Objectives Occupational asthma (OA) often interferes with workers’ ability to maintain employment. We synthesized the prevalence of adverse occupational outcome (AOO)—unemployment, chronic sick leave, disability, and early retirement—caused by OA.

Methods Following PRISMA methodological recommendations and PROSPERO registration (CRD42024528750), we searched PubMed, Scopus, and Web of Science for studies published between January 1980 and September 2024 that reported quantitative employment outcomes in adults with OA. Risk of bias was assessed using the Joanna Briggs Institute Checklist for Prevalence Studies. Pooled prevalences were calculated using random-effects generalized linear mixed models on the logit scale with Hartung–Knapp 95% confidence and prediction intervals (CI and PI).

Results A total of 25 studies comprising 3393 participants were included. The pooled prevalence of AOO was 35.9% (95% CI 28.6–43.9; I²=86.0%; 95% PI 10.2–73.4). Prevalence of AOO varied by: (i) data sources (registry/compensation: 50.1% versus clinic: 32.0%; P=0.015); (ii) study size (>80 participants: 43.4% versus ≤80: 27.9%; P=0.033); (iii) baseline forced expiratory volume in 1 second (FEV₁) (≤85% predicted: 38.2% versus >85% predicted: 13.8%; P=0.008); and (iv) exposure duration before symptom onset (>7.1 years: 35.7% versus ≤7.1 years: 15.7%; P=0.015). Heterogeneity across studies was substantial and several subgroups included fewer than five studies.

Conclusions More than one-third of workers with OA experience an AOO. The findings highlight the need for harmonized outcome definitions and for interventions integrating early referral, exposure control, and structured return-to-work programs to avoid AOO.

Key terms adverse occupational outcome; asthma; meta-analysis; occupational asthma; return to work; specific inhalation challenge; systematic review; unemployment

• Supplementary material