There is controversy however, from conflicting studies that show a lack of association between cognitive function in PD with the APOE ε4 status (Mengel et al., 2016), which some may have attributed to sex-specific effects due to findings of steeper cognitive decline in male PD patients carrying the ε4 allele that contrasts the lack of interaction in female subjects (Kim et al., 2021a). The gene discussed is APOE; the disease is Mental deterioration.