SLEEP DURATION AND MORTALITY IN ADVANCED CANCER PATIENTS

NEW YORK (Reuters Health) - Sleep duration shows a U-shaped relationship with mortality in advanced cancer patients, with both short and long duration associated with increased mortality.

“Prior research has shown that sleep problems contribute to the development of depression in some individuals while other studies show that sleep problems are a result of depression,” said Dr. Jennifer L. Steel from the University of Pittsburgh in Pennsylvania.

“In this study, both sleep duration and depression independently predicted survival in patients diagnosed with cancer, and only short sleep was associated with increased risk of depression,” she told Reuters Health by email.

Short sleep duration and insomnia are associated with mortality in the general population and among chronically ill individuals, but the link between sleep problems and mortality in cancer patients remains poorly defined.

For their analysis, Dr. Steel’s team used data from 292 participants with cancer affecting the hepatobiliary-pancreatic system in two prospective studies.

Patients averaged 6.5 hours of sleep per night and took an average 29.9 minutes to fall asleep. Average sleep efficiency was 79.9%, with 53% of patients reporting sleep efficiency below 85%.

More than half the patients (54.1%) reported clinical depression, and these patients slept an average of 0.5 hour less per night than patients without depressive symptoms, the researchers report in Sleep Medicine, online January 20.

Sleep duration was independently associated with mortality, whereas sleep latency, sleep efficiency, and sleep disturbances were not significantly related to mortality.

After adjusting for other factors, including depression, there was a curvilinear relationship between sleep duration and mortality, with a significantly increased hazard for patients with short or long sleep duration.

“The importance of sleep should not be underestimated,” Dr. Steel said. “In the hospital setting, improving patients’ sleep is recommended (e.g., fewer interruptions during the night) to improve recovery from illness and prevent the development of chronic sleep problems.”

“In the outpatient setting, physicians should screen the patients for sleep problems and refer them for treatment if the patients report problems with their sleep,” she said. “Due to the limited number of sleep experts, innovative treatments for sleep are being developed that may be delivered through the Internet. However, if sleep problems remain resistant to treatment, a referral to a health psychologist or sleep disorders center is recommended.”

Dr. Steel emphasized that “identifying and treating sleep problems in patients diagnosed with cancer will improve quality of life as well as potentially increase survival of patients diagnosed with cancer. We currently have under review a paper concerning the underlying biological mechanisms linking sleep duration and mortality. At our center, we plan to screen and test the efficacy of a sleep intervention in our outpatient oncology clinic.”

Dr. Daehee Kang, an expert in cancer biomarkers at Seoul National University College of Medicine in South Korea, told Reuters Health by email, “Sleep is crucial in regulating the body’s immune system as well as maintaining the overall metabolic homeostasis. Therefore, it is critical to promote healthy sleeping habits (i.e., appropriate sleep duration, lower sleep disturbances, latency, and daytime dysfunction, greater sleep efficiency, etc.) when administering cancer treatments.”

“Sleep is not only a good health indicator but also a good indicator of other stressors an individual may be going through,” said Dr. Kang, who was not involved in the study.

He added, “When interpreting sleep study results, it is particularly important to note the age of the participants. Appropriate sleep duration varies among age group. As a side note, sleep studies are based on self-report of sleep duration, disturbances, etc. Therefore, recall bias may skew the accuracy of reported sleep measurements.”

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