Social networks and mortality based on the Komo-Ise cohort study in Japan.
BACKGROUND
No prospective studies have examined the association between social networks and all-cause and cause-specific mortality among middle-aged Japanese. The study of varied populations may contribute to clarifying the robustness of the observed effects of social networks and extend their generalizability.


METHODS
To clarify the association between social networks and mortality among middle-aged and elderly Japanese, a community-based prospective study, the Komo-Ise Study, was conducted in two areas of Gunma Prefecture, Japan. A total of 11 565 subjects aged 40-69 years at baseline in 1993 completed a self-administered questionnaire. During the 7-year follow-up period, 335 men and 155 women died and the relative risk (RR) of each social network item was estimated by the Cox proportional hazard model.


RESULTS
Single women had significantly increased risks of all-cause (multivariate RR = 2.2), and all circulatory system disease (age-area adjusted RR = 2.6) mortality. Men who did not participate in hobbies, club activities, or community groups had significantly higher multivariate RR for all-cause (RR = 1.5), all circulatory system disease (RR = 1.6) and non-cancer and non-circulatory system disease (RR = 2.3) mortality. Urban women who rarely or never met close relatives had significantly elevated risks of all-cause (RR = 2.4), all cancer (RR = 2.6), and non-cancer and non-circulatory system disease (RR = 2.7) mortality after adjustment for established risk factors.


CONCLUSIONS
This study provides evidence that social networks are an important predictor of mortality risk for middle-aged and elderly Japanese men and women. Lack of participation, for men, and being single and lack of meeting close relatives, for women, were independent risk factors for mortality.
Iwasaki
Motoki
M
Department of Public Health, Gunma University School of Medicine, Japan. Present address: Epidemiology & Biostatistics Division, National Cancer Center Research Institute East, Chiba, Japan. moiwasak@east.ncc.go.jp
Otani
Tetsuya
T
Sunaga
Rumiko
R
Miyazaki
Hiroko
H
Xiao
Liu
L
Wang
Naren
N
Yosiaki
Sasazawa
S
Suzuki
Shosuke
S
D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000401:mortality; D002423:Cause of Death; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D017533:Marital Status; D008875:Middle Aged; D009026:Mortality; D009369:Neoplasms / Q000401:mortality; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D012944:Social Support; D011795:Surveys and Questionnaires