Sleeping more than nine hours a night results in an increased risk of death for women with breast cancer and a similar rise in other causes of death.
In a long-term study spanning more than 30 years, researchers from the Harvard T.H. Chan School of Public Health discovered that breast cancer patients who slept nine or more hours per night had a 46 percent greater chance of dying compared to women who slept eight hours or fewer.
Additionally, the researchers found that all-cause mortality — or death due to reasons other than breast cancer — spiked 34 percent among women who slept more than nine hours compared to their peers who slept less.
While previous studies have also found a link between longer hours in bed and all-cause mortality, the new study, appearing in the British Journal of Cancer, is the first to link excessive sleep and poor breast cancer outcomes.
“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,” study author Claudia Trudel-Fitzgerald of the Harvard T.H. Chan School of Public Health in Boston told Reuters.
“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 added.
Other Sleep Patterns Emerge
The new study adds further evidence to a growing body of medical literature tying excessive sleep to poor health outcomes.
“The increased mortality observed among long sleepers is consistent with recent meta-analyses that demonstrated an association between sleep duration, and all-cause and cardiovascular death in the general population,” report the authors in the British Journal of Cancer.
What’s exactly behind the association remains unclear, but the researchers believe excessive sleep may point to underlying conditions or other diagnoses at play.
“Various mechanisms of the long sleep duration-mortality relationship have been proposed, including sleep fragmentation, lack of physiological challenge (e.g., exercise), depression and underlying disease processes,” report the researchers.
In other words, getting more than nine hours of sleep may be an indication that something is amiss with a person’s health. The researchers also found that “an increase in sleep duration from pre- to post-diagnosis, compared to no change, was associated with a 35% higher risk of all-cause death.”
Furthermore, the numbers show that poor sleep patterns don’t convey better outcomes — women reporting frequent sleep difficulties had a 49 percent increased risk of all-cause mortality.
“One of the most commonly reported complaints in oncology is poor sleep quality, seen in up to 70% of non-metastatic breast cancer patients within the first months following diagnosis,” report the study authors. “Chronically poor sleep may influence cancer outcomes through impaired immune function.”
The study may offer the scientific community a new perspective in helping women deal with a challenging diagnosis, and may improve health outcomes and decrease mortality rates. The researchers suggest that “the mechanisms underscoring these associations should be explored. If these results are replicated in future work, it will be important to evaluate breast cancer patients for long and changing sleep duration, in addition to sleep difficulties in the clinical setting, to identify patients who may be at risk for poor outcomes.”