GLP-1 Drugs and Sleep Apnoea: The SURMOUNT-OSA Trial Explained

Obstructive sleep apnoea (OSA) is the most common sleep disorder in people with obesity, affecting approximately 40% of obese adults. The connection is mechanical — upper airway fat deposition reduces airway dimensions, increasing collapsibility during sleep.

Weight loss consistently improves OSA severity. GLP-1 drugs produce substantial weight loss. The SURMOUNT-OSA trial formalised whether tirzepatide's weight-loss effect translates to a clinically meaningful improvement in OSA — and whether it was large enough for a drug approval.

This article awaits medical-reviewer signoff.

SURMOUNT-OSA: the trial

Published in the New England Journal of Medicine in 2024, SURMOUNT-OSA was a double-blind RCT of tirzepatide versus placebo in adults with moderate-to-severe OSA (AHI ≥15 events/hour) and obesity (BMI ≥30) over 52 weeks.

The trial had two cohorts:

• Cohort 1: Patients not using CPAP (n=234)
• Cohort 2: Patients using CPAP but wanting to reduce or eliminate it (n=235)

Primary endpoint: Change in AHI (apnoea-hypopnoea index — number of apnoea + hypopnoea events per hour of sleep) from baseline.

Results:

The reductions were clinically large and statistically significant. Secondary outcomes also favoured tirzepatide: improvements in hypoxic burden (oxygen desaturation), sleep disturbance measures, patient-reported outcomes (Epworth Sleepiness Scale), and cardiometabolic markers.

OSA resolution: In Cohort 1 (no CPAP), approximately 42% of tirzepatide patients achieved AHI below 5 events/hour at week 52 — below the diagnostic threshold for any OSA.

Weight loss: Tirzepatide patients lost approximately 18–20% of body weight. The AHI improvement correlated with weight loss magnitude.

The FDA approval

Based on SURMOUNT-OSA, the FDA approved an updated Zepbound (tirzepatide, obesity label) prescribing label in 2024, adding:

Indication: To reduce excess body weight and maintain weight reduction in adults with obesity (initial BMI ≥30 kg/m²) and moderate-to-severe obstructive sleep apnoea.

Zepbound is the first obesity drug with a specifically approved indication for OSA. This opened a new insurance pathway for patients with obesity and OSA who had difficulty getting GLP-1 coverage via the obesity indication alone.

Medicare GLP-1 Bridge implication: The Medicare GLP-1 Bridge (effective July 1, 2026) covers Zepbound for Medicare patients with qualifying conditions — OSA with obesity is one of the qualifying combinations. Patients who previously could not access Medicare coverage for GLP-1s due to the obesity-only indication may now qualify via the OSA pathway.

How GLP-1s improve sleep apnoea

The primary mechanism is weight loss reducing upper airway fat deposition:

• Periglottic (around the throat) and tongue fat decreases
• The upper airway becomes less collapsible during sleep
• Breathing efforts more reliably maintain airway patency

Additional possible mechanisms beyond weight loss:

• Reduced tongue fat (the tongue's fat content is separately associated with OSA severity)
• Reduced inflammation (obesity-associated systemic inflammation may affect upper airway muscle tone)
• Changes in nocturnal fluid redistribution (upper body fluid shifts in supine position contribute to OSA in some patients)

Semaglutide and OSA: the indirect evidence

Semaglutide does not yet have a dedicated OSA indication. The SELECT trial (semaglutide for cardiovascular outcomes in patients with established CVD and obesity but without T2D) enrolled many patients with OSA. SELECT showed cardiovascular risk reduction and improvements in patient-reported sleep quality, but AHI was not the primary measurement tool.

Based on the STEP trials' weight loss magnitude (~15–17%) being modestly less than SURMOUNT-OSA's tirzepatide weight loss (~18–20%), the expectation is that semaglutide also improves OSA meaningfully — just with somewhat less magnitude due to lower average weight loss. No dedicated semaglutide OSA trial equivalent to SURMOUNT-OSA has published.

Implications for OSA patients considering GLP-1 therapy

Who this is most relevant for:

• Patients with obesity-related OSA who are CPAP-intolerant or non-adherent
• Patients who want to explore whether weight loss might reduce or eliminate their CPAP requirement
• Medicare patients with OSA as a qualifying condition for the GLP-1 Bridge

What to discuss with your prescriber:

• Which drug: Zepbound now has the specific OSA indication; Wegovy does not
• CPAP continuation: Do not discontinue CPAP without a repeat sleep study confirming OSA has resolved or significantly improved — OSA on drug-suppression is not the same as structurally resolved OSA
• Monitoring: A follow-up sleep study after significant weight loss (6–12 months into treatment) is appropriate to re-evaluate OSA severity

Editorial note: This article awaits medical-reviewer signoff. OSA management requires coordination between the prescriber managing GLP-1 therapy and a sleep medicine provider who can re-evaluate OSA status and guide CPAP decisions.