Impact of metabolic syndrome on breast cancer risk varies by age

The presence of metabolic syndrome portends a heightened risk of developing breast cancer among postmenopausal women but appears to be protective among those who are younger, a retrospective study has found.

In a cohort of 13,377,349 women aged >19 years (64,535,186 person-years) from Korean National Health Insurance Service, 3,578,546 (26.8 percent) had metabolic syndrome. A higher number of women with the medical condition were aged >50 years and had body mass index ≥25 kg/m². On the other hand, those without metabolic syndrome were more likely to smoke, drink alcohol, exercise, and have low income.

There were 79,447 and 8,300 women who developed invasive and in situ breast cancer, respectively, regardless of metabolic syndrome. In multivariable Cox proportional hazards models, the risk of all breast cancer types was low in the presence of metabolic syndrome (hazard ratio [HR], 0.954, 95 percent confidence interval [CI], 0.939–0.970).

However, the estimates differed by age such that the breast cancer risk associated with metabolic syndrome was low among women aged ≤50 years (HR, 0.915, 95 percent CI, 0.892–0.939) but high among women aged >50 years, especially those >55 years of age (HR, 1.146, 95 percent CI, 1.123–1.170).

Furthermore, as the number of metabolic syndrome components increased, the risk soared and dropped further in the older age group and ≤50-year age groups, respectively.

The findings highlight a need to assess breast cancer risks in women with metabolic syndrome.