Among adults who have both asthma and type 2 diabetes, starting tirzepatide rather than semaglutide made no difference to the chance of an asthma attack over a year. A US multicentre analysis of 16,352 matched patients, published on 7 September 2026, found that 11.0% of the tirzepatide group and 11.1% of the semaglutide group had an exacerbation — a hazard ratio of exactly 1.00. The only difference between the drugs was small and secondary: tirzepatide patients were slightly less likely to need a rescue inhaler.
What the study measured
The researchers, at the University of Michigan and Taipei Medical University, used the TriNetX US Collaborative Network, a federated database of electronic health records. They identified adults with both asthma and type 2 diabetes who started either one of these drugs between 1 June 2022 and 31 December 2024 and followed them for twelve months; the study period closed on 1 December 2025. Propensity score matching balanced the two groups one-to-one on recorded baseline characteristics, leaving 8,176 patients in each arm.
The primary outcome was time to a first asthma exacerbation. It came out at 11.0% on tirzepatide against 11.1% on semaglutide: a hazard ratio of 1.00, with a 95% confidence interval running from 0.91 to 1.10. That interval is worth reading properly. It is narrow and centred on 1.00, which makes this an informative null rather than an inconclusive one — it largely rules out a difference bigger than about 10% in either direction, instead of simply failing to find one. The finding held across the sensitivity and subgroup analyses the authors ran.
Of the two secondary outcomes, systemic corticosteroid use was also a null: hazard ratio 1.01, interval 0.96 to 1.05. Short-acting beta-agonist use — the rescue inhaler — was modestly lower on tirzepatide, at 0.92 with an interval of 0.88 to 0.96. An 8% relative reduction whose interval clears 1.00 is statistically real, but it is a small effect on the least serious of the three measures.
The framing matters as much as the result. GLP-1 drugs have been widely floated as helping asthma, on the reasoning that excess weight worsens asthma control and these drugs treat it. This study does not test that idea at all. Both arms took an incretin-based drug, so there is no untreated comparison group: the question asked is narrower, whether the dual GIP/GLP-1 agonist does better than the GLP-1 agonist alone. For attacks, the answer is no.
For someone weighing up the two drugs, that is a small piece of reassurance rather than a reason to switch. If you have asthma alongside type 2 diabetes, this says asthma should not be the deciding factor between them, and the inhaler difference is too small to make it one. It also says nothing about people taking these drugs for weight alone without diabetes, who were not in this cohort.
What it cannot show
This is a retrospective analysis of medical records, not a randomised trial, and the authors say a trial is still needed to settle the wider question. Propensity matching balances the characteristics that were recorded; it cannot balance the ones that were not, and the reasons a clinician reaches for tirzepatide over semaglutide for a particular patient — insurance coverage, previous response, how much weight loss is being sought — are largely invisible in data of this kind.
Two further limits are worth stating. Exacerbations and inhaler use were identified from coded records, which capture prescriptions and clinical encounters rather than what patients actually experienced, and twelve months is a short window for a condition that varies with the season and the year. The journal, the Journal of Asthma and Allergy, is an open-access title outside the front rank of respiratory journals, so the result deserves confirmation elsewhere. The authors declare no conflicts of interest.
Sources: Hung CT, An CY, Suk CW, Lee TW, Hung SH. “Association of Tirzepatide versus Semaglutide with Risk of Asthma Exacerbation in Patients with Asthma and Type 2 Diabetes: A US Multicenter Retrospective Cohort Study.” Journal of Asthma and Allergy, 7 September 2026;19:637738, doi:10.2147/JAA.S637738 · PubMed record, PMID 42730051 · free full text at PubMed Central (PMC13565390).
