Poster Sessions

Epi-17

Neal Freedman

N. Freedman, M. Leitzmann, A. Hollenbeck, A. Schatzkin, C. Abnet

Cigarette smoking and subsequent risk of lung carcinoma in men and women.

Background: Lung cancer is the leading cause of cancer related mortality worldwide. Several provocative reports have suggested that women are more susceptible to the carcinogens in cigarette smoke than men and that incidence rates in never smoking women are higher than in never smoking men. These results for smokers are controversial. Large studies that present both relative and absolute risks are needed to resolve this controversy. But, few studies have directly compared absolute and relative risks by smoking use in a single population, or examined differences by histologic type. Data on the incidence rates of lung cancer in never smoking men and women, which serve as the referent group for relative risk calculations, are particularly sparse. Methods: We prospectively examined the association between cigarette smoking and lung carcinoma in 283,678 men and 192,522 women of the National Institutes of Health–AARP cohort who were 50 to 71 years old at enrollment in 1995–1996. We compared the age-standardized incidence rates of lung carcinoma by self-reported smoking status in men and women and calculated hazard ratios adjusted for age, body mass index, education, and intakes of alcohol, fruits, vegetables, and meats to estimate the relative increase in the risk of lung carcinoma caused by smoking. We examined both total lung carcinoma and individual histologic types. Results: During follow-up, lung carcinomas occurred in 4,132 men and 2,286 women. Incidence rates were similar in never smoking men (140 cases: 22.7 per 100,000 person-years, 95% confidence interval (CI): 19.0-26.5) and never smoking women (167 cases: 25.7, 95% CI: 21.8-29.6). Likewise, among smokers, we found similar incidence rates in men and women with comparable smoking histories. Relative to never smokers, the hazard ratio for current smokers of more than 2 packs per day was 48.4 (95% CI: 37.9-61.8) in men and 44.4 (95% CI: 32.1-61.6) in women. Hazard ratios associated with cigarette smoking did not significantly differ between men and women for adenocarcinoma, small cell, squamous, or undifferentiated histologic types. Conclusions: In the largest prospective study of cigarette smoking and lung carcinoma risk to date (6,418 incident cases), never smoking men and never smoking women had similar rates of lung carcinoma and men and women were equally susceptible to the carcinogenic effects of cigarette smoking.