Differences in the effects of Asian dust on pulmonary function between adult patients with asthma and those with asthma–chronic obstructive pulmonary disease overlap syndrome

Abstract

Background

Asian dust (AD) exposure exacerbates pulmonary dysfunction in patients with asthma. Asthma–chronic obstructive pulmonary disease overlap syndrome (ACOS), characterized by coexisting symptoms of asthma and chronic obstructive pulmonary disease, is considered a separate disease entity. Previously, we investigated the effects of AD on pulmonary function in adult patients with asthma. Here, we present the findings of our further research on the differences in the effects of AD exposure on pulmonary function between patients with asthma alone and those with ACOS.

Methods

Between March and May 2012, we conducted a panel study wherein we monitored daily peak expiratory flow (PEF) values in 231 adult patients with asthma. These patients were divided into 190 patients with asthma alone and 41 patients with ACOS in this study. Daily AD particle levels were measured using light detection and ranging systems. Two heavy AD days (April 23 and 24) were determined according to the Japan Meteorological Agency definition. A linear mixed model was used to estimate the association between PEF and AD exposure.

Results

Increments in the interquartile range of AD particles (0.018 km⁻¹) led to PEF changes of −0.50 L/min (95% confidence interval, −0.98 to −0.02) in patients with asthma alone and −0.11 L/min (−0.11 to 0.85) in patients with ACOS. The PEF changes after exposure to heavy AD were −2.21 L/min (−4.28 to −0.15) in patients with asthma alone and −2.76 L/min (−6.86 to 1.35) in patients with ACOS. In patients with asthma alone, the highest decrease in PEF values was observed on the heavy AD day, with a subsequent gradual increase over time.

Conclusion

Our results suggest that the effects of AD exposure on pulmonary function differ between patients with asthma alone and ACOS, with the former exhibiting a greater likelihood of decreased pulmonary function after AD exposure.

Keywords:

• Asian dust
• asthma
• asthma–chronic obstructive pulmonary disease overlap syndrome
• peak expiratory flow
• pulmonary function

Acknowledgments

The authors thank Atsushi Shimizu and Nobuo Sugimoto (National Institute for Environmental Studies) for providing LIDAR data. The study was supported by the Environmental Research and Technology Development Fund (5C-1154 and 5-1453) of the Japanese Ministry of the Environment, and Tottori Prefecture. The sponsors had no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the article for publication.

Author contributions

MW, JK, HS, ES, and HK conceived the study. MW, HN, and HS participated in the design. MW, JK, YU, MM, HY, HT, KK, TK, and TT collected the data. MW and HN performed the analysis. MW, HN, JK, and HS drafted the manuscript. All authors had full access to all study data and take full responsibility for the data integrity and accuracy of analysis. All authors further contributed toward data analysis, drafting and critically revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.