6 Hours or Less of Sleep a Risk Factor for Aggressive Breast Cancer

Post-menopausal breast cancer patients who sleep 6 hours or less a night are at a higher risk of developing biologically aggressive breast cancers, reported researchers in the August 2012 issue of Breast Cancer Research and Treatment.

The findings are based on an analysis of medical records and survey responses from 412 post-menopausal breast cancer patients treated at University Hospitals Case Medical Center. The participants were recruited at diagnosis and questioned about their sleep patterns over the previous 2 years. The researchers also used an Oncotype DX breast cancer assay—a test that analyzes the expression of a panel of 21 genes in a tumor—to try to predict likelihood of cancer recurrence for each patient.

The researchers found that post-menopausal women who reported 6 hours or less of sleep on average before breast cancer diagnosis had higher Oncotype DX tumor recurrence scores. Despite these findings, there was no correlation found in pre-menopausal women, which the authors attribute to the different underlying mechanisms of pre-menopausal and post-menopausal breast cancers.

“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 lead author Cheryl Thompson, PhD, assistant professor at Case Western Reserve University School of Medicine.