Short-Term Secondhand Smoke Exposure Effects in Asthma vs COPD

In individuals with asthma and chronic obstructive pulmonary disease (COPD), acute, short-term secondhand smoke (SHS) exposure has been shown to modify spirometric indices and is a known hazard. However, the results of an intervention trial (ClinicalTrials.gov Identifier: NCT03074734) suggest that this effect may only be significant in asthma and not COPD. Results of the analysis were published in the Journal of Asthma.

Investigators sought to evaluate the acute respiratory effect on lung function that is associated with short-term SHS exposure in patients with COPD and asthma. The clinical trial was led by Tobacco Free Research Institute Ireland, and conducted in Liberia (Czechia), Dublin (Ireland), and Madrid (Spain). Measurements were obtained both before and after exposure to SHS in legal outdoor smoking areas. Exhaled carbon monoxide (CO), forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and peak expiratory flow rate (PEFR) were calculated in all patients, both before SHS exposure and 24 hours after SHS exposure.

The study enrolled a total of 60 patients; 30 of whom had COPD and 30 of whom had asthma. Overall, 58.3% (35 of 60) of the participants were women. Inclusion criteria for the patients with asthma were confirmed physician-diagnosed asthma, being aged ≥18 years, being fully ambulatory, and having a history of frequently visiting outdoor smoking areas. Inclusion criteria for the participants with COPD were physician-diagnosed COPD with confirmed airflow limitation on postbronchial spirometry with FEV₁/FVC <0.7, being aged 50 to 70 years, being a current or a former smoker, being fully ambulatory, and having a history of frequent visits to outdoor smoking areas.

No significant differences were reported in exhaled CO between before and 24-hours after exposure in men (P =.169) or in women (P =.210). A statistically significant reduction was observed, however, in FVC in the participants with asthma (P =.02). Further, significant decreases were also seen in FEV₁ (P =.02), FVC (P =.04), and PEFR (P =.04) in women with asthma, but not in men.

In contrast, none of the observed reductions in respiratory measurements in participants with COPD were statistically significant. At 24 hours following SHS exposure, no increases in symptoms, respiratory medication use, or healthcare services were reported.

The investigators concluded that although short-term SHS exposure had a significant effect on pulmonary function in women with asthma, spirometric values were not significantly modified in the participants with COPD 24 hours after exposure. They added that new research should explore the long-term effects of SHS exposure in these individuals via continuous monitoring of lung function (with home, portable spirometers) and respiratory symptoms.

Reference

Keogan S, Alonso T, Sunday S, et al; for the TackSHS Project Investigators. Lung function changes in patients with chronic obstructive pulmonary disease (COPD) and asthma exposed to secondhand smoke in outdoor areas [published online May 22, 2020]. J Asthma. doi:10.1080/02770903.2020.1766062