Prevalence of asthma among never smokers in the US population

Background:

Approximately 25 million people (8.2% of the US population) have asthma, and this rate is climbing. We examined self-reported never-smoking participants with asthma and assessed the association of second-hand smoke (SHS) exposure with asthma.

Methods:

Data were obtained from the 1999-2012 NHANES, a nationally representative sample of the US population. The sample was never-smoking participants 20+ years currently living with asthma (n=1,915). Participants were asked "still have asthma?", "had asthma attack in past year?", and "visited emergency room (ER) for asthma in past year?" We compared participants by sociodemographics, SHS exposure, cadmium levels, and FEV1/FVC ratios using Chi-squared tests and regression models. All analyses were adjusted for sample weights to account for complex survey design.

Results:

The prevalence of never-smoking participants who "still have asthma" was 51.0%. Females and older individuals were more likely than their male and younger counterparts to "still have asthma" (p<0.0001 each). Compared to non-asthmatics, those who "still have asthma" had higher cadmium levels (p=0.0112) and lower FEV1/FVC ratios (p=0.0084). Females were more likely than males to have an "asthma attack in the past year" (p=0.0293) and "visit an ER in the past year" (p=0.0019). SHS exposure was lower in asthmatics who had an "asthma attack in the past year" (p=0.0137) but higher for those with an "ER visit in the past year" (p=0.0048) compared with non-asthmatics. Compared to those without asthma, the ethnicity of asthmatics (Mexican American, non-Hispanic White, non-Hispanic Black, Other Hispanic, Other) played a role in "visits to the ER in the past year" (p=0.05).

Conclusion:

For the never smoking population with asthma, variations were seen by sociodemographic, SHS exposure, and biomarkers. Understanding these disparities can help to inform healthcare prevention policies.