Study finds ‘no evidence’ that racial disparities in dementia have decreased

Rates and incidence of dementia among non-Hispanic Black individuals remained substantially higher compared with non-Hispanic white individuals in the U.S. from 2000 through 2016, according to findings published in JAMA Neurology.

“In the U.S., multiple studies report that the risk of dementia is higher in non-Hispanic Black individuals than in non-Hispanic white individuals,” the researchers wrote. “These disparities mirror those in other health domains, which are broadly attributed to the cumulative effects of structural racism; likewise, structural racism may affect brain health through material, behavioral and biological mechanisms.”

According to Melinda C. Power, ScD, associate professor in the department of epidemiology at George Washington University’s School of Public Health, and colleagues, the National Alzheimer Project aims, among other goals, to reduce these disparities in Alzheimer’s disease among racial and ethnic minorities at greater risk for the disease. To determine what progress has been made toward this goal, “it is essential” to track trends in racial disparities, the researchers noted, but no previous studies — to their knowledge — have examined national trends in the U.S. regarding racial and ethnic disparities in rates of dementia.

As a result, Power and colleagues aimed to determine whether relative racial disparities in dementia incidence in the U.S. widened, narrowed or remained stable between 2000 and 2016 using data from the nationally representative U.S. Health and Retirement Study. To address limitation of previous research, the researchers also determined dementia status with validated algorithms “designed to have similar performance across racial/ethnic groups” and reviewed secular trends in the prevalence and incidence of dementia across racial groups.

The Health and Retirement Study includes adults aged 50 years and older. The study recruits new participants every 6 years and study visits are done on a biennial basis, according to the study findings. Approximately 17,000 to 22,000 of respondents have been surveyed at each wave since 2000, achieving response rates of 81% to 89%. Power and colleagues collected data for this cohort study from non-Hispanic White and non-Hispanic Black participants aged 70 years and older from the 2000 to 2016 waves.

“For analyses of secular trends in racial disparities in dementia prevalence, each [Health and Retirement Study] wave was considered separately (range of participants meeting eligibility criteria in each wave, 6,322-7,579),” the researchers wrote. “For analyses of secular trends in racial disparities in dementia incidence, seven subcohorts were created (range of participants meeting eligibility criteria in each subcohort, 5,322-5,961).”

The researchers conducted follow-up among people without dementia for 4 years from subcohort baseline visits in 2000, 2002, 2004, 2006, 2008, 2010 and 2012. They analyzed data from October 2019 through August 2020, which included information on participant race/ethnicity based on answers from closed-ended survey questions.

Study findings demonstrated that the mean age and percentage of male participants eligible for inclusion in analyses of racial disparities in dementia prevalence increased over time among non-Hispanic white participants (from 78.2 years and 40% in 2000 to 78.7 years and 44% in 2016) but remained steady in non-Hispanic Black participants during the same period (from 78 years and 37% in 2000 to 77.9 years and 38% in 2016).

On average, across all years, 20% of participants were categorized as having dementia by the Expert Model and LASSO algorithms, while 18% were classified as having dementia with the Modified Hurd algorithm.

Findings from Power and colleagues showed that non-Hispanic Black participants experienced an approximately 1.5 to 1.9 times greater prevalence of dementia across all algorithms compared with non-Hispanic white participants in all waves from 2000 to 2016 in both crude and standardized estimates. Overall rates of dementia decreased with time in both crude and standardized analyses, but relative rates of dementia across non-Hispanic Black and non-Hispanic white participants did not change significantly over time. Standardizations for age and sex revealed no evidence of a declining racial disparity of time.

In all algorithms, non-Hispanic Black participants showed an estimated 1.4 to 1.8 times greater rate of dementia compared with non-Hispanic white participants across all subcohorts. Analyses quantifying overall time trends in rates of dementia showed varied results, according to the researchers.

“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,” Power and colleagues wrote.

While the results demonstrated stable or decreasing risk for dementia overall, the researchers found “no evidence” to indicate that relative racial disparities lessened from 2000 to 2016.

“Additional efforts to identify and mitigate factors contributing to these disparities is warranted,” Power and colleagues wrote. “Efforts to improve our capability to quantify and track dementia risk overall and by key sociodemographic groups are also needed. Such efforts would improve our ability to target interventions and track progress toward reducing both overall dementia risk and disparities in dementia risk.”