Cigarettes and waterpipe use and risk of colorectal cancer in Iran: the IROPICAN study.

We aimed to investigate the association between cigarettes and waterpipe use and colorectal cancer (CRC) in an Iranian population. We analyzed data from a multicenter hospital-based case-control study in Iran (IROPICAN). Data on tobacco smoking, including cigarettes, and waterpipe smoking, were collected in detail. Multivariate logistic regressions estimated the odds ratios (ORs) and 95% confidence intervals (CIs) for the association between cigarette and waterpipe smoking and CRC, accounting for confounders including age, sex, socioeconomic status, opium use, marital status, family history of cancer, red meat, fiber, body shape at age 15 and perceived physical workload, and each other of the two exposures. The study population consisted of 3215 controls and 848 cases, including 455 colon and 393 rectum cancers. We found no association between CRC and cigarette smoking (OR, 0.8; 95% CI, 0.6-1.0) or waterpipe smoking (OR, 1.1; 95% CI, 0.9-1.5). Analysis by categories of cigarette pack-year and frequency of waterpipe smoking (head-year) did not show associations. We observed an inverse association between colon cancer and cigarette smoking (OR, 0.6; 95% CI, 0.5-0.9). There was, however, no significant association by pack-year categories. Cigarette and waterpipe smoking was not associated with CRC in the Iranian population. Further studies are needed to better understand the role of waterpipe on CRC.