Correlates of active and passive smoking in the California Teachers Study cohort.

OBJECTIVES: These analyses were designed to describe characteristics associated with active and passive smoking in a large cohort of women in order to identify possible confounders of the relationship between smoking exposures and breast cancer risk.
METHODS: Analyses were based on 1995 data collected from the California Teachers Study (CTS) and were restricted to those with complete and usable tobacco data (n = 128,174). Age-adjusted and race-adjusted odds ratios (OR) were generated by unconditional logistic regression.
RESULTS: Compared with never smokers, both current and former smokers experienced menarche at an earlier age. Current and former smokers also were more likely than their never smoking counterparts to be nulliparous. Among parous women, current, but not former smokers were less likely than never smokers to have had their first child at an older age. Similarly, among never smokers, those exposed to household passive smoking experienced menarche at an earlier age, were more likely to be nulliparous, and among parous women, were less likely to have had their first child at an older age than never smokers not exposed to passive smoking. Greater alcohol consumption was strongly associated with both active and passive smoking exposures. Compared with never smokers, current smokers were less likely to take antioxidant supplements, whereas former smokers were more likely to take antioxidant supplements. Among never smokers, antioxidant use did not differ depending on passive smoking exposure. A number of other dietary correlates of active and passive smoking were identified.
CONCLUSIONS: We identified a number of reproductive and dietary correlates to smoking exposures that underscore the need to adjust for such factors in an analysis of smoking and breast cancer and potentially other disease entities. Furthermore, these findings may suggest potential mechanisms underlying an association between breast cancer and smoking.