Causal mediation analyses (CMA) were performed using previously fitted logistic and linear models to estimate the mediating role of hippocampal volumes in the association between rs6859 and AD.<h4>Results</h4>We found that smaller HV significantly mediates the association between rs6859 in <i>NECTIN2</i> and AD risk. The gene discussed is NECTIN2; the disease is Alzheimer disease.