Community- and individual-level socioeconomic status and breast cancer risk: Multilevel modeling on Cape Cod, Massachusetts

BACKGROUND: Previous research demonstrated increased risk of breast cancer associated with hi gher socioeconomic status (SES) measured at both the individual and community levels. However, little attention has been paid to simultaneously examining both measures. OBJECTIVES: We evaluated the independent influences of individual and community SES on the risk of breast cancer using case-control data. Because our previous work suggests that associations may be stronger after including a latency period, we also assessed the effect of community-level SES assuming a 10-year latency period. METHODS: We obtained individual education for cases and matched controls diagnosed between 1987 and 1993 on Cape Cod, Massachusetts (USA). We acquired community-level SES from census data for 1980 and 1990. Using SES data at diagnosis and 10 years earlier, we constructed models for breast cancer risk using individual-level SES only, community-level SES only, and a multilevel analysis including both. We adjusted models for other individual-level risk factors. RESULTS: Women with the highest education were at greater risk of developing breast cancer both 1980 and 1990 [odds ratio (OR) = 1.17 and 1.19, respectively]. Similarly, women living in the highest-SES communities in 1990 had greater risk (OR = 1.30). Results were stronger in the analyses considering a latency period (OR = 1.69). Adjusting for intragroup, correlation had little effect on the analyses. CONCLUSIONS: Models including individual- or community-level measures of SES produced associations similar to those observed in previous research. Results for models including both measures are consistent with a contextual effect of SES on risk of breast cancer independent of individual SES.