The differential effects of type and frequency of social participation on IADL declines of older people

Background Although social participation (SP) is valid in active aging, it is vague which types and the frequency of SP are effective in maintaining instrumental activities of daily living (IADL). We conducted a community-based prospective cohort study and investigated the association of the types and frequency for SP with IADL decline in community-dwelling older adults. Methods The target population were all individuals aged ≥65 living in a commuter town in Nara, Japan. A total of 6,013 participants with independent IADL at baseline were analyzed. IADL was assessed using the Tokyo Metropolitan Institute of Gerontology Index of Competence. Six SP types were assessed: volunteer groups, sports groups, hobby clubs, senior citizens’ clubs, neighborhood community associations, and cultural clubs. The frequency of SP was categorized into frequent (i.e., weekly or more), moderate (i.e., monthly or yearly), and non-participation. Using multiple logistic regression models, the odds ratio (OR) and a 95% confidence interval (CI) for IADL decline were calculated. Covariates included age, marital status, education, subjective economic status, work status, body mass index, chronic medical conditions (i.e., hypertension, diabetes mellitus, heart disease, and cerebrovascular disease), lifestyle factors (i.e., alcohol, smoking, and exercise), self-rated health, depression, and cognitive functioning. To examine gender differences, stratified analyses by gender were performed. Results During the 33-month follow-up, 16.4% of men and 8.7% of women exhibited IADL decline. After adjustment for all covariates, compared to those who never participated, women with moderate participation had significantly lower odds of IADL decline in volunteer groups (OR = 0.53, 95% CI = 0.31–0.88), hobby clubs (OR = 0.55, 95% CI = 0.38–0.79), neighborhood community associations (OR = 0.58, 95% CI = 0.42–0.81), and cultural clubs (OR = 0.51, 95% CI = 0.31–0.82), and women with frequent participation had lower odds of IADL decline in hobby clubs (OR = 0.63, 95% CI = 0.43–0.93). In contrast, among men, the significant association between SP and less risk of IADL decline was limited to moderate participation in neighborhood community associations (OR = 0.79, 95% CI = 0.63–0.99), and there were no differences between frequent participation and non-participation in all types of SP. Regarding volunteer groups, compared to women with frequent participation, women with moderate participation had a significantly lower risk of IADL decline (OR = 0.37, 95% CI = 0.18–0.77). The results of additional stratified analyses by self-rated health, depression, and cognitive functioning showed that the associations of the type and frequency of SP with IADL decline varied according to physical and mental functioning. Conclusions Several types of SP have a favorable effect on IADL through moderate participation rather than frequent participation, and women with moderate participation in volunteer groups have a more beneficial effect on IADL than women with frequent participation. When advising community-dwelling older adults on SP for IADL maintenance, health professionals may need to take into account plateau effects, gender differences, and physical and mental functioning.