Prevalence of depression and depressive symptoms among older Japanese people: comorbidity of mild cognitive impairment and depression

Background: The aim of the study was to estimate the prevalence of DSM-III-R major depressive episodes (MDEs), depressive symptoms cases (DSCs) (defined as a score of >= 6 on the Geriatric Depression Scale but falling short of MDE), and coexisting mild cognitive impairment (MCI) among Japanese community-dwelling older people. Methods: Prevalence was estimated based on screening evaluation, individual interviews, and doorto- door visits. MDE and DSC were diagnosed, and the cognitive status of the participants was determined to be dementia, MCI, or normal. Results: A total of 1888 subjects of 2698 candidates (70.0%) participated. The prevalence of MDE and DSC were estimated to be 4.5% (95% CI, 3.4-6.0) and 11.5% (95% CI, 4.2-28.0), respectively. MCI was more prevalent in subjects with depression (26.2%) than those with normal mood (17.9%). Although no prototypical profile of cognitive dysfunction was revealed, multiple MCI was more prevalent in subjects with depression (12.2%) than subjects with normal mood (3.8%). Conversely, subjects with MCI (26.3%) were more likely to develop depression compared with those with normal cognitive function (18.0%). Conclusions: The prevalence of depression in our subjects seems to be similar with that of previous studies. MCI was more prevalent in subjects with depression than those with normal mood. Individuals with depression showed no particular association with any of the four MCIs. Given that depression and MCI are often associated with each other and that MCI is a predictor for development of dementia, the risk of developing dementia in the depressed older people with coexisting MCI should be acknowledged. Copyright (C) 2011 John Wiley & Sons, Ltd.