SOCIODEMOGRAPHIC CHARACTERISTICS, SMOKING, MEDICAL AND FAMILY HISTORY, AND BREAST-CANCER

The relationship between sociodemographic characteristics, lifestyle, family history of cancer, medical history, and reproductive factors an d breast cancer was investigated in a population-based case-control st udy of French Canadians in Montreal. In this study, a total of 414 Fre nch-Canadian cases and 429 age- and language-matched population contro ls were interviewed. Ever-married women showed significantly lower ris k (OR: 0.64 [0.45-0.92]) for breast cancer, as did smokers (OR: 0.73 [ 0.55-0.98]), particularly of nonfilter cigarettes (OR: 0.36 [0.17-0.72 ]). Weight history, both for the year before the diagnosis of breast c ancer and 10 years previously, was associated with risk for the diseas e. A strong inverse relationship was found between the number of full- term pregnancies (OR: 0.48 [0.28-0.82]) and the risk of breast cancer, while the p trend for late age at first pregnancy (p = 0.02) and meno pause (p = 0.004) was statistically significant. A history of breast p roblems (OR: 1.87 [1.34-2.60]) and a history of breast cancer in relat ives (OR: 2.95 [1.63-5.34]) were strongly associated with risk. This s tudy confirms the risk factors of late age at first full-term pregnanc y, nulliparity, late age at menopause, and positive family history of breast cancer in the etiology of this disease. Perhaps the protective effect of smoking against breast cancer could be due to its antiestrog enic influence.