Conclusions
The epidemiological evidence summarized in our metaanalysis supports the hypothesis that MS is associated with a moderately increased risk for PBC. All components of the syndrome, except triglycerides, show some association with the increased risk, although no single component explains the full risk associated with the syndrome; moreover, the risk conveyed by MS is greater than the sum of its parts. Future epidemiological studies should adopt the same definition of MS and aim for a more comprehensive consideration of covariates to allow for a far more comprehensive control of confounding. The increasing incidence of MS and breast cancer worldwide necessitates public health strategies based on lifestyle changes, which have been demonstrated to help fight MS. In the European Prospective Investigation into Cancer and Nutrition study, adherence to Mediterranean diet was associated with a reduced risk of breast cancer in postmenopausal, but not premenopausal, women.