SURMOUNT-OSA: tirzepatide for obstructive sleep apnea with obesity

SURMOUNT-OSA is the trial behind the sleep-apnea indication for tirzepatide. Its primary endpoint is not weight; it is breathing.

What the trial asked

Whether tirzepatide reduces the severity of moderate-to-severe obstructive sleep apnea in adults with obesity, both in people not using positive airway pressure (PAP) and in people already using it.

Design

Two phase 3, double-blind, randomised, placebo-controlled trials run under one protocol. Trial 1 enrolled people not on PAP at baseline; trial 2 enrolled people on PAP. In each, participants were assigned 1:1 to tirzepatide at maximum tolerated dose (10 or 15 mg) or placebo, once weekly for 52 weeks.

Who was enrolled

Adults with moderate-to-severe obstructive sleep apnea and obesity. Baseline mean apnea-hypopnea index (AHI) was 51.5 events per hour in trial 1 and 49.5 in trial 2; mean BMI was 39.1 and 38.7. The abstract does not state how many were randomised. The safety table in the PMC author manuscript lists 114 tirzepatide and 120 placebo participants in trial 1, and 119 and 114 in trial 2, which is 467 in total who received a dose.

Primary endpoint and result

Primary endpoint: change in AHI from baseline to week 52.

P less than 0.001 in both trials. Units are events per hour of sleep.

Key secondary results

The abstract lists the key multiplicity-controlled secondary endpoints: percent change in AHI, percent change in body weight, hypoxic burden, patient-reported sleep impairment and disturbance, high-sensitivity CRP, and systolic blood pressure. It states that all improved significantly with tirzepatide versus placebo. It does not give the numbers, including the weight change, so this digest does not either.

Adverse events and discontinuation

Gastrointestinal events were the most frequently reported adverse events with tirzepatide, mostly mild to moderate. From the safety table in the PMC author manuscript: adverse events led to discontinuation of the trial drug in 5 of 114 (4.4 percent) versus 2 of 120 (1.7 percent) in trial 1, and 4 of 119 (3.4 percent) versus 8 of 114 (7.0 percent) in trial 2. Serious adverse events: 7.9 versus 5.8 percent (trial 1) and 5.9 versus 10.5 percent (trial 2). No deaths.

Funding and registration

Eli Lilly. ClinicalTrials.gov NCT05412004.

What this trial does not show

• It does not separate the effect of weight loss from any direct effect of the drug on airway physiology.
• Participants had obesity. It says nothing about sleep apnea in people of normal weight.
• AHI is a laboratory measure. The trial was not designed to show fewer cardiovascular events or fewer road accidents.
• The abstract does not report the weight change, so the common shorthand "and they lost X percent" cannot be sourced from it.

Where the numbers come from

PubMed abstract (PubMed 38912654) and the PMC author manuscript (PMC11598664), fetched 4 September 2026. For how an obesity drug came to be studied in a breathing disorder, the sibling site The Science covers the mechanism side.