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Study Finds New Risk Factor for Post-Menopausal Breast Cancer

insomnia, breast cancer, sleep deprivation, breast cancer risk

Lack of sleep may seem like just an annoyance that makes you tired and cranky, but chronically inadequate sleep time does carry several health risks. A new study finds this particularly distressing for older women – lack of sleep appears to increase the risk of more severe breast cancer.

It is estimated that 50 to 70 million adults in the United States have chronic sleep difficulties. Sleep deprivation can lead to accidents, impaired attention and memory, and depression. Lack of sleep also increases the risk for heart disease, high blood pressure, stroke, diabetes, and obesity.

In a first-of-its-kind study, Dr. Cheryl Thompson PhD and Dr. Li Li MD PhD of Case Western Reserve University School of Medicine analyzed medical records and survey responses from 412 post-menopausal breast cancer patients treated at UH Case Medical Center. All patients were recruited at diagnosis and asked about the average sleep duration for the past two years.

The women were given a widely utilized test called Oncotype DX which helps guide physicians in their treatment plans. It predicts the likelihood of cancer recurrence based on the expression level of a combination of 21 genes.

Women who reported sleeping less than 6 hours per night had a higher chance of recurring breast cancer. "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. We found a strong correlation between fewer hours of sleep per night and worse recurrence scores, specifically in post-menopausal breast cancer patients," said Dr. Thompson.

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The team did not find the same association in pre-menopausal breast cancer patients suggesting the mechanism of cancer development is different in women who had reached menopause.

More research is needed to verify the finding and to understand the cause of the association. As lack of sleep is associated with a greater risk for obesity, and obesity increases the likelihood of estrogen receptor-positive breast cancer, the link could be within this pathway. However, Dr. Thompson and Dr. Li did adjust their results to take weight, age, physical activity, and smoking status into consideration.

Obesity could also affect cancer recurrence as it hinders effective treatment, according to a 2009 study by the American Cancer Society.

Another recent study suggests that lack of sleep affects the immune system which could contribute to many diseases, possibly even cancer. But again, more research is needed to sort this out.

“Short sleep duration is a public health hazard leading not only to obesity, diabetes and heart disease, but also cancer," said Dr. Li. "Effective intervention to increase duration of sleep and improve quality of sleep could be an under-appreciated avenue for reducing the risk of developing more aggressive breast cancers and recurrence."

Journal Reference:
Cheryl L. Thompson and Li Li. Association of sleep duration and breast cancer OncotypeDX recurrence score. BREAST CANCER RESEARCH AND TREATMENT. Volume 134, Number 3 (2012), 1291-1295, DOI: 10.1007/s10549-012-2144-z