Early evidence that AD has a genetic component came from studies showing significant familial aggregation of the disorder (Cotton, 1979). Although environmental factors play a significant role in AD risk, twin and family-based studies have consistently demonstrated a heritability of approximately 50% (Heath et al., 1997; Kendler et al., 1992; McGue et al., 1992; Prescott and Kendler, 1999; Reed et al., 1996; True et al., 1999; Verhulst et al., 2014). Identifying genes that influence risk for AD will inform our knowledge of the mechanisms underlying the disorder, potentially improving its diagnosis, treatment and prevention.
