CYP19A1 and breast cancer: Initial results found some evidence for a per category increase in daytime-sleepiness reducing overall breast cancer mortality (HR = 0.34, 95% CI = 0.14, 0.80), and for insomnia symptoms reducing odds of mortality in oestrogen receptor positive breast cancers not receiving chemotherapy (HR = 0.18, 95% CI = 0.05, 0.68) and in patients receiving aromatase inhibitors (HR = 0.23, 95% CI = 0.07, 0.78).