[The prevalence of mild cognitive impairment (MCI) among the community-dwelling elderly: findings from the 2nd Nakayama study].

To determine the prevalence of Mild Cognitive Impairment (MCI) in community dwelling elderly, a door to door population survey was carried out on all persons aged 65 years and older residing at home on the prevalence day (1 August 1999). All assessments were conducted by neuropsychiatrists. The diagnosis was made with the Geriatric Mental State (GMS)--Automated Geriatric Examination for Computed Assisted Taxonomy (AGECAT) (Copeland et al, 1986). AGECAT organicity levels 1 and 2 (sub-cases) are referred to as MCI. Of 1461 inhabitants, 1156 (79.1%) completed the protocol. The prevalence of MCI was 5.3%, with 1.7% organic brain syndrome level 2 and 3.6% organic brain syndrome level 1. MCI is associated with an increased risk of developing dementia. However, research on the prevalence of MCI has produced inconsistent data. The operational consensus criteria of MCI should be established for future community-based longitudinal study.