Small airway dysfunction was linked to more asthma exacerbations

Design

Single-centre observational cohort, about 12 months' follow-up

Population

167 adults with stable asthma, Taiwan

Primary outcome

Time to acute exacerbation

Effect

Adjusted HR 3.26 (95% CI 1.47-7.23) for small airway dysfunction

This cohort followed 167 adults with stable asthma in Taiwan, each with spirometry and impulse oscillometry at baseline and about a year later. Small airway dysfunction was defined by oscillometry as a difference between resistance at 5 Hz and 20 Hz above 0.07 kPa/(L/s).

It was present in 134 of 167 (80%). Those with it had exacerbations more often during follow-up (43% vs 21%). After adjustment, small airway dysfunction (HR 3.26, 95% CI 1.47 to 7.23) and a previous exacerbation (HR 2.61, 1.40 to 4.85) were each independently associated with a future attack.

This is a small, single-centre observational study, and oscillometry is not widely available on medical wards. But it supports a familiar clinical point: normal-looking spirometry does not mean the airways are quiet.

• Ask about exacerbations in the past year at every asthma review; a previous attack was a strong predictor.
• Consider oscillometry, where available, for patients with poor control despite near-normal spirometry.
• Check inhaler technique and adherence before stepping up treatment.
• Treat a patient with recent exacerbations as high risk even if their spirometry looks reassuring.

Why it matters

It suggests the standard spirometry-based review can miss the patients most likely to be readmitted.

Don't overread it

This is an association in 167 patients; it does not show that treating the small airways prevents exacerbations.

The statistics, in plain English

A hazard ratio of 3.26 means exacerbations occurred at about three times the rate in patients with small airway dysfunction. The wide interval (1.47 to 7.23) reflects the small study, so the true size is uncertain.

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