Ambient air pollution and body weight status in adults: A systematic review and meta-analysis

Overweight and obesity have become a global epidemic and concern, and contributed to at least 4.0 million deaths each year worldwide. However, current evidence regarding the impact of air pollution on body weight status remains inconsistent. We therefore conducted a systematic review and meta-analysis to evaluate the effect of long-term exposure to ambient air pollutants on body weight status in adults. Three databases were searched up to Dec 31, 2019 for articles investigating the association of gaseous (sulfur dioxide, nitrogen dioxide, ozone) and particulate (diameter ≤ 10 μm or ≤ 2.5 μm) air pollutants with body weight status. Random effect models were used to estimate the pooled odds ratios (ORs), regression coefficients (β) and their 95% confidence intervals (95% CIs) associated with air pollution. Among twelve studies that were eligible in the systematic review, ten were used to estimate the pooled effect size, and most of them were cross-sectional studies. We identified that ambient air pollution had adverse effects on body weight status. For example, elevated PM_2.5 and O₃ were associated with higher level of body mass index, with the pooled β (95% CIs) of 0.34 (0.30-0.38) and 0.21 (0.17-0.24) per 10 μg/m³ increment, respectively. In addition, increased NO₂, SO₂ and O₃ were associated with higher risk of having overweight/obesity, with the corresponding pooled OR (95% CI) of 1.13 (1.01-1.26), 1.04 (1.01-1.06) and 1.07 (1.02-1.13) per 10 μg/m³ increment. Overall, air pollution is a potential risk factor for body weight status in adults, and more high-quality studies, especially prospective studies from severely polluted regions, are warranted for comprehensive understanding of its health effects.