Social ties and risk for cancer - a prospective cohort study

Background. Poor social support and small social networks have been associated with increased risks for conditions such as coronary heart disease as well as with overall mortality. We investigated the association between social ties and risk for cancer. Material and methods. The study sample consisted of 8 548 Danes who had been examined in 1991-1994 within the Copenhagen City Heart Study. The median length of follow-up was 9.3 years (range, 0-11.2 years). Social ties were measured from answers to a questionnaire on social networks. Regression analyses for cancers at the most frequent sites (breast, lung, prostate and colon and rectum) were conducted with the Cox proportional hazards model, with adjustment for a number of well-known risk factors for cancer. Results. While we found no significant association between social ties and risk for cancer in men, women with high social network scores had an increased risk for lung cancer of borderline significance (HR, 2.16; 95% CI, 1.02-4.60). The risks for breast cancer and colorectal cancers were not significantly increased in the same group of women. Discussion. The results of this study do not support the hypothesis that social network size is associated with a decreased risk for cancer.