Lots of Sleep Tied to Worse Breast Cancer Survival Odds, Study Finds

Women with breast cancer who sleep at least nine hours a night may be more likely to die from their tumors than patients who get just eight hours of rest, a recent study suggests.

Compared to women sleeping eight hours a night, women who slept at least nine hours were 46% more likely to die of breast cancer, the study found. After up to 30 years of follow-up, the women who got more sleep were also 34% more likely to die of other causes, Reuters reports.

“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,” said lead study author Claudia Trudel-Fitzgerald of the Harvard T.H. Chan School of Public Health in Boston.

“Given that long sleep duration has been associated with mortality among cancer-free individuals, as well as among breast cancer patients in recent studies including ours, it is possible that the relationship of sleep duration with survival also exists for other types of cancer,” Trudel-Fitzgerald said by email. “However, further research is warranted.”

For the study, researchers examined data on post-diagnosis sleep duration for 3,682 women with breast cancer. They also examined pre-diagnosis sleep duration in a subset of 1,949 women and post-diagnosis sleep difficulties in a subset of 1,353 women.

During the study, there were 976 deaths, including 412 caused by breast cancer, researchers report in the British Journal of Cancer.

For the group of patients who had data on sleep difficulties, researchers found women who regularly struggled to fall or stay asleep were 49% more likely to die from all causes than women who rarely or never had these issues.

“People who are sicker are more likely to be fatigued from their illness, be it breast cancer or other cause, and thus sleep more,” said Cheryl Thompson, a researcher at Case Western Reserve University in Cleveland, Ohio.

Patients who reported getting more than nine hours of sleep were also more likely to be obese and have more advanced cancer.

Some patients might sleep more because they get less physical activity, spend more time in bed, or experience more social isolation or depression, said Kristen Knutson, a researcher at the Center for Circadian and Sleep Medicine at Northwestern University’s Feinberg School of Medicine in Chicago.

When patients do notice changes in how long or how well they sleep, it is worth discussing with their doctor, Knutson said.