Association between Social Activity and Skeletal Muscle Mass (Japanese)

Because frailty in older adults is a strong risk factor for functional disability, early intervention for individuals who are at-risk of becoming frailty is important in preventing them from becoming bedridden and dying. Sarcopenia, a complex phenotype defined by loss of muscle mass, weak muscle strength, and decreased physical performance, is the primary cause of frailty. Typical risk factors for sarcopenia identified to date include aging, low body weight, malnutrition, and reduced daily activity. In addition, decreased social activity may also be a risk factor for sarcopenia, although few studies have examined the association between them. In this study, we aimed to investigate the possible involvement of social activity in sarcopenia in a community-dwelling of older adults. A total of 2,212 participants of the Nagahama study, a longitudinal study based on community residents living in the Nagahama City, Shiga Prefecture, Japan, was included in the analysis. Social activity was queried using a structured questionnaire. The skeletal muscle mass index (SMI) measured using bioimpedance analysis was used as an index of skeletal muscle mass. The mean age of the study participants was 71.0 ± 4.1 years, and 43.0% were male. SMI was significantly lower in women, and positively correlated with body mass index in both sexes. Individuals who had been engaged in agriculture, forestry, or fisheries had significantly higher SMI independently of age and body mass index. The degree of neighborliness was also significantly related to SMI, with significantly lower SMI for those who had limited or infrequent neighborhood contacts. In addition, SMI was higher in individuals who engaged in frequent social activities, such as community activities, sports/hobbies/recreational activities, and volunteer/non-profit organizations/civic activities. This paper concludes that higher social activity is a protective factor for the development of sarcopenia.