A Longitudinal Study of Black-White Disparities in Cognitive Aging

PURPOSE: As the U.S. population of older adults continues to grow, age-related cognitive impairment and dementia will become a greater concern for public health since both increase with age. Studies have found that blacks are disproportionately affected by these conditions (Zsembik and Peek 2001, Schwartz, Glass et al. 2004, Mehta, Stewart et al. 2009, Potter, Plassman et al. 2009, Masel, Raji et al. 2010). Education, stressful life events and experiences of discrimination may account for, or modify, some of these differences by race in cognitive impairment over time. Additionally, religion and spirituality may protect against cognitive impairment in old age. The current study seeks to better understand black and white differences in changes in cognitive impairment by examining education, stressful life events, discrimination, religion and spirituality as both direct and moderating factors. METHODS: Analyses focused on black and white adults enrolled in all 5 waves (years 1986-2011) of the Americans' Changing Lives (ACL) study who were age 25 and older at baseline (N =3,617); additionally, a sub sample of adults was analyzed in waves 4 and 5. The outcome of cognitive impairment (or number of cognitive errors) was assessed at each wave using a shortened version of the Short Portable Mental Status Questionnaire (SPMSQ). A 9-item Recent Life Events Index was used to measure stressful life events and a 5-item adaptation of the Williams Everyday Discrimination Scale was used to measure discrimination. Mixed-effects models were used to examine the longitudinal relationship between race and cognitive impairment changes. OLS regression was used to model the relationships between education, stressful life events, discrimination, religion, spirituality and cognitive impairment while controlling for demographic characteristics such as age, gender, income and marital status as well as for risk factors known to influence cognition, including depressive symptoms, chronic health conditions and smoking status. RESULTS: The data showed that racial disparities in cognitive impairment existed at baseline such that blacks had higher cognitive impairment scores than whites. Second, these disparities widened over time (worsen with age) whereby blacks experience a more rapid cognitive decline than whites. Third, education alone, rather than the combined effect of education, recent stressful life events and discrimination, explained some of the race disparity. Fourth, religion and spirituality did not have a protective effect against cognitive impairment, such that those reporting high levels of religion and spirituality do not have lower levels of cognitive impairment versus those with low levels of religion and spirituality. Further, religion and spirituality also did not modify the race-cognition association.CONCLUSIONS: Study findings demonstrated that blacks have more cognitive impairment than whites at baseline and these disparities worsened with age, even after adjusting for sociodemographic and other health-related factors. This finding highlights that racial disparities begin earlier than previously identified. This study suggests that interventions designed to address cognitive decline should be implemented at younger ages. Moreover, education rather than stressful life events and discrimination accounted for a significant amount of racial disparities but did not fully explain black-white differences. Thus, the types of interventions developed should consider the underlying educational differences between black and white adults