Indoor Dampness and Air Irritation Linked to ICS Starts

Key Takeaways

• In this Swedish adult cohort, floor dampness, irritating air at home, and prior occupational gas, smoke, or dust exposure were each associated with significantly higher later inhaled corticosteroid (ICS) initiation.
• Irritating air at home was also associated with self-reported asthma medication use at baseline.
• Traffic exposure at home was associated with baseline self-reported asthma medication use but not with later ICS initiation.
• Time-to-event analyses suggested that the occupational exposure signal emerged later than the curves for floor dampness and irritating air at home.

Respiratory complaints tied to damp indoor spaces or irritating workplace air can precede a clearer controller-treatment trajectory in adults. The population-based REGAL study drew on the Respiratory Health in Northern Europe (RHINE III) and Global Allergy and Asthma European Network (GA2LEN) cohorts, using questionnaires completed in 2008–2010 and prescription-registry linkage spanning 2005–2018. The analysis included 31,768 adults from Stockholm, Gothenburg, Uppsala, and Umeå and captured self-reported water damage, floor dampness, visible mold, irritating air at home, troublesome traffic near home, cleaning-related work, and previous occupational gas, smoke, or dust exposure. ICS initiation was defined as at least 2 filled ICS-containing inhaler prescriptions within 12 months, with the second fill marking the start date. Adjusted models included sex, age, body mass index (BMI), smoking history, and educational level, with sensitivity analyses in never-smokers and in never-smokers younger than 50 years.

During follow-up, 5.3% of participants initiated ICS over a median 10.7 years. The strongest home-exposure associations for future ICS initiation were irritating air at home, HR 1.46 (95% CI 1.29–1.65), and floor dampness at home, HR 1.42 (95% CI 1.14–1.77).

Previous occupational exposure to gas, smoke, or dust was also associated with future ICS initiation, HR 1.25 (95% CI 1.12–1.40). Traffic exposure at home was associated with baseline self-reported asthma medication use, OR 1.48 (95% CI 1.21–1.81), but not with later ICS initiation. This overall pattern persisted in never-smokers. In never-smokers younger than 50 years, the floor dampness signal did not persist. Among participants with asthma-related symptoms at baseline, floor dampness remained associated with later ICS initiation. Kaplan-Meier curves separated earlier for floor dampness and irritating air than for occupational exposure, indicating a later-emerging workplace signal.

Because the exposures were self-reported, the baseline medication analysis was cross-sectional, and clinical measurements to confirm asthma diagnosis were not available, the findings remained associative. The authors described registry-defined ICS initiation as an objective prescription-based proxy for asthma-related morbidity rather than direct confirmation of asthma onset or severity, and they noted that multiple testing could have introduced some Type I error. The cohort was drawn from four Swedish cities, so these findings reflect that setting rather than implying direct U.S. applicability.

The authors concluded that indoor dampness, perceived irritating air at home, and occupational gas, smoke, or dust exposure were associated with baseline asthma medication use and later ICS initiation in this Swedish adult cohort. In the same analysis, traffic exposure appeared limited to the baseline medication outcome rather than later controller starts.

Clinician Questions

Why did the REGAL analysis require two ICS prescriptions within 12 months to define treatment initiation?

The investigators counted ICS initiation only after 2 filled ICS-containing inhaler prescriptions within 12 months and used the second fill as the start date because a single prescription could reflect short-term treatment for an acute airway infection rather than ongoing controller therapy.

Did the home and occupational exposure associations hold up in never-smokers?

In sensitivity analyses restricted to never-smokers, the main pattern of associations between home or occupational exposures and later ICS initiation remained. When the analysis was narrowed further to never-smokers younger than 50 years, the floor dampness association with later ICS initiation was no longer significant, while the overall pattern otherwise remained similar.

What did the timing analysis suggest about occupational gas, smoke, or dust exposure and later ICS use?

Kaplan–Meier analyses showed higher unadjusted ICS initiation among participants with previous occupational gas, smoke, or dust exposure, but the separation from non-exposed participants emerged later in follow-up, becoming apparent after about seven years.