Person:

Schernhammer, Eva

Introduction: Previous studies showed that higher testosterone levels are associated with greater risk of breast cancer in premenopausal women, but the literature is scant and inconsistent. Methods: In a prospective nested case-control study of 104 premenopausal women with incident breast cancer and 225 matched controls, all characterized by regular menstrual cycles throughout their lifetime, we measured the concentration of estradiol, total and free testosterone (FT), progesterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in blood samples collected on days 20 through 24 of their cycles. Results: In logistic regression models, the multivariate odds ratios (ORs) of invasive breast cancer for women in the highest tertile of circulating FT compared with the lowest was 2.43 (95% confidence interval (95% CI), 1.15 to 5.10; Ptrend = 0.03), whereas for total testosterone, the association had the same direction but was not statistically significant (OR, 1.27; 95% CI, 0.62 to 2.61; Ptrend = 0.51). Endogenous progesterone was not statistically associated with breast cancer (OR, 1.16; 95% CI, 0.60 to 2.27; Ptrend = 0.75), nor were the other considered hormones. Conclusions: Consistent with previous prospective studies in premenopausal women and our own earlier investigation, we observed that higher levels of FT are positively associated with breast cancer risk in women with regular menstrual cycles throughout their lifetimes. No evidence of risk was found associated with the other endogenous sex steroids.

Background: Breast cancer is a leading cause of cancer death in women. Sleep has been linked with mortality among cancer-free population; however, its association with survival among women with breast cancer is understudied. Methods: Breast cancer patients (N=3682) reported their average sleep duration post diagnosis. Subsamples also provided their pre-diagnosis sleep duration (n=1949) and post-diagnosis sleep difficulties (n=1353). Multivariate Cox models estimated hazard ratios (HR) and confidence intervals (CI) of all-cause, breast cancer, and non-breast cancer mortality. Results: At diagnosis, the mean age was 64.9 years and 91.7% were stage I or II. Women sleeping ⩾9 h per night post diagnosis had a strong higher risk of all-cause (multivariate HRs: MV-HR=1.37, CI=1.10–1.71), breast cancer (MV-HR=1.46, CI=1.02–2.07), and non-breast cancer mortality (MV-HR=1.34, CI=1.01–1.79), compared to women sleeping 8 h per night. Increased sleep duration post diagnosis (vs unchanged) and regular sleep difficulties (vs rare/none) were associated with a strong elevated risk of all-cause mortality (MV-HRincreased duration=1.35, CI=1.04–1.74; MV-HRregular difficulties=1.49, CI=1.02–2.19) and a moderate greater risk of breast cancer and non-breast cancer mortality. Conclusions: Various facets of sleep were associated with higher all-cause mortality risk. If replicated, these findings support evaluation of breast cancer patients' sleep duration and difficulties to identify those at risk for poorer outcomes.