Mild cognitive impairment, incidence, progression, and reversion: findings from a community-based cohort of elderly African Americans.

OBJECTIVE To examine the long-term outcomes of community-based elderly African Americans by following their transitions from normal cognition to mild cognitive impairment (MCI) to dementia. METHODS Participants were from the community-based Indianapolis Dementia Project. A total of 4,104 African Americans were enrolled in 1992 or 2001 and followed until 2009 with regularly scheduled evaluation of cognitive assessment. A two-stage sampling was used at each evaluation to select individuals for extensive clinical assessment following the results of Stage 1 cognitive testing. Age- and gender-specific incidence, progression, and reversion rates for MCI were derived using the person-year method in a dynamic cohort and predicted probabilities from weighted multinomial logistic models of transitional probabilities among normal cognition, MCI, and dementia. RESULTS Annual overall incidence rate for MCI was 5.6% (95% confidence interval [CI]: 4.6%-6.6%). Annual progression rate from MCI to dementia was 5.9% (95% CI: 5.3%-6.5%), and annual reversion rate from MCI to normal was 18.6% (95% CI: 16.7%-20.4%). Both MCI incidence rates and MCI to dementia progression rates increased with age, whereas reversion rates from MCI to normal decreased with age. CONCLUSION MCI progression to dementia was much more frequent in the older age groups than in younger participants where reversion to normal cognition is more common. Future research is needed to determine factors related to the heterogeneous outcomes in MCI individuals.