Association between high-sensitivity C-reactive protein and metabolic syndrome: systematic review and meta-analysis

Abstract Background Metabolic syndrome (MetS) is a cluster of cardiometabolic abnormalities associated with chronic low-grade systemic inflammation. High-sensitivity C-reactive protein (hs-CRP) is a sensitive biomarker of inflammation and has been proposed as a potential indicator of MetS. However, the magnitude of the association between hs-CRP and MetS remains inconsistent across populations. This systematic review and meta-analysis aimed to quantify the difference in hs-CRP levels between individuals with and without MetS. Methods A systematic search of PubMed/MEDLINE, EMBASE, Scopus, Web of Science, Cochrane Library, Epistemonikos, and gray literature sources was conducted. Eligible observational studies reporting mean and standard deviation of hs-CRP among participants with and without MetS were included. Data were pooled using a random-effects model, and standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated. Subgroup analyses were performed according to geographic region, study design, study setting, fasting status, hs-CRP assay type, and MetS diagnostic criteria. Results Twenty-eight studies involving 71,882 participants (23,945 MetS cases and 47,937 controls) were included. Overall, hs-CRP levels were significantly higher among individuals with MetS than among healthy controls (SMD = 0.95, 95% CI: 0.81–1.10; p < 0.001). Significant heterogeneity was observed across studies (I² = 99.49%, p < 0.001). Subgroup analyses demonstrated higher effect estimates in Europe (SMD = 2.84) and Africa (SMD = 2.63) compared with Asia and the Middle East. The association remained significant across study designs, settings, assay methods, and MetS diagnostic criteria. Conclusions People with metabolic syndrome had greater levels of hs-CRP than people without the condition. However, causal interpretation is constrained by the observational nature of the available data and significant between-study heterogeneity. To ascertain the temporal connection between hs-CRP and metabolic syndrome, prospective longitudinal studies are required.