Adolescence and breast carcinoma risk

BACKGROUND. Breast carcinoma risk may be modified by early life factors, in cluding physical growth and development, diet, and life-style factors of pr eadolescence and adolescence, as well as genetic factors. METHODS. The authors tested their hypothesis that adolescent growth and dev elopment are related to breast carcinoma incidence by evaluating 65,140 wom en who participated in the Nurses' Health Study. During 16 years of follow- up, 806 women were diagnosed with breast carcinoma prior to menopause, and another 1485 were diagnosed after menopause. Because adolescent growth was not directly observed in this cohort, the peak height growth velocity for e ach participant was estimated by using a model from another longitudinal st udy. Finally, Cox proportional hazards regression models were used to study associations between breast carcinoma incidence and adolescent factors in the Nurses' Health Study. RESULTS. Later menarche (relative risk [RR] = 0.52 for > 15 vs. less than o r equal to 11 years) and more body fatness at age 10 years (RR = 0.60 for f attest vs, leanest) were associated with a decreased risk of premenopausal breast carcinoma. The risk of postmenopausal breast carcinoma was lower for girls with later menarche (RR = 0.80), more body fat at age 10 years (RR = 0.72), and shorter adult height (RR = 1.29 for greater than or equal to 61 vs. less than or equal to 62 inches). Higher peak height growth velocity, derived from these 3 variables, was associated with increased risk of both premenopausal (RR = 1.31 for highest vs. lowest quintile) and postmenopausa l (RR = 1.40) breast carcinoma. These analyses controlled for birth cohort, other possible risk factors from the adolescent period, and family history . These associations persisted after controlling for age at the birth of a first child, parity, adult adiposity, and age at menopause. Post-hoc analys es suggested that, although childhood body fatness was associated with lowe r risk, increasing body fatness between ages 10 and 20 years was not protec tive against either premenopausal or postmenopausal breast carcinoma. CONCLUSIONS. Earlier menarche, extremely lean body mass at age 10 years, an d taller adult height were predictive of elevated breast carcinoma risk. Th e same three factors were also predictive of higher peak growth velocities during adolescence, lending credence to the hypothesis that more rapid adol escent growth may increase the risk of breast carcinoma development. Cancer 1999;85:2400-9. (C) 1999 American Cancer Society.