Characterizing mild cognitive disorders in the young-old over 8 years: prevalence, estimated incidence, stability of diagnosis, and impact on IADLs.

Objectives: Few studies report incidence of mild cognitive impairment (MCI) and other mild cognitive disorders (MCD) in cohorts in their 60s, at an age when diagnoses are less stable. The authors' goal was to estimate the incidence and prevalence of MCI and MCD, characterize subgroups with stable vs nonstable diagnoses, and evaluate the impact of diagnosis on daily life in a young-old cohort.

Methods: A community-based cohort age 60 to 64 years in 1999 (n = 2551) was monitored for 8 years and assessed every 4 years. A two-stage sampling design was used to identify MCI and MCD through a neuropsychological and neurological assessment. A panel of physicians blind to previous diagnoses reviewed each case using published criteria.

Results: The prevalence of MCDs in the cohort aged 68 to 72 years at the last follow-up was approximately 10%. An estimated 141 subjects (7.7%) progressed to MCI and 183 subjects (10.0%) progressed to MCD between years 4 and 8. Only eight participants received a dementia diagnosis at any wave, five of whom progressed from MCDs. More than 45% of diagnoses were unstable during the 8 years of follow-up. Stable diagnoses were associated with lower Mini-Mental State Examination scores, history of neurological disorder, higher cardiovascular risk, and depression at baseline. MCDs were associated with impairments in instrumental activities of daily living and higher rates of reporting memory problems prior to diagnosis.

Conclusions: MCDs in individuals in their 60s occur in at least 10% of the population and are likely to be heterogeneous in terms of their etiology and long-term prognosis, but may cause a significant impact in everyday life.