The effect of metabolic syndrome on bone mineral density in men and women: a systematic review & meta-analysis

Metabolic syndrome (MetS) is associated with alterations in body composition and metabolic health, however its impact on bone mineral density (BMD) remains unclear, with potential sex- and site-specific differences. We systematically searched PubMed, Scopus, MEDLINE and Google Scholar for cross-sectional studies published within the last 10 years to investigate the impact of MetS on BMD. Lumbar spine (LS), femoral neck (FN) and total hip (TH) BMD were utilised as outcomes of interest. The included studies encompassed populations from East Asia, Southeast Asia, the Middle East, Europe and Latin America. Meta-analysis utilising a random-effects model, compared BMD between participants with and without MetS, subgroup analyses by sex and menopausal status and timeframe-stratified sensitivity analysis. Twelve studies reached the synthesis stage, with overall quality found to be low to moderate risk of bias. Men with MetS had significantly higher BMD at the LS ( p = 0.03) and FN ( p = 0.003), with a significant pooled effect across skeletal sites ( Z = 5.57, p < 0.00001). In women, no significant association between MetS and overall BMD was observed. However, subgroup analyses demonstrated that postmenopausal women without MetS had significantly higher FN and LS BMD compared with those with MetS (FN: Z = 2.14, p = 0.03; LS: Z = 2.02, p = 0.04). Sensitivity analysis demonstrated a larger pooled effect for LS BMD in woman in studies with assessment periods of one year or less. MetS is tentatively associated with sex- and site-specific differences in BMD based on observational studies, with potential effect-size differentials according to assessment chronology. Further research is warranted to clarify these associations and their potential clinical implications using higher-quality trial data.