title: Early life factors in relation to breast cancer risk in postmenopausal women.
abstract: We evaluated the role of early life factors in a large, population-based, case-control study of breast cancer risk in postmenopausal women. Case women in Massachusetts, New Hampshire, and Wisconsin were ascertained through state cancer registries; control women were randomly selected from drivers license lists (50-65 years of age) or Medicare beneficiary lists (65-79 years of age). Information concerning factors of interest was obtained through structured telephone interviews. Overall, 83% of eligible cases and 78% of eligible controls participated, and data from more than 2900 women were available for this analysis. We observed a weak J-shaped relationship between birth weight and breast cancer risk; the increased risk was not statistically significant for either the lowest or the highest birth weight. Parental smoking during the pregnancy was not associated with risk of breast cancer in the adult daughter. Breast cancer risk increased significantly with father's education (P = 0.01). Risk also increased with greater age of the mother at the time of the subject's birth (P = 0.04). The subject's birth rank was inversely associated with risk (P = 0.03), as was the number of older sisters (P = 0.03), but the number of older brothers, number of younger siblings, sibship gender ratio, and total sibship size were unrelated to risk. Overall, our results are consistent with previous studies and suggest that these early life factors have a modest influence on breast cancer risk in postmenopausal women.
authors.affiliation: Norris Cotton Cancer Center and the Department of Community and Family Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, USA. Linda.Titus-Ernstoff@Dartmouth.edu
authors.forename: Linda
authors.initials: L
authors.lastname: Titus-Ernstoff
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Egan
authors.forename: Polly A
authors.initials: PA
authors.lastname: Newcomb
authors.forename: Jiao
authors.initials: J
authors.lastname: Ding
authors.forename: Amy
authors.initials: A
authors.lastname: Trentham-Dietz
authors.forename: E Robert
authors.initials: ER
authors.lastname: Greenberg
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Trichopoulos
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D017698:Postmenopause; D012307:Risk Factors; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology