• Hyuma Makizako, Hiroyuki Shimada, Takehiko Doi, Kota Tsutsumimoto, Ryo Hotta, Sho Nakakubo, Keitaro Makino, and Takao Suzuki.
• Department of Preventive Gerontology, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Aichi, Japan.
• J. Alzheimers Dis. 2016 Oct 18; 54 (4): 1473-1482.

BackgroundOlder adults with mild cognitive impairment (MCI) are non-demented, but demonstrate cognitive dysfunction, and have significantly higher risk of progressing to dementia. A better understanding of more sensitive risk factors, such as combination of cognitive and psychological status, for progression of MCI to dementia may be crucial for prevention of development of dementia.ObjectiveTo examine MCI, depressive symptoms, and comorbid MCI and depressive symptoms as risk factors for development of dementia.MethodsA total of 3,663 community-dwelling older people were included in this prospective longitudinal study. MCI was determined by age- and education-adjusted objective cognitive impairment using computerized comprehensive cognitive measures including memory, attention/executive function, and processing speed. Depressive symptoms were measured using the 15-item Geriatric Depression Scale (GDS) and defined by a GDS score of 6 or more.ResultsDuring the 24-month follow-up period, 72 participants (2.0%) developed dementia. Baseline MCI was significantly associated with an increased risk of incident dementia (hazard ratio [HR], 3.2; 95% confidence interval [CI], 1.8-5.5) but depressive symptoms were not (2.0; 1.0-4.2) after adjusting for age, sex, education, prescribed medications, and walking speed. Participants with comorbid MCI and depressive symptoms at baseline had a higher risk of developing dementia (HR, 4.8; 2.3-10.5).ConclusionAlthough MCI and depressive symptoms may be associated with increased risk for incident dementia independently, comorbid MCI and depressive symptoms have a significantly greater impact on dementia development among community-dwelling older adults.

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