Impact of changing US cigarette smoking patterns on incident cancer: risks of 20 smoking-related cancers among the women and men of the NIH-AARP cohort.

Background: Historically, US women started smoking at a later age than men and had lower relative risks for smoking-related cancers. However, more recent birth cohorts of women and men have similar smoking histories and have now reached the high-risk age for cancer. The impact of these changes on cancer incidence has not been systematically examined.

Methods: Relative risks (RR), 95% confidence intervals (CI) and attributable fractions were calculated for cigarette smoking and incidence of 20 smoking-related cancers in 186 057 women and 266 074 men of the National Institutes of Health-AARP cohort, aged 50 to 71 years in 1995 and followed for 11 years.

Results: In the cohort, which included participants born between 1924 and 1945, most women and men started smoking as teenagers. RRs for current vs never smoking were similar in women and men for the following cancers: lung squamous-cell (RR women: 121.4, 95% CI: 57.3-257.4; RR men:114.6, 95% CI: 61.2-214.4), lung adenocarcinoma (RR women: 11.7, 95% CI: 9.8-14.0; RR men: 15.6, 95% CI: 12.5-19.6), laryngeal (RR women: 37.0, 95% CI: 14.9-92.3; RR men: 13.8, 95% CI: 9.3-20.2), oral cavity-pharyngeal (RR women:4.4, 95% CI: 3.3-6.0; RR men: 3.8, 95% CI: 3.0-4.7), oesophageal squamous cell (RR women: 7.3, 95% CI: 3.5-15.5; RR men: 6.2, 95% CI: 2.8-13.7), bladder (RR women: 4.7, 95% CI: 3.7-5.8; RR men: 4.0, 95% CI: 3.5-4.5), colon (RR women: 1.3, 95% CI: 1.2-1.5; RR men: 1.3, 95% CI: 1.1-1.4), and at other sites, with similar attributable fractions.

Conclusions: RRs for current smoking and incidence of many smoking-related cancers are now similar in US women and men, likely reflecting converging smoking patterns.