Predictors of improvement or decline in instrumental activities of daily living among community-dwelling older Japanese

Background: To explore predictors of functional improvement or decline in instrumental activities of daily living (IADL) among community-dwelling older people. Methods: Of all the residents (≥65 years, n = 1,673) living in Yoita town, Niigata prefecture, Japan, in 2000, 1,544 subjects who participated in the baseline interview survey (T1) were followed up until 2002 (T2). A wide range of variables obtained in T1 was entered into the model predicting functional improvement or decline in IADL. Results: Among 1,274 individuals who participated in both T1 and T2, 105 subjects showed improvement, 194 decline, and the remaining 975 showed stability in IADL. Multiple logistic regression analyses indicated that good self-rated health and cognitive function (MMSE ≥24) at T1 were good predictors of both improvement and protection against decline in IADL. Independence in basic activities of daily living predicted improvement in IADL. Advanced age and poor walking ability predicted decline in IADL. Conclusions: Good self-rated health and cognitive function predicted both improvement and protection against decline in IADL. Thus, intervention programs aiming at maintaining both good self-rated health and cognitive function should be able to improve IADL.