二次予防事業対象者の認知機能とビタミンD

Abstract

Cognitive impairment is the second leading cause of long-term care, and the number of cognitively impaired elderly individuals is increasing. Cognitive impairment has been reported to be associated with a low vitamin D level. However, many elderly individuals are deficient in vitamin D due to undernutrition and a house-bound status. It is unknown whether cognitive impairment is independently associated with the vitamin D level. The aim of this study was to examine the association between cognitive impairment and the levels of vitamin D among community-dwelling Japanese pre-frail elderly individuals. A cross-sectional survey was conducted in two towns (latitude: 36 degrees north) from June 2006 to January 2011. The subjects included 316 community-dwelling pre-frail elderly individuals 65 years of age or older (mean±SD: 77.0±5.7 yr) who attended a program for nursing care prevention. A questionnaire-based interview was conducted regarding activities of daily living. The serum levels of intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured. Age and gender were recorded, as well as the presence of cognitive impairment determined according to the Mini Mental State Examination (MMSE). The factors associated with an MMSE score of ≤23 were examined using a multiple logistic regression analysis. Of the subjects, 21.2% were men and 30.6% had an MMSE score of ≤23. The mean MMSE score was 25.3±3.7. The prevalence of severe deficiency of 25(OH)D was 1.7%, and only 14.0% of the participants had a sufficient vitamin D level. The multiple logistic regression analysis suggested that an MMSE score of less than 23 was significantly associated with the levels of iPTH and 25(OH)D among the pre-frail men, but not the women. Our data suggest that the vitamin D level is significantly associated with cognitive impairment in pre-frail elderly men.