Effects of secondhand smoke exposure on asthma morbidity and health care utilization in children: a systematic review and meta-analysis

Background Secondhand smoke (SHS) exposure can trigger asthma exacerbations in children. Different studies have linked increased asthma symptoms, health care use, and deaths in children exposed to SHS, but the risk has not been quantified uniformly across studies. Objective To perform a systematic review and meta-analysis to evaluate and quantify asthma severity and health care use from SHS exposure in children. Methods A systematic review was undertaken to assess the association between asthma severity and SHS in children. Inclusion criteria included studies that evaluated children with SHS exposure and reported outcomes of interest with asthma severity including exacerbations. Random effect models were used to combine the outcomes of interest (hospitalization, emergency department or urgent care visits, severe asthma symptoms, wheeze symptoms, and pulmonary function test results) from the included studies. Results A total of 1,945 studies were identified and 25 studies met the inclusion criteria. Children with asthma and SHS exposure were twice as likely to be hospitalized for asthma (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.20-2.86, P =.01) than children with asthma but without SHS exposure. SHS exposure also was significantly associated with emergency department or urgent care visits (OR 1.66, 95% CI 1.02-2.69, P = 0.04), wheeze symptoms (OR 1.32, 95% CI 1.24, 1.41, P <.001), and lower ratio of forced expiratory volume in 1 second to forced vital capacity (OR -3.34, 95% CI -5.35 to -1.33, P =.001). Conclusion Children with asthma and SHS exposure are nearly twice as likely to be hospitalized with asthma exacerbation and are more likely to have lower pulmonary function test results.