Longitudinal changes in higher-level functional capacity of an older population living in a Japanese urban community

This study examined the present state and longitudinal changes in higher-level functional capacity in a Japanese urban community. Persons aged 65-84 years living in a suburb of central Tokyo participated in a baseline survey held in 1991 (n = 814) and followed-up for 8 years. Outcome measures were disabilities in: instrumental self-maintenance (IADL), the intellectual activity scale (intellectual activity) and the social role scale (social role), as measured by subscales of the Tokyo Metropolitan Institute of Gerontology Index of Competence (TMIG-index of competence). At baseline among the three subscales, both older men and women had the highest prevalence of disability in social role, followed in turn by intellectual activity and IADL disability. The 8-year longitudinal survey on subjects who had no initial disability (229 men and 235 women) in all three subscales of TMIG-index of competence demonstrated that they were most likely to lose social role function with advancing age, followed in turn by intellectual activity and IADL. The Cox proportional hazard model analysis for all 814 participants revealed that baseline level of social role and intellectual activity significantly predicted the new onset of IADL disability during the 8-year follow-up period even after controlling for gender, age, and chronic medical conditions. In summary, disability in social role and intellectual activity do not only likely precede IADL disability, but also predict significantly the future onset of IADL disability in a Japanese urban community older population.