Timing of menarche and first full-term birth in relation to breast cancer risk.
Ages at menarche and first birth are established risk factors for breast cancer. The interval between these ages may also affect risk, since the breast is more susceptible to carcinogenic insults during this period than during the parous period. However, few investigators have studied this relation. Using logistic regression, the authors evaluated associations between the timing of reproductive events and breast cancer risk among 4,013 cases and 4,069 controls enrolled in a multicenter, population-based US case-control study of White and African-American women (1994-1998). For White, parous premenopausal and postmenopausal women, those who had an interval of > or =16 years between the ages of menarche and first birth had 1.5-fold (95% confidence interval (CI): 1.0, 2.2) and 1.4-fold (95% CI: 1.1, 1.8) increased risks of breast cancer, respectively, in comparison with those who had < or =5 years between these ages. Adjusting for age at first birth altered these risk estimates somewhat, to odds ratios of 1.5 (95% CI: 0.8, 2.9) and 1.0 (95% CI: 0.6, 1.5), respectively. These associations were stronger for lobular and hormone-receptor-positive tumors but were absent among premenopausal African-American women. The authors conclude that the interval between age at menarche and age at first birth is associated with the risk of hormonally sensitive types of breast cancer, particularly among White women.
Li
Christopher I
CI
Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA. cili@fhcrc.org
Malone
Kathleen E
KE
Daling
Janet R
JR
Potter
John D
JD
Bernstein
Leslie
L
Marchbanks
Polly A
PA
Strom
Brian L
BL
Simon
Michael S
MS
Press
Michael F
MF
Ursin
Giske
G
Burkman
Ronald T
RT
Folger
Suzanne G
SG
Norman
Sandra
S
McDonald
Jill A
JA
Spirtas
Robert
R
D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics; D016022:Case-Control Studies; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D008423:Maternal Age; D008572:Menarche; D008875:Middle Aged; D016017:Odds Ratio; D011247:Pregnancy; D044469:Racial Groups / Q000706:statistics & numerical data; D012307:Risk Factors; D012959:Socioeconomic Factors; D013997:Time Factors; D014481:United States / Q000453:epidemiology