In a study published in May 2014 in the journal Sleep, the ratio of time sleeping versus the time spent in bed, aka a person's sleep efficiency, is predictive of survival time in women who have advanced breast cancer.
The study included 97 women with advanced breast cancer who's mean age was 55. The results show that higher sleep efficiency, meaning more time in bed spent sleeping versus trying to sleep, significantly impacted the patient's survival time. The mean survival time was 68.9 months for efficient sleepers whereas sleepers with poor efficiency had a mean of 33.2 months. While there was no association between how long a person slept and it's impact on their survival, further analysis found a 10 percent increase in sleep efficiency to reduce the estimated hazard of dying by 32 percent.
"We were surprised by the magnitude of the relationship between sleep quality and overall survival even after we accounted for medial and psychological variables that typically predict survival," Oxana Palesh, lead study author and assistant professor in the Department of Psychiatry and Behavioral Sciences at Stanford University, said in a statement. "Good sleep seems to have a strongly protective effect, even with advanced breast cancer."Whizzco