Cigarette smoking and PM might jointly exacerbate the risk of metabolic syndrome.

BACKGROUND

Cigarette smoking and particulate matter (PM) with aerodynamic diameter < 2.5 μm (PM) are major preventable cardiovascular mortality and morbidity promoters. Their joint role in metabolic syndrome (MS) pathogenesis is unknown. We determined the risk of MS based on PM and cigarette smoking in Taiwanese adults.

METHODS

The study included 126,366 Taiwanese between 30 and 70 years old with no personal history of cancer. The Taiwan Biobank (TWB) contained information on MS, cigarette smoking, and covariates, while the Environmental Protection Administration (EPA), Taiwan, contained the PM information. Individuals were categorized as current, former, and nonsmokers. PM levels were categorized into quartiles: PM ≤ Q1, Q1 < PM ≤ Q2, Q2 < PM ≤ Q3, and PM > Q3, corresponding to PM ≤ 27.137, 27.137 < PM ≤ 32.589, 32.589 < PM ≤ 38.205, and PM > 38.205 μg/m.

RESULTS

The prevalence of MS was significantly different according to PM exposure (-value = 0.0280) and cigarette smoking (-value < 0.0001). Higher PM levels were significantly associated with a higher risk of MS: odds ratio (OR); 95% confidence interval (CI) = 1.058; 1.014-1.104, 1.185; 1.134-1.238, and 1.149; 1.101-1.200 for 27.137 < PM ≤ 32.589, 32.589 < PM ≤ 38.205, and PM > 38.205 μg/m, respectively. The risk of MS was significantly higher among former and current smokers with OR; 95% CI = 1.062; 1.008-1.118 and 1.531; 1.450-1.616, respectively, and a dose-dependent -value < 0.0001. The interaction between both exposures regarding MS was significant (-value = 0.0157). Stratification by cigarette smoking revealed a significant risk of MS due to PM exposure among nonsmokers: OR (95% CI) = 1.074 (1.022-1.128), 1.226 (1.166-1.290), and 1.187 (1.129-1.247) for 27.137 < PM ≤ 32.589, 32.589 < PM ≤ 38.205, and PM > 38.205 μg/m, respectively. According to PM quartiles, current smokers had a higher risk of MS, regardless of PM levels (OR); 95% CI = 1.605; 1.444-1.785, 1.561; 1.409-1.728, 1.359; 1.211-1.524, and 1.585; 1.418-1.772 for PM ≤ 27.137, 27.137 < PM ≤ 32.589, 32.589 < PM ≤ 38.205, and PM > 38.205 μg/m, respectively. After combining both exposures, the group, current smokers; PM > 38.205 μg/m had the highest odds (1.801; 95% CI =1.625-1.995).

CONCLUSION

PM and cigarette smoking were independently and jointly associated with a higher risk of MS. Stratified analyses revealed that cigarette smoking might have a much higher effect on MS than PM. Nonetheless, exposure to both PM and cigarette smoking could compound the risk of MS.