Changes in TMIG‐Index of Competence by subscale in Japanese urban and rural community older populations: Six years prospective study

Objective: To examine the longitudinal changes in higher‐level functional capacity in Japanese urban and rural community older populations. Design: Population‐based cross‐sectional, and prospective cohort studies. Setting: Koganei city in a suburb of Tokyo, and Nangai village, Akita Prefecture, Japan. Participants: One thousand, five hundred and six older persons (793 in Koganei and 713 in Nangai) aged 65–83 years living at home. Main outcome measures: Disability in Instrumental Self‐Maintenance (IADL), Intellectual Activity or Social Role, measured by the Tokyo Metropolitan Institute of Gerontology Index of Competence. Results: At baseline, older men and women in the rural area, Nangai, had higher prevalence of disability in Intellectual Activity compared with respective counterparts in the urban area, Koganei. By contrast, disability in Social Role was more prevalent among elderly people in Koganei than in Nangai. In both areas older men and women had lowest prevalence of disability in IADL among three subscales. The six‐year longitudinal survey on older persons who had initially no disability in all three subscales demonstrated that in urban Koganei older persons were most likely to be disabled in Social Role with advancing age, followed in turn by Intellectual Activity and IADL. By contrast, elderly people in rural Nangai were most likely to be disabled in Intellectual Activity, followed by Social Role and instrumental ADL. The Cox‐proportional hazard model analysis for those who had no IADL disability at baseline revealed that the baseline level of Intellectual Activity or Social Role predicted significantly future onset of IADL disability in both areas even after controlling for sex, age, and chronic medical conditions. Conclusions: In both urban and rural community older populations, disability in Social Role and Intellectual Activity preceded IADL disability, and predicted significantly the future onset of IADL disability.