In honor of October being Breast Cancer Awareness Month, let’s look at the connection between sleep and cancer. This is a complex issue, as getting poor sleep increases the risk of cancer, and sleep in cancer patients is disturbed. Let’s look at each situation more closely.
Poor Sleep Increases the Risk of Cancer
In the last ten years research has been done looking at the life-long sleep histories of breast cancer patients. It’s been found that being awake at night (usually for shift work) increases the risk of developing cancer. This is thought to be because the light suppresses melatonin, which is highest during the dark night. In turn, when melatonin is low estrogen levels are increased, thus increasing risk of breast cancer. Colo-rectal cancer is also increased in women who have done shift work for 15 years or more. In addition to melatonin, cortisol patterns are irregular when a person is not sleeping well. Cortisol is important for our immune system.
It’s not only shift workers who suffer increased risk of cancer. Among physically active women, those who sleep less than 7 hours per night have a 47% increased risk of cancer compared to those who sleep more.
Sleep in Cancer Patients is Disrupted
Cancer patients experience sleep problems at a high rate. About 30-50% have insomnia, which worsens with repeat courses of chemotherapy. They also experience irregular sleep-wake patterns.