For how many days and what types of group activities should older Japanese adults be involved in to maintain health? A 4-year longitudinal study.

Studies have suggested that frequent participation in social groups contributes to the well-being of older people. The primary aim of this study was to identify the number of days older adults should participate in the activities of social groups to maintain their health for 4 years. This study also aimed to examine whether the effective frequency differs by the type of social group activity.We examined a prospective cohort of 1,320 community-dwelling older adults over 65 years of age, who responded to both a baseline and a follow-up mail survey, in a suburban city of Tokyo, Japan. The dependent variable was the change in functional competence during 4 years. Logistic regression analyses were conducted to examine the effects of participation in the activities of the 5 most common social groups among older Japanese on maintaining functional competence.Nine hundred and ninety-four participants (76.5%) maintained their functional competence for 4 years. The results of the logistic regression analyses showed that participating in alumni groups less than once a month and being an inactive member were associated with higher odds of maintaining functional competence, after controlling for socioeconomic, demographic and baseline health status. Additionally, the odds of maintaining functional competence for 4 years increased upon participating in volunteer groups once a month or more. These results were also confirmed using logistic regression analysis, even after adjustment for the effects of participation in other social groups.The results indicated the effectiveness of volunteer activities that fulfill a social role in maintaining health. Therefore, older adults should be encouraged to participate in activities of volunteer groups at least once a month. Additionally, older adults can obtain positive health outcomes through less frequent participation in alumni groups, compared with the activities of volunteer groups