Racial and ethnic minority representation in dementia risk factor research: a scoping review of cohort studies

Despite a potentially greater burden of dementia, racial and ethnic minority populations around the world may be more likely to be excluded from research examining risk factors for incident dementia. We aimed to systematically investigate and quantify racial and ethnic minority representation in dementia risk factor research.

We performed a two-stage systematic search of databases-MEDLINE (Ovid SP), Embase (Ovid SP) and Scopus-from inception to March 2021 to identify population-based cohort studies looking at risk factors for dementia incidence. We included cohort studies which were population-based and incorporated a clinical dementia diagnosis.

Out of the 97 identified cohort studies, fewer than half (40 studies; 41%) reported the race or ethnicity of participants and just under one-third (29 studies; 30%) reported the inclusion of racial and ethnic minority groups. We found that inadequate reporting frequently prevented assessment of selection bias and only six studies that included racial and ethnic minority participants were at low risk for measurement bias in dementia diagnosis. In cohort studies including a multiethnic cohort, only 182 out of 337 publications incorporated race or ethnicity in data analysis-predominantly (90%) through adjustment for race or ethnicity as a confounder. Only 14 publications (4.2% of all publications reviewed) provided evidence about drivers of any observed inequalities.

Racial and ethnic minority representation in dementia risk factor research is inadequate. Comparisons of dementia risk between different racial and ethnic groups are likely hampered by significant selection and measurement bias. Moreover, the focus on 'adjusting out' the effect of race and ethnicity as a confounder prevents understanding of underlying drivers of observed inequalities. There is a pressing need to fundamentally change the way race, ethnicity and the inclusion of racial and ethnic minorities are considered in research if health inequalities are to be adequately addressed.