Associations between exposure to various air pollutants and risk of metabolic syndrome: a systematic review and meta-analysis.

Background: Metabolic Syndrome (MetS) is a widely observed metabolic disorder that is increasingly prevalent worldwide, leading to substantial societal consequences. Previous studies have conducted two separate meta-analyses to investigate the relationship between MetS and air pollutants. However, these studies yielded conflicting results, necessitating a thorough systematic review and meta-analysis to reassess the link between different air pollutants and the risk of developing MetS.

Methods: We conducted a comprehensive search of relevant literature in databases including PubMed, Embase, Cochrane Library, and Web of Science up to October 9, 2023. The search was specifically restricted to publications in the English language. Following the screening of studies investigating the correlation between air pollution and MetS, we utilized random-effects models to calculate pooled effect sizes along with their respective 95% confidence intervals (CIs). We would like to highlight that this study has been registered with PROSPERO, and it can be identified by the registration number CRD42023484421.

Results: The study included twenty-four eligible studies. The results revealed that an increase of 10 μg/m³ in annual concentrations of PM₁, PM_2.5, PM₁₀, NO₂, SO₂, and O₃ was associated with a 29% increase in metabolic syndrome (MetS) risk for PM1 (OR = 1.29 [CI 1.07-1.54]), an 8% increase for PM2.5 (OR = 1.08 [CI 1.06-1.10]), a 17% increase for PM₁₀ (OR = 1.17 [CI 1.08-1.27]), a 24% increase for NO₂ (OR = 1.24 [CI 1.01-1.51]), a 19% increase for SO₂ (OR = 1.19 [CI 1.04-1.36]), and a 10% increase for O₃ (OR = 1.10 [CI 1.07-1.13]).

Conclusion: The findings of this study demonstrate a significant association between exposure to fine particulate matter (PM₁, PM_2.5, PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and the incidence of metabolic syndrome (MetS). Moreover, the results suggest that air pollution exposure could potentially contribute to the development of MetS in humans.