In a paper published in PLOS Genetics, a team from the University of Miami, Case Western Reserve University, Indiana University, and elsewhere describe a variant that appears to reduce Alzheimer's disease (AD) risk in individuals with African ancestry who have an AD-related risk allele in apolipoprotein E (APOE). Using directly assessed and imputed SNP profiles for 1,850 African-American individuals with AD and more than 4,300 unaffected controls from the same population, the team focused in on a chromosome 19 variant called rs10423769_A that seemed to protect against AD in African ancestry individuals with the APOE epsilon 4 risk allele — results they replicated with whole-genome sequence or DNP data for thousands of individuals from cohorts enrolled in Nigeria, an admixed population in Puerto Rico, or non-Hispanic White individuals. "This finding is the first [African ancestry] specific protective effect in AD and highlights the importance of diversity and the inclusion of all populations in research," the authors write. "It will hopefully encourage additional studies focused on diverse populations, where allelic frequency differences can discover information that is hidden when studying only a single population."