A new study reports that sleep efficiency, a ratio of time asleep to time spent in bed, is predictive of survival time for women with advanced breast cancer.
Results show that higher sleep efficiency was significantly associated with lower mortality over the ensuing six years, an effect that remained after adjusting for baseline prognostic factors such as age, estrogen receptor status and treatments received. Mean survival was 68.9 months for efficient sleepers compared with 33.2 months for participants with poor sleep efficiency. Further analysis found that a 10 percent increase in sleep efficiency reduced the estimated hazard of subsequent mortality by 32 percent. There was no association between sleep duration and survival.
“We were surprised by the magnitude of the relationship between sleep quality and overall survival even after we accounted for medical and psychological variables that typically predict survival,†said lead author Oxana Palesh, PhD, assistant professor in the Department of Psychiatry and Behavioral Sciences at Stanford University and research director of the Stanford Cancer Survivorship. “Good sleep seems to have a strongly protective effect, even with advanced breast cancer.â€
Study results are published in the May 1 issue of the journal Sleep.
The study involved 97 women with advanced breast cancer who had a mean age of 55 years. Objective sleep parameters were measured by wrist actigraphy for three consecutive days. Overall, participants spent about eight hours in bed at night but slept for only about 6.5 hours.
“This study emphasizes the importance of assessing sleep quality among women with breast cancer,†said American Academy of Sleep Medicine President Dr. M. Safwan Badr. “Healthy sleep is critical for physical health, quality of life and overall well-being.â€