Is Neighbourhood Linking Social Capital Associated With Colorectal Cancer Incidence and Mortality? A National Cohort Study From Sweden

Past research on the social determinants of colorectal cancer (CRC) has shown that lower socioeconomic status (SES) is associated with a higher risk of CRC. Similar to SES at the individual level, the neighbourhood social environment may partly affect the development of CRC. Although one important aspect of the neighbourhood social environment is social capital, no large-scale follow-up study has examined its potential effect on CRC. We examined whether neighbourhood "linking social capital," which is established through social relationships and may enable individuals to gain health-promotional resources, is associated with the incidence of and mortality related to CRC, after adjusting for individual- and familial-level factors. This longitudinal study, conducted in Sweden, comprised over 2 million men and over 2 million women aged 25 years or older. The follow-up period started on January 1, 2002 and continued until first incidence of CRC, death due to CRC, death from any other cause, emigration, or the end of the study period on December 31, 2015. We identified over 20,000 CRC cases during the follow-up period. We used multilevel logistic regression models to calculate odds ratios (ORs) with 95% confidence intervals. After adjustment for potential confounding factors, higher ORs of CRC were observed in individuals who lived in neighbourhoods with low, relative to high social capital. Our results suggest that neighbourhood linking social capital has independent effects on CRC. Future studies could explore how simple interventions that can build linking social capital can enhance people's health.