Disparities Persist in Dementia Risk of Black and White Adults

The ratio of dementia risk across non-Hispanic Black and White individuals in the United States does not appear to have changed between 2000 and 2016, researchers found in a study published in JAMA Neurology.

Several studies have reported that the risk of dementia is higher in non-Hispanic Black individuals than in non-Hispanic White individuals. Using data from the US Health and Retirement Study (HRS), a nationally representative study of adults aged 50 and older, the researchers sought to examine whether relative racial disparities in dementia in the US, both in terms of relative prevalence and relative incidence of dementia, changed from 2000 to 2016.

The researchers analyzed data from 9 HRS waves spanning 2000 through 2016. Each wave (which had a range of 6322 to 7579 eligible participants per wave) became a cross-sectional study to quantify racial disparities in the prevalence of dementia at 2-year intervals from 2000 through 2016. The researchers estimated trends in racial disparities over that time using the data from all 9 waves.

Subcohorts (which ranged in size from 5322 to 5961 participants) with 4 years of follow-up were nested within the larger longitudinal HRS to quantify racial disparities over calendar periods, with baseline years in 2000 to 2012. All subcohorts’ data was then combined.

Participants who had an algorithmic dementia diagnosis in the baseline year were excluded from subcohorts, and subcohort participants who did not have a diagnosis at the end of 2 waves of follow-up were censored.

The researchers conducted all analyses using the Expert Model, LASSO (least absolute shrinkage and selection operator), and Modified Hurd Algorithms, which predict dementia status based on sociodemographic characteristics, physical health, and cognitive health collected at HRS interview. All 3 algorithms were designed for use in HRS-based studies of racial and ethnic disparities in dementia by having similar out-of-sample sensitivity and specificity across non-Hispanic White and non-Hispanic Black subgroups.

The study authors applied HRS sampling weights to adjust for differential probability of inclusion and accounted for geographic stratification and clustering when estimating standard errors. Data from non-Hispanic Black and non-Hispanic White HRS participants who were aged 70 and older at each wave to whom they could assign an algorithmic dementia diagnosis were analyzed.  Weighted regression models were used to estimate crude dementia prevalence ratios and to estimate and quantify time trends in dementia incidence. Race-specific distribution of age and sex in the year 2000 were standardized.

The Expert Model and LASSO algorithms classified an average of 20% of participants as having dementia while the Modified Hurd algorithm classified 18% of participants as having dementia. All 3 algorithms found that non-Hispanic Black participants had about a 1.5 to 1.9 times higher prevalence of dementia compared with non-Hispanic White participants in all waves in both crude and standardized estimates.

Overall, dementia prevalence declined with time in both crude and standardized estimates, and point estimates suggested a slight decline in the crude prevalence ratio comparing the groups in later years, but relative dementia prevalence across both groups did not change substantially over time. After age and sex standardization, there was no evidence of a shrinking racial disparity over time.

Across all subcohorts, non-Hispanic Black participants had an approximately 1.4 to 1.8 times higher incidence of dementia in comparison with non-Hispanic White participants. Analyses using the Expert Model or Modified Hurd algorithms to ascertain dementia status suggested no change over time, whereas analyses using the LASSO model suggested declining dementia incidence with time only in age- and sex-standardized analyses.

Limitations of the study included the use of an algorithm to ascertain dementia and the focus on the prevalence and incidence of the clinical syndrome of dementia rather than biomarker-based diagnoses of Alzheimer disease.

“Although our findings suggest stable or declining dementia risk overall, we found no evidence to suggest that relative racial disparities in dementia risk have narrowed between 2000 and 2016,” the authors said.

Reference

Power MC, Bennett EE, Turner RW, et al. Trends in relative incidence and prevalence of dementia across non-Hispanic Black and White individuals in the United States, 2000-2016. JAMA Neurol. Published online November 30, 2020. doi:10.1001/jamaneurol.2020.4471