Prevalence of mild cognitive impairment is higher in men. The Mayo Clinic Study of Aging

Abstract

Objective: We investigated the prevalence of mild cognitive impairment (MCI) in Olmsted County, MN, using in-person evaluations and published criteria.

Methods: We evaluated an age- and sex-stratified random sample of Olmsted County residents who were 70-89 years old on October 1, 2004, using the Clinical Dementia Rating Scale, a neurologic evaluation, and neuropsychological testing to assess 4 cognitive domains: memory, executive function, language, and visuospatial skills. Information for each participant was reviewed by an adjudication panel and a diagnosis of normal cognition, MCI, or dementia was made using published criteria.

Results: Among 1,969 subjects without dementia, 329 subjects had MCI, with a prevalence of 16.0% (95% confidence interval [CI] 14.4-17.5) for any MCI, 11.1% (95% CI 9.8-12.3) for amnestic MCI, and 4.9% (95% CI 4.0-5.8) for nonamnestic MCI. The prevalence of MCI increased with age and was higher in men. The prevalence odds ratio (OR) in men was 1.54 (95% CI 1.21-1.96; adjusted for age, education, and nonparticipation). The prevalence was also higher in subjects who never married and in subjects with an APOE epsilon3epsilon4 or epsilon4epsilon4 genotype. MCI prevalence decreased with increasing number of years of education (p for linear trend <0.0001).

Conclusions: Our study suggests that approximately 16% of elderly subjects free of dementia are affected by MCI, and amnestic MCI is the most common type. The higher prevalence of MCI in men may suggest that women transition from normal cognition directly to dementia at a later age but more abruptly.

Figures

CME

Figure 1 Flow chart of the steps involved in the prevalence study Administrative exclusions involved 56 people who were terminally ill or in hospice and 114 who could not be contacted to confirm eligibility. All percentages refer to the total of 4,398 subjects considered eligible for the study.

Figure 2 Patterns of mild cognitive impairment (MCI) prevalence by age, sex, education, and type of MCI (A) Age- and sex-specific prevalence of MCI in Olmsted County, MN. Men had consistently higher prevalence than women at all ages. (B) Education- and sex-specific prevalence of MCI. The prevalence decreased with increasing education in both men and women. (C) Age- and type-specific prevalence of MCI. The increase of prevalence with age was consistent for single-domain amnestic MCI (SD a-MCI), multiple-domain amnestic MCI (MD a-MCI), single-domain nonamnestic MCI (SD na-MCI), and multiple-domain nonamnestic MCI (MD na-MCI). (D) Education- and type-specific prevalence of MCI. The decline in prevalence with increasing education was consistent across the 4 types of MCI.