title: Caregiving stress, endogenous sex steroid hormone levels, and breast cancer incidence.
abstract: Stress is hypothesized to be a risk factor for breast cancer. The authors examined associations of hours of, and self-reported levels of stress from, informal caregiving with prospective breast cancer incidence. Cross-sectional analyses of caregiving and endogenous sex steroid hormones were also conducted. In 1992 or 1996, 69,886 US women from the Nurses' Health Study, aged 46-71 years at baseline, answered questions on informal caregiving; 1,700 incident breast cancer cases accrued over follow-up to 2000. A subset of 665 postmenopausal women not taking exogenous hormones returned a blood sample in 1990. Numbers of hours of care provided to an ill adult or to a child were each summed and analyzed as 0 (reference), 1-14, and >/=15 per week. Cox proportional hazards models were used in prospective analyses and linear models in cross-sectional analyses. High numbers of caregiving hours and self-reported stress did not predict a higher incidence of breast cancer. However, compared with women providing no adult care, women providing >/=15 hours of adult care (median, 54) had significantly lower levels of estradiol (geometric mean, 9.21 pg/ml vs. 7.46 pg/ml (95% confidence interval: 6.36, 8.76)) and bioavailable estradiol (geometric mean, 1.86 pg/ml vs. 1.35 pg/ml (95% confidence interval: 1.00, 1.82)). Stress from caregiving did not appear to increase breast cancer risk.
authors.affiliation: Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. candyce.kroenke@channing.harvard.edu
authors.forename: Candyce H
authors.initials: CH
authors.lastname: Kroenke
authors.forename: Susan E
authors.initials: SE
authors.lastname: Hankinson
authors.forename: Eva S
authors.initials: ES
authors.lastname: Schernhammer
authors.forename: Graham A
authors.initials: GA
authors.lastname: Colditz
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawachi
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Holmes
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000097:blood / Q000453:epidemiology* / Q000523:psychology; D017028:Caregivers / Q000523:psychology*; D003430:Cross-Sectional Studies; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D015994:Incidence; D016014:Linear Models; D008137:Longitudinal Studies; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D013315:Stress, Psychological / Q000097:blood / Q000453:epidemiology* / Q000523:psychology
chemical_list: D012739:Gonadal Steroid Hormones