Effect of Air Pollution on Obesity in Children: A Systematic Review and Meta-Analysis

Abstract

Air pollution exposure has been identified as being associated with childhood obesity. Nevertheless, strong evidence of such an association is still lacking. To analyze whether air pollution exposure affects childhood obesity, we conducted a systematic review and meta-analysis utilizing the PRISMA guidelines. Of 7343 studies identified, eight studies that investigated the effects of air pollutant characteristics, including PM_2.5, PM₁₀, PM_coarse, PM_absorbance, NO_x, and NO₂, on childhood obesity were included. The polled effects showed that air pollution is correlated with a substantially increased risk of childhood obesity. PM_2.5 was found to be associated with a significantly increased risk (6%) of childhood obesity (OR 1.06, 95% CI 1.02-1.10, p = 0.003). In addition, PM₁₀, PM_{2.5absorbance}, and NO₂ appeared to significantly increase the risk of obesity in children (OR 1.07, 95% CI 1.04-1.10, p < 0.00; OR 1.23, 95% CI 1.06-1.43, p = 0.07; and OR 1.10, 95% CI 1.04-1.16, p < 0.001, respectively). PM_coarse and NO_x also showed trends towards being associated with an increased risk of childhood obesity (OR 1.07, 95% CI 0.95-1.20, p = 0.291, and OR 1.00, 95% CI 0.99-1.02, p = 0.571, respectively). Strong evidence was found to support the theory that air pollution exposure is one of the factors that increases the risk of childhood obesity.

Keywords: air pollution; children; obesity.

Figure 1

Flow diagram of the studies identified; eight studies were selected to study the effects of air pollutant on childhood obesity [24].

Figure 2

The associations among PM_2.5, PM₁₀, PM_coarse, PM_absorbance, NO₂ and NO_x exposure, and obesity in children were assessed by meta-analysis. A Forest plot of the association between exposure to PM₁₀ and obesity in children was constructed. The size of the black square corresponding to each study is proportional to the sample size, and the center of each square represents the Effect Size (ES). The horizontal line shows the corresponding 95% CI of the ES. The pooled ES is represented by a hollow diamond. CI, confidence interval; I₂ = percentage of the total variability due to between-pollution heterogeneity.

Figure 3

Assessing the publication bias by funnel plot. (a) Funnel plot of the association between PM_2.5 and risk of obesity. (b) Funnel plot of the association between PM₁₀ and risk of obesity. (c) Funnel plot of the association between PM_coarse and risk of obesity. (d) Funnel plot of the association between PM_{2.5absorbrance} and risk of obesity. (e) Funnel plot of the association between NO₂ and risk of obesity. (f) Funnel plot of the association between NO_x and risk of obesity.