Genes Related to Sperm Motility Are Under Recent Ongoing Selection in Two Shorebird Species With a Polygynous Mating System and Frequent Multiple Paternity.

Alzheimer's disease (AD) and related dementias (ADRD) affect nearly 7 million people in the United States over the age of 65 and are the fifth leading cause of death; furthermore, with the baby boomer generation advancing in age, by 2060, the prevalence of ADRD is expected to double. The reverberation of these progressive conditions across the health‐care landscape will be significant, imposing strain on the health‐care system and society as a whole, while creating substantial economic and psychological burden for both patients and caregivers. These challenges will magnify existing inequities in populations at higher risk for ADRD. Non‐Hispanic/Latino (NH) African Americans (AAs) face a disproportionate burden of disease, experiencing higher incidence, earlier onset, and faster rates of cognitive decline compared to NH White adults., , , Early identification of those at risk would be beneficial for implementing preventive measures and assessing interventions. Twin and family studies show that the genetic heritability of late‐onset ADRD is about 58% to 80%. Carrying two copies of the apolipoprotein E () ε4 allele represents the strongest known genetic risk factor for late‐onset AD and is present in approximately one third of ADRD cases;, , however, the risk associated with ε4 alleles has been shown to vary by global and local genetic ancestry., , Polygenic risk scores (PRS) may capture additional ADRD risk by aggregating effect sizes from thousands of common variants associated with dementia identified by genome‐wide association studies (GWASs). However, PRS performance in AAs remains underexplored due to the limited representation of AA participants in GWAS analyses. Whether a PRS associated with dementia differentially modifies the effect of ε4 across diverse populations remains unclear. Using the biracial, longitudinal Chicago Health and Aging Project (CHAP), we examined associations between dementia PRS and incident ADRD and measures of cognition and cognitive decline, while accounting for ε4 alleles.