Associations between occupational inhalation risks and FeNO levels in airway obstruction patients: results from the National Health and Nutrition Examination Survey, 2007–2012

Abstract

Purpose

To investigate associations between occupational inhalation risks and fractional exhaled nitric oxide (FeNO) levels in patients with chronic obstructive pulmonary disease (COPD).

Patients and methods

Data of 16,486 subjects who had undergone spirometry with pre-bronchodilator and post-bronchodilator lung function assessment were retrieved from the National Health and Nutrition Examination Survey, 2007–2012 database. After excluding 2,638 subjects with missing spirometry values, data of 13,336 subjects were included for analysis. Factors associated with occupational inhalation, FeNO levels and COPD were analyzed using logistic regression analysis.

Results

COPD was associated with occupational exposures to mineral dusts, organic dusts, exhaust fumes, other fumes, and second-hand smoking (P<0.05). Long-term exposure to these occupational hazards carried significantly higher risk for subjects with COPD than for controls (crude odds ratios [ORs]: mineral dusts: 2.364, organic dusts: 2.427, exhaust fumes: 2.728, other fumes: 2.144). In subgroup analysis, COPD correlated positively with long-term exposures to organic dusts and exhaust fumes in subjects with FeNO ≤50 ppb (ORs 1.361 and 1.314, respectively); conversely, COPD correlated negatively with intermediate to long-term exposures to organic dusts and exhaust fumes in those with FeNO >50 ppb (ORs 0.058 and 0.210, respectively).

Conclusion

Occupational exposures to airborne pollutants carries higher risk of COPD than non-exposure and the risk is higher the longer the duration of exposure. Exposure–response relationships are inconsistent in subjects with suspected asthmatic airway inflammation (FeNO ≥50 ppb). More careful risk assessment is needed in occupational inhalation exposure, since COPD with asthmatic airway inflammation, or asthma-COPD overlapping syndrome, may have the distinguishing features of both COPD and asthma.

Keywords:

• chronic obstructive pulmonary disease
• COPD
• fractional exhaled nitric oxide
• FeNO
• occupational inhalation risk

Acknowledgments

The authors wish to thank the NCHS for creating and releasing the NHANES data to clinical researchers. We acknowledge that the interpretation and reporting of these data are the sole responsibility of the authors.

This study was supported by a grant from the Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation (TCRD-TPE-106-RT-1).

Author contributions

Yi-Chih Huang: conception and design; acquisition of data; drafting of the manuscript; final approval of the manuscript; statistical analysis; literature research; obtaining funding.

Mei-Chen Yang: conception and design; analysis and interpretation of data; critical revision of the manuscript; final approval of the manuscript; guarantor of integrity of the entire study; definition of intellectual content; administrative, technical or material support; supervision.

Disclosure

The authors report no conflicts of interest in this work.