Key points
- Obstructive sleep apnoea (OSA) affects an estimated 1.5 million adults in the UK and is strongly linked to obesity
- The SURMOUNT-OSA trial showed tirzepatide reduced apnoea-hypopnoea index (AHI) by approximately 25 to 30 events per hour compared with placebo
- Up to 43 per cent of participants on tirzepatide achieved an AHI below 5, effectively resolving their sleep apnoea
- The FDA has approved tirzepatide for moderate-to-severe OSA in adults with obesity; MHRA review is anticipated
- GLP-1 therapy may complement or, in some cases, replace CPAP for eligible patients
Understanding obstructive sleep apnoea
Obstructive sleep apnoea is a condition in which the muscles and soft tissues in the throat repeatedly collapse during sleep, partially or completely blocking the upper airway. Each episode (an apnoea or hypopnoea) reduces oxygen levels and disrupts sleep, often without the person being fully aware.
OSA is classified by the apnoea-hypopnoea index (AHI), which counts the number of breathing interruptions per hour of sleep:
- Mild: AHI 5 to 14 events per hour
- Moderate: AHI 15 to 29 events per hour
- Severe: AHI 30 or more events per hour
The link between obesity and OSA
Obesity is the single strongest risk factor for obstructive sleep apnoea. Excess fat deposits around the neck and upper airway narrow the pharyngeal space, making collapse more likely during sleep. Abdominal obesity also reduces lung volume, which decreases the traction forces that help keep the airway open.
Research shows that approximately 60 to 70 per cent of people with OSA are overweight or obese. For every increase of one unit in BMI, the risk of developing OSA increases by approximately 14 per cent. Conversely, weight loss is one of the most effective treatments: a 10 per cent reduction in body weight reduces the AHI by approximately 26 per cent on average.
Current treatment in the UK
The standard first-line treatment for moderate-to-severe OSA in the United Kingdom is continuous positive airway pressure (CPAP) therapy. CPAP works by delivering a constant stream of pressurised air through a mask worn during sleep, which splints the airway open and prevents collapse.
Limitations of CPAP
While CPAP is highly effective when used correctly, adherence remains a significant challenge. Studies consistently show that 30 to 50 per cent of patients prescribed CPAP do not use it for the recommended minimum of four hours per night. Common complaints include mask discomfort, claustrophobia, nasal congestion, dry mouth and noise disturbance to bed partners.
For patients who cannot tolerate CPAP, alternatives include mandibular advancement devices, positional therapy and, in selected cases, upper airway surgery. However, none of these alternatives addresses the underlying cause in the majority of patients: excess weight.
The SURMOUNT-OSA trial
The SURMOUNT-OSA programme comprised two randomised, double-blind, placebo-controlled trials evaluating tirzepatide in adults with moderate-to-severe obstructive sleep apnoea and obesity. Published in the New England Journal of Medicine, the trial results represented a landmark moment for the treatment of OSA.
Trial design
- Participants: Adults with BMI of 30 or above and moderate-to-severe OSA (AHI of 15 or more)
- SURMOUNT-OSA 1: Patients not using CPAP at baseline
- SURMOUNT-OSA 2: Patients using CPAP at baseline
- Treatment: Tirzepatide (maximum tolerated dose up to 15 mg weekly) versus placebo
- Duration: 52 weeks
- Primary endpoint: Change in AHI from baseline
Key results
| Outcome | Tirzepatide | Placebo |
|---|---|---|
| AHI reduction (SURMOUNT-OSA 1) | Approximately −25 events/hour | Approximately −5 events/hour |
| AHI reduction (SURMOUNT-OSA 2) | Approximately −30 events/hour | Approximately −6 events/hour |
| AHI below 5 (disease resolution) | Up to 43% | Approximately 14% |
| Body weight reduction | Approximately 18 to 20% | Approximately 1.5 to 2% |
| Improvement in daytime sleepiness (ESS) | Significant improvement | