Social support and cancer incidence and mortality: the JPHC study cohort II

Studies conducted in Western countries have found a robust association between higher social support and improved cancer outcomes, particularly for breast cancer incidence and prognosis. However, less is known about the influence of social support on cancer among Asian populations where the measures of social support may differ in social relationships. In this prospective cohort study in Japan, we sought to examine the associations between the incidence and mortality of total and site-specific cancer. We examined prospectively the association between social support and risk of cancer incidence and mortality within a cohort of 44,152 Japanese men and women, aged 40-69 years, free of prior diagnosis of cancer and cardiovascular disease. Social support was measured by emotional support defined as receipt of confidant support and esteem support from family members or friends and by social isolation. A total of 3,444 cases of newly diagnosed cancer and 1,561 cancer deaths occurred between the baseline questionnaire (1993-1994) and the end of follow-up in January 2004. The multivariate hazard ratios (HR) and 95 % confidence intervals for colorectal cancer incidence and mortality in the highest social support versus lowest social support group were 1.48 (1.06-2.05) and 3.07 (1.65-5.69) in men, respectively. Social support was not associated with other site-specific cancer incidence or cancer outcomes in women. Low social support was associated with higher risk of both colorectal cancer incidence and mortality in men. Social support may affect colorectal cancer onset and prognosis via a range of factors, including healthier lifestyles as well as adherence to therapeutic regimens.