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.

Asthma-associated comorbidities in children with and without secondhand smoke exposure.

BACKGROUND: Secondhand smoke (SHS) exposure is known to trigger asthma, but asthma disease severity and comorbidities in children exposed to SHS are not very well quantified. OBJECTIVE: To identify comorbidities and understand health care usage in children with asthma exposed to SHS (cases) compared with children with asthma but without SHS exposure (controls). METHODS: A retrospective nested matched case-and-control study was conducted with children 5 to 18 years old who were enrolled in the Pediatric Asthma Management Program. Pulmonary function testing (spirometry, methacholine challenges, and exhaled nitric oxide) and body mass index were reviewed. Influenza vaccination rates, oral steroid usage, emergency department visits, and hospitalizations were assessed. Network analysis of the 2 groups also was conducted to evaluate for any associations between the variables. RESULTS: Cases had significantly higher body mass index percentiles (>75%, odds ratio [OR] 1.64, 95% confidence interval [CI] 1.22-2.2, P = .001). Cases were less likely to have had a methacholine challenge (OR 0.49, 95% CI 0.36-0.68, P < .001) and an exhaled nitric oxide (OR 0.6, 95% CI 0.37-0.97, P = .04) performed than controls. The ratio of forced expiration volume in 1 second to forced vital capacity and forced expiration volume in 1 second were lower in cases than in controls (P < .05). Cases were less likely to have received an influenza vaccination (OR 0.61, 95% CI 0.45-0.82, P = .001) than controls. Unsupervised multivariable network analysis suggested a lack of discrete and unique subgroups between cases and controls. CONCLUSION: Children with asthma exposed to SHS are more likely to have comorbid conditions such as obesity, more severe asthma, and less health care usage than those not exposed to SHS. Smoking cessation interventions and addressing health disparities could be crucial in this vulnerable population.