Multimorbidity and Risk of Mild Cognitive Impairment.

Objectives: To determine the association between multiple chronic conditions and risk of incident mild cognitive impairment (MCI) and dementia.

Design: Prospective cohort study.

Setting: Olmsted County, Minnesota.

Participants: Cognitively normal individuals (N = 2,176) enrolled in the Mayo Clinic Study of Aging (MCSA).

Measurements: Participants were randomly selected from the community, evaluated by a physician, and underwent neuropsychometric testing at baseline and at 15-month intervals to assess diagnoses of MCI and dementia. Information on International Classification of Diseases, Ninth Revision codes for chronic conditions in the 5 years before enrollment was electronically captured using the Rochester Epidemiology Project medical records linkage system. Multimorbidity was defined as having two or more chronic conditions, and the association between multimorbidity and MCI and dementia was examined using Cox proportional hazards models.

Results: Of 2,176 cognitively normal participants (mean age ± standard deviation 78.5 ± 5.2; 50.6% male), 1,884 (86.6%) had multimorbidity. The risk of MCI or dementia was higher in persons with multimorbidity (hazard ratio (HR) = 1.38, 95% confidence interval (CI) = 1.05-1.82) than in those with one or no chronic condition. The HR was of greater magnitude in persons with four or more conditions (HR = 1.61, 95% CI = 1.21-2.13) than in those with two or three conditions (HR = 1.03, 95% CI = 0.76-1.39) and for men with multimorbidity(HR = 1.53, 95% CI = 1.01-2.31) than for women with multimorbidity (HR = 1.20, 95% CI = 0.83-1.74), compared to those with one or no chronic condition.

Conclusion: In older adults, having multiple chronic conditions is associated with greater risk of MCI and dementia. This is consistent with the hypothesis that multiple etiologies may contribute to MCI and late-life dementia. Preventing chronic diseases may be beneficial in delaying or preventing MCI and dementia.