Smoking was associated with poorer asthma control in cross-sectional analyses, but longitudinal analyses showed that cigarettes and e-cigarettes were not associated with new-onset asthma or worsening of asthma over time, according to study findings published in BMJ Open Respiratory Research.

In the Population Assessment of Tobacco and Health (PATH) study, researchers evaluated relationships between tobacco use and asthma diagnosis and symptoms among individuals aged 18 to 39 years without comorbid chronic obstructive pulmonary disease (COPD).

The analysis used data from wave 1 (2013-2014) of PATH, which oversampled adults who used tobacco, young adults (aged 18-24 years), and Black adults. Respiratory symptoms were initially assessed in wave 2 (2014-2015), which was the baseline assessment. Follow-up data were obtained from wave 3 (2015-2016) and wave 4 (2016-2017).

Participants reported use of combustible products such as cigarettes, traditional cigars, cigarillos, filtered cigars, pipe tobacco, and hookah, as well as noncombustible products such as e-cigarettes and chewing tobacco in their lifetime and for the previous month.

The study authors assessed the associations between tobacco use and covariates and then examined cross-sectional associations between tobacco use at wave 2 and lifetime asthma diagnosis and asthma control at wave 2. The researchers then evaluated longitudinal associations between tobacco use in wave 2 and new asthma diagnoses at waves 3 and 4 and Asthma Control Test (ACT) scores at wave 3.

Although cigarette use was associated with worse asthma control, there were no longitudinal associations between combustible tobacco or e-cigarette use and new onset or worsening asthma in these preliminary analyses.

A total of 10,267 participants (50.4% female; 58.3% White) were included. Of those, 8835 reported never having asthma, and 1432 reported having asthma. The weighted prevalence of lifetime asthma was 12.2% (SE=0.4).

Among patients with asthma, 288 had used asthma medication within the previous 12 months. Tobacco use was similar among those who never had asthma, those with untreated asthma, and those with treated asthma. However, participants with untreated asthma were more likely to be individuals who had smoked cigars in the past 30 days and those who currently smoked marijuana vs individuals from other study groups (P =.03 and P <.01, respectively).

According to multivariable models, significant associations were found between lifetime asthma (model 2) and marijuana use (15.1% vs 11.7%; aRR 1.26; 95% CI, 1.07-1.48); current cigar use (lifetime prevalence 14.5% in past 30-day cigar smoking group vs 11.9% in non-cigar smoking in past 30 days group, adjusted risk ratios [aRR] 1.17; 95% CI, 1.00-1.36); and weight status (16.4% vs 11.0%; aRR 1.62; 95% CI, 1.30-2.01 for participants with class 2 obesity vs normal weight).

New-onset asthma at waves 3 and 4 was diagnosed in 1.3% (SE=0.2) of young adults aged 18 to 24 years, and 0.9% (SE=0.1) of those aged 25 to 39 years. No association between any type of tobacco use and new-onset asthma was observed in the multivariable longitudinal analyses (models 1 and 2).

Participants’ mean ACT score was about 1 point lower for combustible tobacco users vs individuals who had never used tobacco (22.4 [SE=0.1] vs 23.6 [SE=0.2], respectively, 2-sample t-test P <.01).

According to the cross-sectional, adjusted, multivariable analyses of asthma control, ACT scores were lower in current combustible tobacco users (beta = -0.86; 95% CI, -1.32 to -0.39; model 1) and cigarette users (beta = -1.14; 95% CI, -1.66 to -0.62; model 2). Significant associations also were found between asthma control and sex (male sex beta=0.47; 95% CI, 0.16-0.78) and having some college education (beta=0.72; 95% CI, 0.13-1.32). ACT scores for patients who received treatment for asthma were lower than those in participants with untreated asthma (beta = -3.26; 95% CI, -4.05 to -2.46; model 1).

Longitudinal multivariable analyses revealed little association with mean ACT score over time (wave 3 ACT score, controlling for wave 2 ACT score), and no tobacco use category in wave 2 was associated with ACT score in wave 3.

Among several limitations, the PATH study did not include information on asthma subtypes, and data for tobacco, asthma, and asthma symptoms only were available for waves 2 through 4. Also, PATH did not assess allergy or atopy, environmental ozone, environmental air pollution, and prenatal smoke exposure.

“Although cigarette use was associated with worse asthma control, there were no longitudinal associations between combustible tobacco or e-cigarette use and new onset or worsening asthma in these preliminary analyses,” the study authors concluded. “Future research on tobacco and adult asthma should select samples to avoid confounding comorbid conditions and carefully adjust for other smoke exposures,” the researchers added.

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