Social Network Characteristics and Body Mass Index in an Elderly Korean Population

Lee, Won Joon; Youm, Yoosik; Rhee, Yumie; Park, Yeong-Ran; Chu, Sang Hui; Kim, Hyeon Chang

Social contacts can promote, discourage, and sanction attitudes and behaviors [27, 28] . Social contacts may influence participation in organized sports [29] , dieting [30] , and food choices [31] . A study has linked unhealthy weight-control behaviors among adolescent girls to the dieting behaviors of their peers [32] . We found that the men's BMI was more strongly associated with network structure, that is, network size and density, than communication frequency as an index of network activation. KSHAP data from a restricted rural area had a simpler network structure than the NSHAP data because the NS-HAP study population was a nationally representative sample [24] . Almost the entire KSHAP study population existed in three of the nine possible density and size groups. Therefore, it was difficult to discriminate statistically the effect of density from the association between social network structure and BMI, because network size and density were strongly correlated. We postulate a possible explanation for the association between network structure and the men's BMI. Dense personal networks provide reinforcement for prevailing norms and practices and can provide protection from outside sources of influence or risk [25] . The greater the density, the more likely a network is to be considered a cohesive community, a source of social support, and an effective transmitter [33] . By contrast, the women's BMI was more strongly associated with network activation such as communication frequency than network structure. In the women, education was prominently related with BMI among potential confounders, such that more advanced education correlated with lower BMI. The well-educated have a healthier lifestyle [34] . They are more likely to exercise, less likely to smoke, and more likely to drink moderately rather than abstain or drink heavily. It could be inferred that individual attributes such as education level may be most important in determining women's BMI. A previous study explained possible reasons for gender differences in factors associated with BMI [35] . Social contact among friends may be qualitatively different for the men and women in relation to how they af-