild Cognitive Impairment: A Biracial Population Study

Tau PET positivity predicts clinically relevant cognitive decline driven by Alzheimer's disease compared to comorbid cases; proof of concept in the ADNI study

β-amyloid (Aβ) pathology is not always coupled with Alzheimer's disease (AD) relevant cognitive decline. We assessed the accuracy of tau PET to identify Aβ(+) individuals who show prospective disease progression. 396 cognitively unimpaired and impaired individuals with baseline Aβ and tau PET and a follow-up of ≥ 2 years were selected from the Alzheimer's Disease Neuroimaging Initiative dataset. The participants were dichotomously grouped based on either clinical conversion (i.e., change of diagnosis) or cognitive deterioration (fast (FDs) vs. slow decliners (SDs)) using data-driven clustering of the individual annual rates of cognitive decline. To assess cognitive decline in individuals with isolated Aβ(+) or absence of both Aβ and tau (T) pathologies, we investigated the prevalence of non-AD comorbidities and FDG PET hypometabolism patterns suggestive of AD. Baseline tau PET uptake was higher in Aβ(+)FDs than in Aβ(-)FD/SDs and Aβ(+)SDs, independently of baseline cognitive status. Baseline tau PET uptake identified MCI Aβ(+) Converters and Aβ(+)FDs with an area under the curve of 0.85 and 0.87 (composite temporal region of interest) respectively, and was linearly related to the annual rate of cognitive decline in Aβ(+) individuals. The T(+) individuals constituted largely a subgroup of those being Aβ(+) and those clustered as FDs. The most common biomarker profiles in FDs (n = 70) were Aβ(+)T(+) (n = 34, 49%) and Aβ(+)T(-) (n = 19, 27%). Baseline Aβ load was higher in Aβ(+)T(+)FDs (M = 83.03 ± 31.42CL) than in Aβ(+)T(-)FDs (M = 63.67 ± 26.75CL) (p-value = 0.038). Depression diagnosis was more prevalent in Aβ(+)T(-)FDs compared to Aβ(+)T(+)FDs (47% vs. 15%, p-value = 0.021), as were FDG PET hypometabolism pattern not suggestive of AD (86% vs. 50%, p-value = 0.039). Our findings suggest that high tau PET uptake is coupled with both Aβ pathology and accelerated cognitive decline. In cases of isolated Aβ(+), cognitive decline may be associated with changes within the AD spectrum in a multi-morbidity context, i.e., mixed AD.

Statin Initiation and Risk of Incident Alzheimer Disease and Cognitive Decline in Genetically Susceptible Older Adults

BACKGROUND AND OBJECTIVES

The association of statin initiation with incident Alzheimer disease (AD) dementia and cognitive decline by the APOE ε4 allele is unknown. Our objective was to examine whether the association of statin initiation with incident AD dementia and cognitive decline differs by the APOE ε4 allele.

METHODS

This population-based longitudinal cohort study was conducted in 4 urban communities in Chicago, IL, United States, consisting of 4,807 participants. Statin initiation is based on the inspection of medications during home assessments. Clinical diagnosis for incident AD used the NINCDS-ADRDA criteria, and longitudinal measurements of global cognition consisted of episodic memory, perceptual speed, and the Mini-Mental State Examination tests.

RESULTS

The study participants had a mean age of 72 years, consisting of 63% female individuals and 61% non-Hispanic Black individuals. During the study period, 1,470 (31%) participants reported statin initiation. In a covariate-adjusted competing risk model, statin initiation was associated with a reduced risk of incident clinical AD [hazard ratio (HR) 0.81 (95% CI 0.70-0.94)] compared with nonusers. This association was statistically significantly lower (p interaction = 0.015) among participants with the APOE ε4 allele [HR 0.60 (95% CI 0.49-0.74)] compared with those without the APOE ε4 allele [HR 0.96 (95% CI 0.82-1.12)]. The annual decline in global cognition (β = 0.021, 95% CI 0.007-0.034) and episodic memory (β = 0.020, 95% CI 0.007-0.033) was also substantially slower among participants with the APOE ε4 allele after statin initiation compared with nonusers. However, the association of statin initiation with cognitive decline was not significant among those without the APOE ε4 allele.

DISCUSSION

Our findings suggest that statins might be associated with a lower risk of incident AD among individuals with the APOE ε4 allele. The benefits of statin therapy need further consideration in randomized clinical trials, especially among those with the APOE ε4 allele.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that among those aged 65 years or older, statin initiation was associated with a reduced risk of Alzheimer disease, especially in the presence of an APOE-e4 allele.

