Incidence of mild cognitive impairment: a systematic review.

BACKGROUND/AIMS Subjects with mild cognitive impairment (MCI) constitute a risk population of developing dementia and thus a population of clinical interest. This study reviews recent work on the incidence of MCI in the elderly. METHODS Incidence papers were identified by a systematic literature search. Studies on the incidence of MCI were considered if they identified 'cognitively mildly impaired' subjects by application of the MCI criteria, used the 'person-years-at-risk' method, and were based on population- or community-based samples. RESULTS Nine studies were identified. The incidence of amnestic MCI subtypes ranged between 9.9 and 40.6 per 1,000 person-years, and the incidence of non-amnestic MCI subtypes was 28 and 36.3 per 1,000 person-years. Regarding any MCI, incidence rates of 51 and 76.8 per 1,000 person-years were found. A higher risk of incident MCI mainly resulted for higher age, lower education and hypertension. DISCUSSION The incidence rates of MCI varied widely, and possible risk factors for incident MCI were analysed only to a limited extent. The findings call for an agreement concerning the criteria used for MCI and the operationalisation of these criteria.