If you are at risk of breast cancer, make a good night's sleep part of your routine. That, researchers say, will improve your odds of avoiding the disease.
The team of researchers at Case Western Reserve University say their findings are the first to show an association between insufficient sleep and biologically more aggressive tumors as well as likelihood of cancer recurrence.
The researchers analyzed medical records and survey responses from 412 post-menopausal breast cancer patients treated at University Hospital Case Medical Center with Oncotype DX, a widely utilized test to guide treatment in early stage breast cancer by predicting likelihood of recurrence.
Six hours or less not enough
The patients were recruited at diagnosis and asked about the average amount of sleep they had gotten in the last two years. Researchers found that women who reported six hours or less of sleep per night on average before breast cancer diagnosis had higher Oncotype DX tumor recurrence scores.
The Oncotype DX test assigns a tumor a recurrence score based on the expression level of a combination of 21 genes.
"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," said Dr. Cheryl Thompson, Assistant Professor at Case Western Reserve University School of Medicine and lead author. "We found a strong correlation between fewer hours of sleep per night and worse recurrence scores, specifically in post-menopausal breast cancer patients. This suggests that lack of sufficient sleep may cause more aggressive tumors, but more research will need to be done to verify this finding and understand the causes of this association."
Doesn't affect pre-menopausal women
The link between lack of sleep and aggressive cancer appeared only in post-menopausal women, the researchers said. They say that's not surprising since there are different mechanisms underlying pre-menopausal and post-menopausal breast cancers.
The data suggest that sleep may affect carcinogenic pathways specifically involved in the development of post-menopausal breast cancer, but not pre-menopausal cancer.
"Short sleep duration is a public health hazard leading not only to obesity, diabetes and heart disease, but also cancer," said Dr. Li Li, a study co-author. "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."