Maternal and Indoor Smoking Are Associated with Increased Risk of Acute Respiratory Infection in Under-Five Children: A Meta-Analysis of National Survey Data from Eight Asia-Pacific Countries.

Background: Early exposure to tobacco smoke can harm children's developing respiratory systems, increasing the risk of acute and long-term health consequences. This study examined the association of maternal and indoor smoking with acute respiratory infection (ARI) in under-five children living in eight Asia-Pacific countries. Methods: We analysed Demographic and Health Survey data collected between 2015 and 2022. A logistic regression model was fitted separately to each country's data to obtain the odds of ARI in children for maternal tobacco use, daily indoor smoking, and occasional indoor smoking. Then, a meta-analysis using the Der Simonian and Laird method was used to obtain a pooled odds ratio (pOR) of ARI across the included countries. Results: We included a weighted sample of 302,841 children, among whom the prevalence of ARI was 4.12% (95% CI: 4.05, 4.19). The pooled prevalence of maternal tobacco use and daily indoor smoking was 3.45% (95% CI: 3.38, 3.51) and 29.61% (95% CI: 29.45, 29.77), respectively. In random-effects meta-analyses, exposure to daily indoor smoking (pOR = 1.13; 95% CI: 1.02, 1.25) and occasional indoor smoking (pOR = 1.23; 95% CI: 1.13, 1.35) were both associated with increased odds of ARI, as was maternal tobacco use (pOR = 1.67; 95% CI: 1.21, 2.31). Conclusions: Secondhand smoke exposure was associated with higher odds of ARI among under-five children, underscoring the need for smoke-free home policies across Asia-Pacific countries, particularly as the tobacco industry expands marketing and lobbying against such policies in low-income settings.