Risk of papillary thyroid cancer in women in relation to smoking and alcohol consumption

Both smoking and alcohol consumption may influence thyroid function, althou gh the nature of these relations is not well understood. We examined the in fluence of tobacco and alcohol use on risk of papillary thyroid cancer in a population-based case control study. Of 558 women with thyroid cancer diag nosed during 1988-1994 identified as eligible, 468 (83.9%) were interviewed ; this analysis was restricted to women with papillary histology (N = 410), Controls (N = 574) were identified by random digit dialing, with a respons e proportion of 73.6%. We used logistic regression to calculate odds ratios (OR) and associated confidence intervals (CI) estimating the relative risk of papillary thyroid cancer associated with cigarette smoking and alcohol consumption. A history of ever having smoked more than 100 cigarettes was a ssociated with a reduced risk of disease (OR = 0.7, 95% CI = 0.5-0.9). This reduction in risk was most evident in current: smokers (OR = 0.5, 95% CI = 0.4-0.7). Women who reported that they had ever consumed 12 or more alcoho l-containing drinks within a year were also at reduced risk (OR 0.7, 95% CI = 0.5-1.0). Similar to the association noted with smoking, the reduction i n risk was primarily present among current alcohol consumers. The associati ons we observed, if not due to chance, may be related to actions of cigaret te smoking and alcohol consumption that reduce thyroid cell proliferation t hrough effects on thyroid stimulating hormone, estrogen, or other mechanism s.