Social support is important for the health of elderly populations. However, its longitudinal effect on incident dementia is unclear. We used the Aichi Gerontological Evaluation Study (AGES) project data to investigate the longitudinal effect of social support on dementia onset. Functionally independent older people at baseline (n = 14,088) in 10 municipalities were followed from 2003 to 2013 using National Long-term Care Insurance System data. Social support was assessed by the following support sources: co-residing family, family or relatives living apart, and friends or neighbors. Cumulative incidence of dementia was 14.6% and 18.7% for men and women, respectively. Cox proportional hazard models were employed by gender to investigate the association between social support and dementia onset adjusting for age, health status, health behaviors, subjective cognitive complaints, depression, and other socioeconomic factors. Gender differences were observed in the association between social support and incident dementia. Support from co-residing family members was protective among men, whereas among women, no effect of social support on dementia was observed. Among other social factors, community engagement was protective for women, while for men, being married was associated with lower incidence of dementia. The association between social support and dementia seems to differ by gender. When we design programs to promote social interactions among the elderly, we need to take into account such gender differences.
Keywords: dementia; longitudinal study; social support.