Air pollution, greenspace, and metabolic syndrome in older Czech and Swiss populations

The prevalence of metabolic syndrome (MetS) has increased rapidly, with considerable variation between European countries. The study examined the relationship between air pollutants, greenspace, and MetS and its components in the Czech and Swiss populations.

Cross-sectional data from the Czech Health, Alcohol and Psychosocial Factors in Eastern Europe (HAPIEE) (n = 4,931) and the Swiss cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) (n = 4,422) cohorts included participants aged 44-73 years. MetS was defined as abdominal obesity plus two additional components (hypertension, diabetes, low high-density lipoprotein cholesterol, and elevated triglycerides). Annual mean concentrations of PM₁₀, PM_2.5, NO₂, and greenspace (defined as the annual mean of normalized difference vegetation index within 500 m) were assigned to the individual residential level. We estimated odds ratios (OR) using multivariable logistic regressions with cluster-robust standard error, controlling for multiple confounders.

The prevalence of MetS was significantly higher in the Czech (51.1%) compared with Swiss (35.8%) population as were the concentration means of PM₁₀ and PM_2.5. In HAPIEE, a 5 μg/m³ increase in PM_2.5 was associated with 14% higher odds of MetS (OR = 1.14; 95% confidence interval [CI] = 1.01, 1.28). In SAPALDIA, no evidence was found for the associations between air pollutants and MetS (e.g. OR = 1.01; 95% CI = 0.90, 1.13 for PM_2.5). No protective effects of normalized difference vegetation index on MetS were observed. Upon inspection of MetS components, PM_2.5 and PM₁₀ exposures were associated with higher odds of hypertension and elevated triglycerides in HAPIEE only, while PM_2.5, PM_10, and NO₂ were associated with higher odds of diabetes in SAPALDIA only.

Individuals with higher exposures to PM_2.5 may be at higher risk of MetS. The differential associations with MetS components between the cohorts deserve further investigation.