Metabolic syndrome and the risk of breast, endometrial and ovarian cancer among postmenopausal women in the UK Biobank

Background There is some evidence that metabolic syndrome (MetS) is associated with postmenopausal breast and gynaecological cancer. However, results from previous studies have been inconsistent and varied by definition of MetS used. Methods Using data from the UK Biobank, the association between MetS, according to three definitions, and the risk of breast, endometrial and ovarian cancer was assessed among postmenopausal women with serological biomarker data. Cox proportional hazards regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for a range of confounders. Results In total, 4,791 breast, 820 endometrial and 582 ovarian cancers were diagnosed. For all definitions, MetS was associated with a higher risk of breast (harmonized definition; HR 1.11, 95% CI: 1.04-1.19), and endometrial cancer (harmonized definition; HR 2.18, 95% CI: 1.86-2.55) but not ovarian cancer (harmonized definition; HR 1.08, 95% CI: 0.88-1.31). Assessment of the individual MetS components revealed that only abdominal obesity was consistently associated with breast cancer, whilst all components were associated with a higher risk of endometrial cancer. Conclusions In this cohort, MetS and all MetS components were individually associated with a higher risk of endometrial cancer, but only abdominal obesity was consistently associated with an increased risk of breast cancer. No associations were observed between MetS and ovarian cancer risk. Impact These findings underline the need for further mechanistic research to clarify potential causal relationships and to better inform public health strategies to address the rising obesity-related cancer burden, particularly endometrial in postmenopausal women.