Tirzepatide, a dual GIP and GLP-1 receptor agonist, reduced the apnea-hypopnea index by roughly 25 to 30 events per hour and produced weight loss of 18% to 20% over 52 weeks in adults with moderate-to-severe obstructive sleep apnea and obesity, according to two phase 3 trials published in The New England Journal of Medicine. The findings, from the SURMOUNT-OSA program of 469 participants, provided the pivotal evidence for the FDA’s December 2024 approval of tirzepatide (Zepbound) as the first medicine specifically indicated for obstructive sleep apnea (OSA).
Why OSA has needed a drug
Obstructive sleep apnea affects an estimated 900 million adults worldwide, with about 40% of cases moderate-to-severe. Untreated OSA raises the risk of hypertension, cardiovascular disease, stroke, and metabolic complications. The mainstay treatment for four decades has been continuous positive airway pressure (CPAP), which is highly effective when used. Real-world adherence, however, is a persistent problem, with roughly half of prescribed patients discontinuing CPAP within a year. Existing drug treatments only address daytime sleepiness. Until the SURMOUNT-OSA results, no medicine had been approved for the underlying airway obstruction itself.
How tirzepatide works
Tirzepatide is a once-weekly subcutaneous injection that activates two gut hormone receptors, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Both signals reduce appetite, slow gastric emptying, and improve glucose handling, and together they produce weight loss substantially larger than that seen with GLP-1 monotherapy. In OSA, the benefit is indirect. Excess weight, particularly fat around the neck and upper airway, narrows the airway during sleep. Reducing that weight reduces the airway collapse that drives sleep apnea, which is why tirzepatide can improve OSA without acting on the airway directly.
How the trials were designed
SURMOUNT-OSA comprised two independent, 52-week, multicenter, randomized, double-blind, placebo-controlled phase 3 trials conducted under a master protocol at sites in nine countries. Trial 1 enrolled 234 participants who were unable or unwilling to use CPAP; Trial 2 enrolled 235 participants already using CPAP and planning to continue during the trial. All participants had a body mass index of at least 30 kg/m² and an apnea-hypopnea index (AHI) of 15 events per hour or greater, defining moderate-to-severe OSA. Participants were randomized 1:1 to weekly tirzepatide, titrated to a maximum tolerated dose of 10 or 15 mg, or to placebo. Both arms received lifestyle intervention including a calorie-deficit diet and physical activity.
The primary endpoint was change from baseline in AHI at week 52. Key secondary endpoints included percent change in AHI, body weight, hypoxic burden, high-sensitivity C-reactive protein, systolic blood pressure, and patient-reported sleep outcomes.
What the trials found
In Trial 1 (no CPAP), tirzepatide reduced AHI by 25.3 events per hour compared with 5.3 events per hour on placebo, a treatment difference of 20.0 events per hour (95% CI, −25.8 to −14.2; P<0.001). In Trial 2 (on CPAP), tirzepatide reduced AHI by 29.3 events per hour compared with 5.5 events per hour on placebo, a treatment difference of 23.8 events per hour (95% CI, −29.6 to −17.9; P<0.001). Expressed as a percentage, tirzepatide reduced AHI by 55.0% in Trial 1 and 62.8% in Trial 2, compared with 5.0% and 6.4% on placebo.
Body weight fell by 18.1% in Trial 1 and 20.1% in Trial 2 with tirzepatide, versus 1.3% and 2.3% on placebo. Blood pressure, hypoxic burden, and inflammatory markers all improved. In secondary analyses, 42.2% of tirzepatide-treated participants in Trial 1 and 50.2% in Trial 2 achieved an AHI of fewer than 5 events per hour or between 5 and 14 events per hour with no daytime sleepiness, thresholds consistent with clinical remission or downstaging of OSA severity.
Side effects and tolerability
The most common adverse events were gastrointestinal, primarily nausea, diarrhea, constipation, and vomiting, and were mostly mild-to-moderate and concentrated during the dose-escalation phase. These are class effects for GIP/GLP-1 receptor agonists. Serious adverse events were uncommon, and no unexpected safety signals emerged. Contraindications and boxed warnings from tirzepatide’s existing labels apply, including a warning about the risk of thyroid C-cell tumors observed in rodent studies.
How the effect size should be read
An AHI drop of 20 to 24 events per hour is a large clinical effect and roughly the same magnitude achieved by CPAP in adherent users. The 42% to 50% clinical-remission rate is meaningful, though it means around half of treated participants still had residual OSA at 52 weeks. Tirzepatide also works gradually. CPAP works from the very first night of use, whereas tirzepatide’s benefit accrues as weight comes down over months. Insurance coverage may differ depending on whether the prescription is written for OSA, obesity, or both, and access remains a real constraint on how many patients can start the drug.
What the evidence cannot yet answer
SURMOUNT-OSA was 52 weeks long. Whether the AHI reductions persist after tirzepatide is stopped is not established. GLP-1 class trials in obesity have shown that most of the weight lost is regained within one year of discontinuation, and OSA severity tracks weight, so durability of the OSA benefit after treatment cessation is a real open question. The trials also enrolled predominantly white participants, and effects in other populations, including those with lower baseline BMI, remain to be characterized. Head-to-head trials against CPAP have not been conducted. Whether tirzepatide changes long-term cardiovascular outcomes, the reason OSA is clinically important, is being tested in ongoing trials.
What the approval settled
The FDA’s December 20, 2024 approval established that reducing weight can be treated as a legitimate mechanism for treating OSA itself, not just its downstream complications. It also reframes how physicians and insurers might think about OSA. Instead of a single-track path centered on CPAP, patients now have a pharmacological option that engages the underlying physiology. The body mass index threshold in the approval (BMI ≥30 kg/m²) matches the trial inclusion criteria, and prescribers are advised to combine tirzepatide with lifestyle intervention and, where appropriate, CPAP or oral appliance therapy rather than substitute for them.
The trial authors concluded that “among persons with moderate-to-severe obstructive sleep apnea and obesity, tirzepatide reduced the AHI, body weight, hypoxic burden, hsCRP concentration, and systolic blood pressure and improved sleep-related patient-reported outcomes.” For a condition affecting nearly a billion adults, with adherence-limited primary therapy for four decades, the arrival of a drug that engages the underlying biology is a substantive addition to the treatment options available.
References
- Malhotra A, Grunstein RR, Fietze I, et al. Tirzepatide for the treatment of obstructive sleep apnea and obesity. New England Journal of Medicine, 2024; 391: 1193-1205. DOI: 10.1056/NEJMoa2404881