(dailyRx News) It's hard to get a full eight hours of sleep each night. But it's important. For women with breast cancer, it's extremely important.
A recent study has found that insufficient sleep is linked to more aggressive breast cancer.
Not getting enough sleep was also linked to a higher risk of breast cancer returning.
The study, led by Cheryl Thompson, PhD, from the Department of Family Medicine and Community Health at Case Comprehensive Cancer Center within Case Western Reserve University, analyzed women's OncotypeDX scores.
The OncotypeDX is a diagnostic lab test given to women who are able to have chemotherapy and have certain types of early-stage, estrogen receptor-positive breast cancer to help them decide their best treatment options.
However, it also provides information in predicting how likely it is that the women's breast cancer will return.
The researchers looked at the medical records of 101 women who had OncotypeDX scores on file for a different study.
The women were asked how many hours of sleep they typically got each night during the two years before they were diagnosed.
The found that OncotypeDX scores indicating that the women's breast cancer was likely to return were linked to the women's average sleep duration before they were diagnosed if the women were past menopause.
The less amount of sleep the women got previously, the higher their recurrence score was, making it more likely their cancer would return.
The recurrence score is based on the activity seen in a combination of 21 different genes.
Women who got six hours of sleep or less on average each night before they were diagnosed with breast cancer had higher scores.
The link between too little sleep and a higher risk of breast cancer recurrence was not seen in women who had not yet reached menopause.
The connection also remained after the researchers took into account the post-menopausal women's age, physical activity and weight as well as whether they smoked.
"This is the first study to suggest that women who routinely sleep fewer hours may develop more aggressive breast cancers compared with women who sleep longer hours," the researchers wrote. "More research will need to be done to verify this finding and understand the causes of this association."
The link did not greatly surprise William Kohler, MD, the director of the Florida Sleep Institute in Spring Hill, Florida.
"There are other previous studies that have shown that people who are sleep-deprived because of shift work are at an increased risk for certain cancer," Dr. Kohler said.
He pointed out that this study would have been stronger if the average sleep time had been prospectively measured instead of asking the women to recall their typical sleep. But the study still adds to our knowledge of ways that poor sleep can affect health.
"It's very important that we continue to gather information on the meaning of both the quality and quantity of sleep we get," he said.
The study was published in the August issue of Breast Cancer Research and Treatment. The study was funded by the National Cancer Institute and the Case Comprehensive Cancer Center. The authors declared no conflicts of interest.