Racial Inequities in Cognitive Decline of Middle-Aged and Older Adults

Racial and ethnic minority groups experience higher burden of cognitive decline but are usually underrepresented in cognition-related research, particularly in cohort studies. We aimed to examine the trajectory of cognitive function over approximately 9 years according to race and ethnicity groups. We analyzed data from the Estudo Longitudinal de Saude do Adulto (ELSA-Brasil) study. Participants (35-74 years) were enrolled between 2008 and 2010 and followed up between 2017 and 2019. We categorized participants based on self-reported information into Black, Brown (mixed race), and White groups. We evaluated global and domain-specific (memory, verbal fluency, and executive function) cognitive function at baseline and follow-up, considering incident cognitive impairment as a global cognitive function score at follow-up lower than -1.5 SD from the baseline mean. We investigated the trajectory of cognitive decline according to race and ethnicity groups through cubic spline linear mixed-effects models with random intercept and slope. Relative risk and the difference in median age at onset of cognitive impairment were examined using Poisson and Laplace regression models, respectively. Participants (N = 10,308; 56% female) had a mean baseline age of 50.7 years. We observed lower global and domain-specific scores at baseline in Black (n = 1,510) and Brown (mixed race) (n = 2,902) than in White (n = 5,896) participants, with inequities increasing with aging. Declines in global cognitive function, memory, and executive function were faster from early to mid-adulthood in Brown (mixed race) than in White adults. The incidence of cognitive impairment in Black and Brown (mixed race) was 3 times that in White participants, when adjusting for study center, age, and sex. Their onset of cognitive impairment occurred 9.6 (95% CI 8.1-11.1) and 9.4 (95% CI 8.0-10.7) years earlier, respectively. In participants with ≤8 years of schooling, the incidence of cognitive impairment was 90% (95% CI 85%-97%) and 82% (95% CI 73%-96%) higher in Black and Brown (mixed race) than in White adults, whereas in those with ≥12 years, differences were 36% (95% CI 4%-57%) and 68% (95% CI 58%-74%), respectively. Our findings revealed early and marked racial inequities in global and domain-specific cognitive function in middle-aged and older Brazilian adults, particularly among those of lower schooling.