Episodic memory performance in a multi-ethnic longitudinal study of 13,037 elderly

Age-related changes in memory are not uniform, even in the absence of dementia. Characterization of non-disease associated cognitive changes is crucial to gain a more complete understanding of brain aging. Episodic memory was investigated in 13,037 ethnically diverse elderly (ages 72 to 85 years) with two to 15 years of follow-up, and with known dementia status, age, sex, education, and APOE genotypes. Adjusted trajectories of episodic memory performance over time were estimated using Latent Class Mixed Models. Analysis was conducted using two samples at baseline evaluation: i) non-cognitively impaired individuals, and ii) all individuals regardless of dementia status. We calculated the age-specific annual incidence rates of dementia in the non-demented elderly (n = 10,220). Two major episodic memory trajectories were estimated: 1) Stable-consisting of individuals exhibiting a constant or improved memory function, and 2) Decliner-consisting of individuals whose memory function declined. The majority of the study participants maintain their memory performance over time. Compared to those with Stable trajectory, individuals characterized as Decliners were more likely to have non-white ethnic background, fewer years of education, a higher frequency of ε4 allele at APOE gene and five times more likely to develop dementia. The steepest decline in episodic memory was observed in Caribbean-Hispanics compared to non-Hispanic whites (p = 4.3 x 10(-15)). The highest incident rates of dementia were observed in the oldest age group, among those of Caribbean-Hispanics ancestry and among Decliners who exhibited rates five times higher than those with Stable trajectories (11 per 100 person-years versus 3 per 100 person-years. Age, education, ethnic background and APOE genotype influence the maintenance of episodic memory. Declining memory is one of the strongest predictors of incident dementia.

Terminal decline of episodic memory and perceptual speed in a biracial population

We compared trajectories of terminal cognitive decline in older Black (n = 3372) and White (n = 1756) persons from a defined population who completed tests of episodic memory and perceptual speed at 3-year intervals for up to 18 years. During a mean of 9.9 years of observation, 1608 Black persons and 902 White persons died. Preterminal decline of episodic memory did not differ by race. Terminal episodic memory decline began earlier in Black persons (mean of 4.3 years before death) than in White persons (mean = 3.9 years) and progressed more slowly. By contrast, terminal decline of perceptual speed began earlier in White persons (mean = 5.0 years) than in Black persons (mean = 4.5 years). Rate of perceptual speed decline was more rapid in White persons than in Black persons in both the preterminal and terminal periods. The results indicate that terminal cognitive decline occurs in Black persons but suggest that the rate of cognitive decline during the terminal period is less rapid in Black persons than in White persons.

Secular Trends in Cognitive Performance in Older Black and White U.S. Adults, 1993-2012: Findings From the Chicago Health and Aging Project

Objective

To characterize secular trends from 1993 to 2012 in cognitive performance using a cohort of older black and white U.S. adults, and compare trends by race.

Method

Our data come from 8,906 participants of the Chicago Health and Aging Project (CHAP), a longitudinal, population-based cohort (age ≥ 67, 60% black). Participants underwent cognitive assessments in six 3-year study cycles from 1993 to 1996 through 2010 to 2012. We computed 3 measures of cognitive performance: global cognition, episodic memory, and perceptual speed.

Results

Mean performance in terms of global cognitive score followed a secular pattern of modest decline over the 6 study cycles. The trend was most pronounced for perceptual speed. Mean scores among black participants were consistently lower than those for whites; these disparities in mean performance narrowed over time, especially on perceptual speed, but appeared to widen at the last cycle. Global scores among the upper quartile of performers rose slightly, but scores among the lowest quartile of performers dropped precipitously.

Discussion

Between 1993 and 2012, secular trends in cognitive performance in this established cohort did not follow a clear pattern of improvement, contrasting with previous research. But patterns differed by cognitive domain, performance level, and race.

Risk of progression from subjective cognitive decline to mild cognitive impairment: The role of study setting

INTRODUCTION

We compared risk of progression from subjective cognitive decline (SCD) to mild cognitive impairment (MCI) in an academic memory clinic versus a population-based study.

METHODS

Older adults presenting at a memory clinic were classified as SCD (n = 113) or as noncomplainers (n = 82). Participants from a population study were classified as SCD (n = 592) and noncomplainers (n = 589) based on a memory complaint score. Annual follow-up performed for a mean of 3 years.

RESULTS

The adjusted hazard ratio for SCD was 15.97 (95% confidence interval: 6.08-42.02, P < .001) in the memory clinic versus 1.18 (95% confidence interval: 1.00-1.40, P = .047) in the population study, where reported "worry" about memory further increased SCD-associated risk for MCI.

DISCUSSION

SCD is more likely to progress to MCI in a memory clinic than the general population; participants' characteristics vary across settings. Study setting should be considered when evaluating SCD as a risk state for MCI and dementia.