Women with breast cancer who get at least nine hours of sleep per night may have worse survival rates than patients who get eight hours of sleep, according to a new study by researchers from Harvard T.H. Chan School of Public Health and colleagues. They found that the longer sleepers were 46% more likely to die of breast cancer during the study period, and 34% more likely to die of other causes, compared to the shorter sleepers.
The study was published online March 30, 2017, in the British Journal of Cancer.
The researchers analyzed health data from 3,682 women participating in the Nurses’ Health Study for up to 30 years, who self-reported their sleep schedules. The study population did not include women in the most severe stage of cancer progression.
As this is an observational study, the researchers wrote, it is impossible to conclude whether sleep duration is causally related to future mortality risk in breast cancer patients. They note that declining health may foster longer sleep. However, they did find that the results were largely unchanged when they factored reverse causation into the analysis, lowering the likelihood that it is an issue.
Lead author Claudia Trudel-Fitzgerald, a research fellow in the Department of Social and Behavioral Sciences, told Reuters, “Sleep duration, but also changes in sleep duration before versus after diagnosis, as well as regular difficulties to fall or to stay asleep, may also be associated with mortality among women with breast cancer.”
Read Reuters article: Lots of sleep tied to worse breast cancer survival odds