Prevalence and Incidence of Mild Cognitive Impairment across Subtypes, Age, and Sex.

OBJECTIVE

The purpose of this study was to report on the prevalence and incidence of mild cognitive impairment (MCI) across age, sex, and subtypes according to various criteria in a population-based sample.

METHODS

The sample was drawn from the Swedish Good Aging in Skåne (GÅS) population study, and data from 3,752 participants aged 60 years and more were used to calculate the MCI prevalence. The incidence was calculated using 2,093 participants with 6-year follow-up data. MCI was defined according to the expanded Mayo Clinic criteria: cognitive complaint, objective cognitive impairment (two different criteria depending on the severity of impairment), preserved functional abilities, and no dementia.

RESULTS

The prevalence estimates ranged from 5.13 to 29.9% depending on age and severity of impairment. The incidence rates of overall MCI were 22.6 (95% confidence interval [CI]: 19.6-25.9) and 8.67 (95% CI: 7.0-10.7) per 1,000 person-years for less severe and severe cognitive impairment, respectively. The highest prevalence and incidence estimates were found for "non-amnestic MCI single domain." The older age groups had a higher prevalence, and no sex or age differences in MCI incidence were detected.

CONCLUSION

Our findings concur with previous research advocating that MCI is a heterogeneous concept, since the prevalence and incidence estimates differed substantially according to age, MCI subtype, and severity of cognitive impairment.