Sleep Disturbances and Depression Associated With Cognitive Function As Well As Activities of Daily Living in Older Adults With Very Mild to Mild Dementia

Objective: The present study compared cognitive function and the ability to perform daily activities in subjects with very mild to mild dementia, classified by the presence or absence of sleep disturbances and depression. Methods: A total of 1,188 psychiatric outpatients (457 males and 731 females, mean age=74.65±5.83 years) were recruited. Sleep disturbances were measured by the Korean version of the Neuropsychiatric Inventory and depression was measured by the Korean Geriatric Depression Scale. Cognitive function was assessed using the Korean version of the Mini-Mental State Examination (K-MMSE), immediate recall, delayed recall, and verbal fluency. The ability to perform daily tasks was measured by the Seoul-Instrumental Activities of Daily Living (S-IADL). Results: Participants with both sleep disturbances and depression as well as those with depression only had significantly lower K-MMSE, immediate and delayed recall, and verbal fluency scores and higher S-IADL scores than the normal group. Also, those with both sleep disturbances and depression showed the highest S-IADL scores among groups. However, there were no significant differences between subjects with sleep disturbances only and the normal group in all cognitive functional areas and S-IADL. Conclusion: The present study found the differences in cognitive function and the ability to perform daily tasks among patients with mild dementia according to their sleep disturbances and depression. Our findings suggest that depression has stronger associations with cognitive and functional decline in older adults than sleep disturbances.