(CNN) - Older women who don't get enough sleep may be more at risk to more aggressive types of breast cancer, according to a study published in the journal Breast Cancer Research and Treatment.
According to Science Daily, the research team reviewed the medical records and surveys from more than 400 post-menopausal breast cancer patients.
Among the survey questions, researchers asked about the patients' sleep patterns and found women who got six hours of sleep or less each night had a higher recurrence of tumors.
They were unable to find a similar link in pre-menopausal women.
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