Asthma and lower airway disease
Work-exacerbated asthma and occupational asthma: Do they really differ?

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Background

Although work-exacerbated asthma (WEA) is a prevalent condition likely to have an important societal burden, there are limited data on this condition.

Objectives

The aims of this study were (1) to compare the clinical, functional, and inflammatory characteristics of workers with WEA and occupational asthma (OA) and (2) compare health care use and related costs between workers with WEA and OA, as well as between workers with work-related asthma (WRA; ie, WEA plus OA) and those with non–work-related asthma (NWRA) in a prospective study.

Methods

We performed a prospective observational study of workers with and without WRA with a 2-year follow-up. The diagnosis of OA and WEA was based on the positivity and negativity of results on specific inhalation challenges, respectively.

Results

One hundred fifty-four subjects were enrolled: 53 with WEA, 68 with OA, and 33 control asthmatic subjects (NWRA). WEA was associated with more frequent prescriptions of inhaled corticosteroids (odds ratio [OR], 4.4; 95% CI, 1.4-13.6; P = .009), a noneosinophilic phenotype (OR, 0.3; 95% CI, 0.1-0.9; P = .04), a trend toward a lower FEV1 (OR, 0.9; 95% CI, 0.9-1.0; P = .06), and a higher proportion of smokers (OR, 2.5; 95% CI, 0.96-9.7; P = .06) than the diagnosis of OA. The health care use of WRA and related costs were 10-fold higher than those of NWRA.

Conclusion

Workers with WEA appeared to have features of greater asthma severity than workers with OA. In contrast with OA, WEA was associated with a noneosinophilic phenotype. Both OA and WEA were associated with greater health care use and 10-fold higher direct costs than NWRA.

Section snippets

Study design

This was a prospective cohort study of workers with and without WRA with a 2-year follow-up.

Subjects

All asthmatic subjects referred for suspected WRA in 2 tertiary centers of the province of Quebec between 2003 and 2008 were consecutively screened, enrolled, and followed for 2 years. Concomitantly, asthmatic subjects assessed for the first time in the same centers but who were not referred for WRA exacerbations and did not complain of work-related exacerbation of their respiratory symptoms were invited

Clinical characteristics

One hundred eighty-eight subjects were invited to participate in this study, and 34 declined to participate (16 with WRA and 18 with NWRA). One hundred fifty-four subjects were enrolled: 53 with WEA, 68 with OA, and 33 control asthmatic subjects. Their characteristics at baseline are reported in Table I, whereas the characteristics of the subjects with WEA and OA who were at or away from work at baseline are reported in Table II.

Comparison between subjects with WEA and those with OA

After adjusting for age, asthma control, and asthma severity, the

Discussion

This study is the first to report prospectively the clinical, functional, and inflammatory characteristics, as well as health care use and related costs, of subjects with objectively confirmed diagnoses of OA and WEA and subjects with NWRA.

Workers with WEA tended to have more severe asthma than subjects with OA at the time of their initial assessment at the clinic. Although clinical characteristics were not able to differentiate workers with OA from workers with WEA, the eosinophilic phenotype

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    Supported by cooperative agreement no. R01 OH008391 from the Centers for Disease Control and Prevention (CDC).

    Disclosure of potential conflict of interest: C. Lemière has received grants from the CDC and AllerGen; is a consultant for GlaxoSmithKline, Merck, and AstraZeneca; has received payment for lectures, including service on speakers’ bureaus, and payment for development of educational presentations from AstraZeneca. L.-P. Boulet is on the advisory boards for, received research support from, and received lecture fees from AstraZeneca, GlaxoSmithKline, Merck Frosst, and Novartis. H. Villeneuve and K. Maghni have received research support from the CDC. P. Prince has received research support from the CDC and travel expenses from AllerGen NCE. The rest of the authors declare that they have no relevant conflicts of interest.

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