A new study has reported that metabolic syndrome increases risk of breast cancer and subsequent death from breast cancer among women over 60. Metabolic syndrome is characterized by obesity, high blood sugar levels, impaired glucose tolerance, high blood cholesterol and triglycerides, and high blood pressure. The study was designed to investigate the associations between metabolic syndrome factors (individually and in combination) and breast cancer. Few previous studies have assessed the associations and the results have been inconsistent. The study included 290,000 women from Austria, Norway, and Sweden who were enrolled between 1974 and 2005. Measurements of height, weight, blood pressure, and levels of glucose, cholesterol, and triglycerides were taken at baseline. A total of 4,862 new cases of breast cancer and 633 deaths from breast cancer were identified during the study period.

A 17% lower risk of breast cancer was found among women with metabolic syndrome who were less than 50 years old (in other words, a group that was predominantly premenopausal) compared to those who did not have the syndrome. A lower risk was also found for the individual metabolic syndrome factors among these women, apart from elevated glucose level (which increased risk). The lowest risks were observed among the heaviest women. However, among women at least 60 years of age, a 23% increased risk of breast cancer mortality was found for those with metabolic syndrome. Risk of death was also found to be higher for high blood pressure and high blood sugar levels when considered individually. The strongest association with mortality was observed for increased glucose concentrations. The authors conclude that metabolic syndrome is associated with a reduced risk of breast cancer in women below age 50 with high body mass index, and with an increased risk of breast cancer mortality in women above 60.