Obesity in relation to lung cancer incidence in African American women.

PURPOSE

Although a number of studies have found an inverse association between body mass index (BMI) and risk of lung cancer, there is little information on this relation in African Americans, who experience a higher incidence of lung cancer.

METHODS

We assessed the relation of BMI to incidence of lung cancer in the Black Women's Health Study, an ongoing prospective follow-up of 59,000 women in the USA. Cox proportional hazard models were used to estimate hazard ratios for various levels of BMI relative to BMI 18.5-24.9 kg/m2 ("normal weight") with adjustment for age, education, pack-years of smoking, and other covariates. Two other anthropometric measures, waist circumference (WC) and waist/hip ratio (WHR), were also assessed. A total of 323 primary lung cancer cases were identified from 1995 to 2011.

RESULTS

The hazard ratio (HR) for BMI ≥ 30 relative to BMI 18.5-24.9 was 0.69 (95% CI 0.51-0.92). As expected, cigarette smoking was strongly associated with increased risk of lung cancer. In analyses stratified by smoking status, the HR for BMI ≥ 30 relative to BMI 18.5-24.9 was 0.62 (0.38-1.00) among current smokers, 0.90 (0.56-1.42) among former smokers, and 0.83 (0.41-1.70) among never smokers (p for interaction = 0.28). Control for pack-years of smoking or age started smoking had little effect on the hazard ratios. WC and WHR were not materially associated with lung cancer risk.

CONCLUSION

Our results indicate that high BMI is associated with a lower risk of lung cancer in African American women, particularly among current smokers.