Cigarette smoking and risk of breast cancer: a prospective study of 24,329 Norwegian women.
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.
Vatten
L J
LJ
Department of Oncology, University Hospital, Trondheim, Norway.
Kvinnsland
S
S
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*