It is a well-known fact that women with advanced breast cancer suffer from severe fatigue and poor sleep. In fact, a study published out of Stanford several years ago showed that 63% of women with metastatic breast cancer reported one or more types of sleep disturbances and 37% of them were using sleeping pills regularly. However, the question remained as to what impact this lack of sleep might have on the course of their disease.
In this month’s journal Sleep, a study of 97 participants gives us an answer. When examined over a period of six years, 74% had metastatic disease, 18% had locally advanced disease, and 7.2% either. At entrance, their sleep was evaluated using a technique called actigraphy. An actigraph is a device that detects and records arm movements using an accelerometer. Data from actigraphs are commonly used as a tool for assessment of sleep and wake. It is a motion detector, and the assumption is made that the person is asleep when there is little or no motion and awake when motion is detected.
Utilizing this tool the authors were able to track TST (total sleep time), SE (sleep efficiency), which is a measurement of the percent of time spent in bed actually asleep divided by total time in bed, and WASO (wake after sleep onset time), a measurement of how much time is spent awake after falling asleep. Their results are quite remarkable. They found the greatest predictors of shorter survival were SE below 85% and increased awakenings from sleep. Moreover, those women who had a greater than 85% SE survived an average of 68.9 months while those with less than 85% SE survived an average of 33.2 months. They also found that more awakenings from sleep also predicted a significant decrease in survival.
This is not the first study to point out the relationship of poor sleep quality to cancer. The causes are probably multifactorial. In some, it is due to associated anxiety and depression. In others the chemotherapy itself may be the culprit, while in others the development of sleep-preventing behaviors such as excessive napping, sleeping in late, or going to bed late may disrupt normal circadian rhythms. Finally, opioid medications used for pain management can decrease deep sleep and increase lighter stages of sleep.
So why should sleep affect cancer survival? The answer is probably to be found in the effects of sleep deprivation on the hormonal and immune systems. Prior studies have demonstrated that insufficient sleep can promote the production of tumor promoting inflammatory mediators called cytokines while inhibiting the production of other cytokines like interferon-gamma (IFN-gamma) which inhibit tumor growth. Other studies have demonstrated that insufficient sleep also causes abnormalities in cortisol production, which can be deleterious in dealing with the stress of cancer treatment.
What is the take home message? It is that in those of us fighting cancer we need to make sleep a priority. We should be encouraged by the fact that prior studies have demonstrated that CBT (cognitive behavioral therapy), when utilized effectively, can normalize these immune and hormonal abnormalities and for that reason increase survival. Therefore, if you are undergoing chemotherapy or battling cancer at any stage, you need to make sleep a priority. If you are unable to do this, talking with your health care provider is a priority.