Many studies have supported the notion, including those that revealed significantly lower cognitive domain scores (Pavlova et al., 2014), or higher odds of subsequent dementia and earlier dementia onset among PD APOE ε4 carriers, and longitudinal studies revealing a more rapid decline in PD APOE ε4 carriers (Morley et al., 2012). The gene discussed is APOE; the disease is Parkinson disease.