Predictive Validity of a New Instrumental Activities of Daily Living Scale for Detecting the Incidence of Functional Disability among Community-Dwelling Older Japanese Adults: A Prospective Cohort Study

Abstract

We examined the predictive validity of a newly developed scale—the National Center for Geriatrics and Gerontology Activities of Daily Living (NCGG-ADL)—to measure instrumental activities of daily living (IADL) ability. We tested the scale for detecting new incidences of functional disability among community-dwelling older Japanese adults. Participants were 2708 older adults (mean age = 79.0 years, 51.6% women) living in the community who had no functional decline at baseline. We assessed IADL ability using the NCGG-ADL scale, comprising 13 self-report questions. Next, we assessed their functional disability monthly for 24 months, based on the national long-term care insurance (LTCI) system. Among all participants, 430 (15.9%) had an IADL limitation at baseline, and 289 (10.7%) were newly certified as functionally disabled. Participants scoring ≤ 12 of 13 points in the NCGG-ADL showed a significantly higher risk of functional disability than did those scoring 13 points, even after adjusting for covariates (hazard ratio [95% confidence interval] = 1.58 [1.19–2.09]). We thus validated the NCGG-ADL as a screening tool for assessing the risk of functional disability among community-dwelling older Japanese adults. We conclude that IADL limitations, as measured by the NCGG-ADL, could be useful predictors of functional disability.