Mortality in mild cognitive impairment varies by subtype, sex, and lifestyle factors: the Mayo Clinic Study of Aging.

BACKGROUND: Etiologic differences in mild cognitive impairment (MCI) subtypes may impact mortality.

OBJECTIVE: To assess the rate of death in MCI overall, and by subtype, in the population-based Mayo Clinic Study of Aging.

METHODS: Participants aged 70-89 years at enrollment were clinically evaluated at baseline and 15-month intervals to assess diagnoses of MCI and dementia. Mortality in MCI cases versus cognitively normal (CN) individuals was estimated using Cox proportional hazards models.

RESULTS: Over a median follow-up of 5.8 years, 331 of 862 (38.4%) MCI cases and 224 of 1,292 (17.3%) cognitively normal participants died. Compared to CN individuals, mortality was elevated in persons with MCI (hazard ratio [HR] = 1.79; 95% CI: 1.41 to 2.27), and was higher for non-amnestic MCI (naMCI; HR = 2.40; 95% CI: 1.72 to 3.36) than for amnestic MCI (aMCI; HR = 1.61; 95% CI: 1.25 to 2.09) after adjusting for confounders. Mortality varied significantly by sex, education, history of heart disease, and engaging in moderate physical exercise (p for interaction <0.05 for all). Mortality rate estimates were highest in MCI cases who were men, did not exercise, had heart disease, and had higher education versus CN without these factors, and for naMCI cases versus aMCI cases without these factors.

CONCLUSIONS: These findings suggest stronger impact of etiologic factors on naMCI mortality. Prevention of heart disease, exercise vigilance, may reduce MCI mortality and delayed MCI diagnosis in persons with higher education impacts mortality.