title: Cigarette smoking and risk of breast cancer: a prospective study of 24,329 Norwegian women.
abstract: The association between cigarette smoking and incidence of breast cancer has been analyzed in 242 cases of breast cancer that developed among 24,329 Norwegian women over 11-14 years of follow-up. At baseline they were aged 35-51. There was no overall association between cigarette smoking and the risk of breast cancer. The age-adjusted incidence rate ratio (IRR) was unity (IRR = 1.04, 95% CI 0.76-1.42) for regular smokers (10 or more cigarettes daily) compared with non-smoking women. In women who reported smoking between 1 and 9 cigarettes per day there was an age-adjusted IRR of 1.28 (95% CI 0.95-1.73). The lack of association with cigarette smoking was replicated in subgroup analyses of women diagnosed before age 51 ("premenopausal") and among women diagnosed after this age ("postmenopausal"). However, there was a significant interaction between cigarette smoking, body mass index and age at diagnosis (P = 0.01), which might indicate that an interaction between cigarette smoking and body mass exerts differential effects on breast cancer risk in premenopausal and postmenopausal women.
authors: Department of Oncology, University Hospital, Trondheim, Norway.
authors: L J
authors: LJ
authors: Vatten
authors: S
authors: S
authors: Kvinnsland
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*