APOE and major depressive disorder: These factors can be classified as follows: (a) demographic risk factors, such as advanced age; (b) cardiovascular risk factors, such as diabetes mellitus, dyslipidemia, hypertension in middle age, and obesity in middle age (10); (c) modifiable lifestyle risk factors, such as sedentary lifestyle, smoking, and substance use (10); (c) genetic factors related to the apolipoprotein E (APOE) gene, a risk factor for Alzheimer's disease and related dementias; and psychiatric risk factors such as depression, psychological distress, and sleep disorders (11).