Clinical Importance of Work-Exacerbated Asthma: Findings From a Prospective Asthma Cohort in a Highly Industrialized City in Korea

Abstract

Purpose: Work-related asthma (WRA) occupies about 10%-30% of all asthma cases. Among 2 subtypes of WRA (occupational asthma [OA] and work-exacerbated asthma [WEA]), the rate of WEA has been reported to increase recently. WRA is described as having worse characteristics than non-WRA (NWRA), while WEA is known to show similar severity to OA in terms of symptoms and exacerbations. However, these data were mainly based on indirect surveys. Ulsan is a highly industrialized city in Korea; therefore, it is estimated to have a high incidence of WRA. This study aimed to identify the characteristics of WRA in the city.

Methods: This was a prospective asthma cohort study of individuals diagnosed with asthma and treated at Ulsan University Hospital between Jan 2015 and Dec 2016. Baseline characteristics and work-related inquiry (9 questionnaires) were investigated at enrollment. Various severity indices and job change were then investigated for the longitudinal analysis at 12 months after enrollment.

Results: In total, 217 asthma patients completed the study. WRA accounted for 17% (36/217), with an equal number of WEA and OA (18 patients each). Before the work-related survey, only 33% (n = 12) of WRA patients (22% [4/18] of WEA and 44% [8/18] of OA) were diagnosed with WRA by the attending physicians. Compared to the NWRA group and the OA subgroup, the WEA subgroup had more outpatient visits, more oral corticosteroids prescriptions, and trends of low asthma control test scores and severe asthma. The rate of job change was markedly lower in the WEA subgroup than in the OA subgroup (20% vs. 5%).

Conclusions: The overall prevalence of WRA (17%) was similar to those of previous studies, but the share of WEA was high (50% of WRA). WEA was more severe than OA or NWRA. The possible reason for this severity is ongoing workplace exposure.

Keywords: Asthma; asthma, occupational; work.

Fig. 1. Decision logic for WRA (OA and WEA) and NWRA. Using the work-relatedness inquiry, the time of asthma occurrence and work-exacerbation were investigated. NWRA was defined as a case of asthma without work-exacerbation. WEA was defined as a case of asthma when there was work-exacerbation, but the beginning of asthma symptoms was before the start of a job. OA was defined as a case of asthma when there was work-exacerbation, and the beginning of asthma symptoms was after the start of a job. IIOA (RADS) was defined as OA of acute asthma symptom onset (within days) after a high-level exposure of an irritant.

NWRA, non-work-related asthma; WRA, work-related asthma; WEA, work-exacerbated asthma; OA, occupational asthma; SIOA, sensitizer-induced occupational asthma; IIOA, irritant-induced occupational asthma; RADS, reactive airways dysfunction syndrome.

Fig. 2. Prevalence of WRA (OA and WEA) and NWRA. Of the 217 asthma patients, 36 (17%) had WRA and 181 (83%) had NWRA. OA (n = 18) and WEA (n = 18) accounted for an equal proportion of WRA.

NWRA, non-work-related asthma; WRA, work-related asthma; WEA, work-exacerbated asthma; OA, occupational asthma; SIOA, sensitizer-induced occupational asthma; IIOA, irritant-induced occupational asthma; RADS, reactive airways dysfunction syndrome.