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Black and White Differences in Cognitive Function Test Scores: What Explains the Difference?

Associates from the Health, Aging and Body Composition (Health ABC) study, a study of 3,075 adults aged 70 to 79 (mean age 74, 52% female, 42% black) were evaluated. Member characteristics and performance on 2 cognitive role tests (the modified Mini-Mental State Examination (3MS) and Digit Symbol Substitution test (DSS)) were assessed in 1997–98. Important correlates on bivariate tests (α = 0.10) were sequentially added in blocks (demographic, psychosocial, health-related, and socioeconomic) to generalized linear models, with 3MS or DSS score as the dependent variable. Mean raw 3MS score was 7 points lower in black than white participants (86.0 vs. 93.0; P<.001). After adjustment for demographic, psychosocial, health-related, and socioeconomic characteristics, the 7-point variation was reduced to 1 point. Thus, covariate adjustment explained 86% of the change in 3MS scores between blacks and whites (P<.001). Socioeconomic indicators, particularly literacy, education, and income, explained most of the variation in cognitive scores. Similar results were found using the DSS. Findings recommend that participant characteristics not only independently affect cognitive test scores, but they also explain most of the observed variation in cognitive performance between older blacks and whites. Given that socioeconomic status indicators, literacy level, in particular, may reflect early-life learning experiences, poor cognitive test performance may not reliably indicate a cognitive decline in economically disadvantaged populations.

Several studies report variation in cognitive test scores across ethnic groups, with older black and Latino adults having lower scores than older white adults.1–4 A recent study conducted in participants from the Cardiovascular Health Study recommends that rates of dementia also vary between blacks and whites, with the prevalence being higher in black men (22.2%) and women (23.4%) than in white men (13.5%) and women (14.5%).5,6 Some recommends that the validity of tests used to measure cognitive performance and screen for dementia may vary by population subgroup and have low specificity in nonwhite elders.7 Others report that discrepancies on cognitive test scores may be attributed to early-life or life-course disadvantages regarding education quality8,9 or meaningful variation in health status and the presence and severity of diseases and conditions known to influence cognitive performance.10,11 Few studies have had adequate data on socio economic status (SES) and health-related factors to begin to disentangle social versus health effects.

This study’s primary hypothesis was that variation This study’s primary hypothesis was that variation in cognitive test scores between black and white elders stem from variations in psychosocial, health-related, and socioeconomic factors. The aim was to explore how these characteristics might mediate the observed variation in cognitive function test scores between older black and white adults using data from the Health, Aging and Body Composition (Health ABC) study. This cohort is ideally suited to address variation between older black and white adults’ cognitive performance cause it consists of more than 3,000 well-functioning community-resident men and women aged 70 to 79 of whom 42% are black. Also, key explanatory characteristics were carefully measured at baseline or in the early follow-up years. The goal was to identify the magnitude of variation in cognitive function test scores between black and white elders and to determine the degree to which health-related, psychosocial, and socioeconomic factors reduce or eliminate these variations.