Cigarette smoking and breast cancer.

Abstract

To investigate cigarette smoking in relation to the risk of breast cancer. Interviews with women referred for mammography. Hjørring District Hospital, a public, population based hospital in Denmark. 3240 women aged 15-92 years referred for mammography during 1 June 1989 to 1 November 1991. Smoking, parity, age, reason for referral, breast cancer. In a multiple logistic regression analysis adjusted for six variables a pronounced increased risk of breast cancer was found in women who had smoked for over 20 years, and this was significant in women who had smoked for over 30 years (odds ratio 1.6, 95% confidence interval 1.1 to 2.3). The median age of women with breast cancer was 59 (range 31-81) years for smokers and 67 (38-92) years for nonsmokers. The difference of eight years between the median ages was significant (P < 0.01). Smoking may increase the risk of breast cancer after 30 years of smoking.