APOE and depressive symptom measurement: It is necessary to examine the effects of genetics (Apo E4), family history (PD or dementia), socioeconomic factors, lifestyle (drinking, smoking, caffeine, and exercise), lifestyle‐related diseases (hypertension, diabetes, and obesity), depression, head injury, and drugs other than those used for RBD treatment, which have been suggested to be associated with the risk of developing dementia.34