Physiological factors linked with metabolic syndrome may play a major role in the risk of postmenopausal breast cancer, according to a study.
The metabolic syndrome, or insulin resistance syndrome, consists of a large number of factors, including abdominal obesity, high blood glucose levels, impaired glucose tolerance, abnormal lipid levels, and high blood pressure.
It is also associated with poor diet and lack of physical activity and can increase the risk for diabetes and heart disease.
The metabolic syndrome is characterised by elevated insulin levels, and scientists have recently proposed that insulin may contribute directly or indirectly to the development of breast cancer.
Researchers suspect that the metabolic syndrome could influence the risk for breast cancer by affecting interrelated hormones, such as insulin, oestrogen, cytokines and growth factors.
"This study suggests that having the metabolic syndrome itself or some of its components may increase a woman's risk of postmenopausal breast cancer. However, much more work is needed to understand the role of these metabolic factors and their interplay with better established breast cancer risk factors, such as reproductive and hormonal factors," said Dr. Geoffrey C. Kabat, senior epidemiologist in the department of epidemiology and population health at Albert Einstein College of Medicine, New York.
In the current study, the researchers have for the first time assessed whether women who met the criteria of having the metabolic syndrome were at greater risk for postmenopausal breast cancer.
For the study, the researchers used existing data from the Women's Health Initiative - a large, national study designed to assess major causes of chronic disease in women.
The participants in the study included postmenopausal women aged 50 to 79 years at enrolment who had repeated measurements of components of metabolic syndrome over an eight-year period.
They were measured for factors including blood levels of glucose, HDL-cholesterol and triglycerides, as well as waist girth and blood pressure.
Kabat said that the results demonstrated a modest positive association of having the metabolic syndrome as a whole.
Of the 4,888 women with baseline measurements who did not have diabetes, 165 incident cases of breast cancer were diagnosed during the follow-up period.
Presence of the metabolic syndrome at baseline was not linked with breast cancer risk.
Kabat, however, said that in analyses that made use of the repeated measurements, "women who had the metabolic syndrome during the three to five years prior to breast cancer diagnosis had roughly a doubling of risk."
The findings also showed significant associations with elevated blood glucose levels, triglycerides and diastolic blood pressure.
The study has been published in Cancer Epidemiology, Biomarkers and Prevention.