Age-associated cognitive changes in community dwelling adults

National Institute On Aging

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Abstract

Uric acid, a waste metabolite among humans, is linked to various cognitive outcomes. Using data from the Healthy Aging in Neighborhoods of Diversity across the Life Span study, 2004-2009 (visit 1) and 2009-2013 (visit 2) we examined sex and age-group specific associations of baseline serum uric acid (SUAbase) and significant change in SUA (DeltaSUA: 1 versus 0 = decrease versus no change; 2 versus 0 = increase versus no change) with longitudinal annual rate of cognitive change among a large sample of urban adults. Of 3,720 adults selected at baseline (age range: 30-64 y), complete data were available for N = 1,487-1,602 with a mean repeat of 1.5-1.7 visits/participant. Cognitive test domains spanned attention, processing speed, learning/memory, executive function, visuo-spatial/visuo-construction ability, language/verbal, and global cognitive function. SUA was measured at both visits. Multiple mixed-effect regression analyses were conducted. In the total population, a higher SUAbase was associated with a faster annual rate of decline on a measure of visual memory/visuo-construction ability (the Benton Visual Retention Test) by gamma= 0.07 with a standard error of 0.02, p < 0.001. Among older men, a significant increase in SUA was associated with slower decline on a test of attention/processing speed, namely Trailmaking test, Part A, measured in seconds to completion (gamma= -6.91+/-1.73, p < 0.001). In sum, a higher SUAbase was associated with faster cognitive decline over-time in a visual memory/visuo-construction ability test. DeltaSUA had particular beneficial effects of an increasing DeltaSUA on the domain of attention/processing speed among older men. The results suggest that more longitudinal studies are needed to examine cognitive domain-specific effects of over-time change in SUA within sex and age groups. Although both high and low levels of total and low-density lipoprotein (LDL) cholesterol have been associated with poor neuropsychological function, little research has examined nonlinear effects. In this study, we examined quadratic relations of cholesterol to performance on a comprehensive neuropsychological battery.Participants were 190 older adults (53% men, ages 54-83) free of major medical, neurologic, and psychiatric disease. Measures of fasting plasma total and high-density lipoprotein (HDL) cholesterol were assayed, and LDL cholesterol was calculated. Participants completed neuropsychological measures of attention, executive function, memory, visuospatial judgment, and manual speed and dexterity. Multiple regression analyses examined cholesterol levels as quadratic predictors of each measure of cognitive performance, with age (dichotomized as <70 vs. 70+) as an effect modifier. A significant quadratic effect of Total Cholesterol2 x Age was identified for Logical Memory II (b = -.0013, p = .039), such that the 70+ group performed best at high and low levels of total cholesterol than at midrange total cholesterol (U-shaped) and the <70 group performed worse at high and low levels of total cholesterol than at midrange total cholesterol (inverted U shape). Similarly, significant U- and J-shaped effects of LDL Cholesterol2 x Age were identified for Visual Reproduction II (b = -.0020, p = .026) and log of the Trail Making Test, Part B (b = .0001, p = .044). Quadratic associations between HDL cholesterol and cognitive performance were nonsignificant. Results indicate differential associations between cholesterol and neuropsychological function across different ages and domains of function. High and low total and LDL cholesterol may confer both risk and benefit for suboptimal cognitive function at different ages. In a related study, we examined age, sex, race, and socioeconomic status as modifiers of the association between carotid intimal medial thickness (IMT) and neurocognitive performance in a socioeconomically diverse, biracial, urban, adult population. Participants were 1712 community-dwelling adults (45% men, 56% African-American, 38% below poverty threshold, aged 30-64 years) enrolled in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Participants underwent initial carotid ultrasonography followed by cognitive testing on up to two occasions over 4 years. Mixed-effects regression analyses were adjusted for demographic, behavioral, and biomedical covariates. Significant cross-sectional IMT x race x poverty interactions were identified for measures of delayed recall memory, auditory-verbal attention, and working memory. An IMT x race interaction also appeared for auditory-verbal learning. Higher IMT was generally associated with worse cognitive performance, but the disadvantage was most pronounced among those with higher socioeconomic status and white participants. No longitudinal associations were identified. Carotid IMT-cognition associations differed as a function of race and socioeconomic status and were most compelling for measures of attention, executive function, and memory. These findings highlight the possibility that subclinical atherosclerosis may be differentially informative as a predictor of cognitive performance among varied demographic subgroups. In a fourth study, we examined cognitive performance and potential interactions of diet quality with race and poverty status using baseline data from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Poor diet quality contributes to morbidity, including poor brain health outcomes such as cognitive decline and dementia. African Americans and individuals living in poverty may be at greater risk for cognitive decrements from poor diet quality. Participants were 2090 African Americans and Whites (57 % female, mean age=47.9 years) who completed two 24 h dietary recalls. Healthy Eating Index-2010 (HEI-2010) scores were calculated and interpreted using federal guidelines. A neurocognitive test battery was administered to evaluate cognitive function over several domains. Linear regression analyses showed that lower HEI-2010 scores were associated with poorer verbal learning and memory (P<0.05) after adjustment for covariates. Diet quality within the sample was poor. Significant interactions of HEI-2010 and poverty status (all P<0.05) indicated that higher diet quality was associated with higher performance on tests of attention and cognitive flexibility, visuospatial ability and perceptual speed among those below the poverty line. No significant race interactions emerged. Higher diet quality was associated with better performance on two measures of verbal learning and memory, irrespective of race and poverty status. Findings suggest that diet quality and cognitive function are likely related at the population level. Future research is needed to determine whether the association is clinically significant.