ASSOCIATION OF BODY-MASS INDEX AND BODY-FAT DISTRIBUTION WITH RISK OFLUNG-CANCER IN OLDER WOMEN

Obesity has been associated with an increased risk of cancer at a numb er of sites. A notable exception appears to be lung cancer, for which several studies suggest a modest inverse association. However, cigaret te smoking is directly associated with lung cancer and inversely assoc iated with body mass index. To investigate the hypothesis that body ma ss index is associated with lung cancer independent of cigarette smoki ng, the authors analyzed data from a prospective cohort study of 41,83 7 Iowa women aged 55-69 years at baseline in 1986. In addition, they e xamined whether central adiposity (high waist/hip ratio) was associate d with lung cancer incidence. Through 1992 (6 years of follow-up), 233 cases of lung cancer were identified through the State Health Registr y of Iowa. The body mass index at several ages was calculated from sel f-reports of height at baseline and weights at ages 18, 30, 40, and 50 years and at baseline. Current and former smokers generally had lower mean body mass indices than did nonsmokers at all ages except 18 year s. Cases generally had lower body mass indices than did noncases at al l ages except 18 and 30 years but, among current smokers, cases had hi gher mean body mass indices than did noncases at all ages except basel ine, although the differences were not statistically significant. An a pparent positive association of a high waist/hip ratio with lung cance r in the total cohort was found to be primarily accounted for by a hig her waist/hip ratio in current and former smokers. When stratified by smoking status and adjusted for other risk factors, including age and pack-years of smoking, the body mass index at baseline, body mass inde x at age 50 years, and waist/hip ratio were not associated with lung c ancer. The results of multivariate analyses suggest that the inverse a ssociation of body mass index with lung cancer can be explained by smo king status and that the positive association of waist/hip ratio with lung cancer can be explained by pack-years of smoking.