Abstract A57: Body mass index in relation to incident lung cancer in African American women

A number of studies have found that obesity, as measured by body mass index (BMI), is inversely related to lung cancer incidence among current and former smokers. The findings may be due to uncontrolled confounding by cigarette smoking, as smokers tend to be thinner on average than non-smokers and have a greatly increased risk of lung cancer. Recent results from the NIH-AARP Diet and Health Study, with a very large sample size, suggest that the observed association may be independent of smoking effects. The study also found the association to be stronger among women than men. Limited data are available on the relation of BMI to lung cancer incidence in African Americans. We assessed this question in the Black Women's Health Study, an ongoing prospective follow-up of 59,000 women from all regions of the U.S. Participants enrolled in the study by completing mailed questionnaires in 1995 and have been followed by biennial questionnaire since then. Self-reported weight and height at baseline were used to calculate BMI (weight in kilograms divided by height in meters2). Detailed information on cigarette smoking was ascertained on each questionnaire. Incident cases of lung cancer were ascertained by study questionnaire, cancer registry, or National Death Index. Pathology reports and/or cancer registry data were reviewed by a study oncologist to identify primary cancers. Cox proportional hazard models were used to estimate hazard ratios for the association of various levels of BMI relative to BMI 18.5-24.9 (“lean” women) in relation to lung cancer incidence. Multivariate models included adjustment for pack-years of cigarette smoking and current smoking status, as well as other variables. Among 331 incident primary lung cancer cases that occurred from 1995 to 2011, cigarette smoking, as measured by pack-years, cigarettes per day, or age started smoking, was strongly associated with increased risk of lung cancer, as expected. Baseline BMI was inversely associated with lung cancer risk: the hazard ratio for obese women (BMI ≥30) relative to lean women was 0.74 (95% confidence interval (CI) 0.55-0.99). In analyses stratified by smoking status, the HR for obese women relative to lean women was 0.60 (0.37-0.97) among current smokers, 0.88 (0.55-1.39) among former smokers, and 0.86 (95% CI 0.43-1.73) among never smokers. Of note, controlling for pack-years or age started smoking had little effect on the hazard ratios among current and former smokers. Our results suggest that obesity may be associated with a lower risk of lung cancer. These findings, from a study of African American women, confirm recent findings from the predominantly Caucasian NIH-AARP Study. Residual confounding by cigarette smoking did not appear to explain the association. Potential mechanisms will be discussed. Citation Format: Traci N. Bethea, Lynn Rosenberg, Marjory Charlot, Lucille L. Adams-Campbell, Julie R. Palmer. Body mass index in relation to incident lung cancer in African American women. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr A57.