Racial/Ethnic Disparities in Risk and Protective Factors of Dementia in the United States

Background
Recent population-based studies show decline in dementia incidence and prevalence in high-income countries, suggesting that improved population cardiovascular health and rising levels of education in the past 25 years were associated with reduction of dementia risks. However, in the US, there is a variation in changes over time of educational attainment, prevalence and management of chronic diseases, and behaviors associated with poor cardiovascular health among racial/ethnic groups. This study examines the risk and protective factors associated with dementia and decomposes racial/ethnic disparities in factors associated with cognitive functioning.

Method
We performed a retrospective analysis of 3,495 older individuals (65+) in 2016 who participated in Harmonized Cognitive Assessment Protocol, linked to Health and Retirement Study to trace the individuals back to 2000. Using Mini-Mental State Examination (MMSE), individuals were classified as demented vs normal. Risk factors included were cardiovascular factors, hearing loss, and history of being uninsured in midlife, and current smoking, depression, and physical inactivity. Protective factors included were educational attainment. Using Oaxaca-Blinder decomposition, the relative contribution of different variables in explaining racial/ethnic disparities in cognitive functioning was evaluated.

Result
Accounting for sociodemographic, mid-, and later-life characteristics, Blacks have higher odds of having dementia, following Hispanics and Whites. Higher levels of education and wealth were associated with lower odds of dementia. History of stroke and hearing loss during mid-life, and depression and physical inactivity in late-life were associated with higher odds of dementia. The decomposition shows that about 32% of Blacks and Whites difference in MMSE score was explained by demographics and later-life characteristics, while nearly 68% of the difference remains unexplained. Comparing Whites and Hispanics, 70% of the difference in MMSE score was explained by demographics and later-life characteristics, while nearly 30% of the difference remains unexplained.

Conclusion
Blacks and Hispanics are found to have a higher risk of dementia compared to whites. Accounting for demographics, mid- and later-life risk and protective factors explain only one-third of the difference in cognitive functioning between Blacks and Whites and nearly two-thirds of the differences between Hispanics and Whites.