Update on the Racial Diversity of Neuroimaging Studies Examining Obesity and Type 2 Diabetes

Background: Rates of obesity are higher in African-Americans and Hispanics compared to Whites. Type 2 Diabetes differentially affects American Indians, non-Hispanic African-Americans and Hispanics relative to non-Hispanic Whites. Our previous analysis of neuroimaging meta-analyses examining obesity and Type 2 Diabetes found the reporting of the racial diversity of samples to be lacking. This analysis updates these findings. Methods: Relevant neuroimaging meta-analyses of obesity and Type 2 Diabetes were sought by searching PubMed up to 1/22/2020. Of 126 records, 52 were duplicates. Of the 74 abstracts screened, 6 were excluded; of the 68 left, 60 were excluded, because these imaged parts of the body other than the brain (27/60); were not about obesity/diabetes (24/60); did not involve imaging (5/60) or were not an meta-analysis of imaging (5/60). This yielded 8 imaging meta-analyses of obesity (6/8) or Type 2 Diabetes (2/8). Results: In the 6 neuroimaging meta-analyses of obesity, we found the majority of studies conducted in the US reported the sex and the age of their sample (41/43, 95%). However, only 17/43 studies (40%) reported the racial diversity of their sample. The proportion of African-Americans represented in these studies (16%) greatly under-represented the rate of obesity in African-Americans in the USA (46.8%). In the two meta-analyses examining Type 2 Diabetes, only 1 of 14 US studies (7%) reported the racial diversity of their sample, with 1/14 studies reporting a predominately (82.2%) Caucasian sample. This sampling greatly underrepresented the rate of Type 2 Diabetes in American Indian/Alaska Natives (14.7%), Hispanics (12.5%), African-Americans (11.7%) and Asian Americans (9.2%), overrepresenting non-Hispanic whites (7.5%). Conclusions: The lack of reporting of the racial diversity of samples in neuroimaging studies included in meta-analyses of obesity and Diabetes Mellitus, Type 2, continue to fail to reflect the reality of these rates across diverse groups in the USA.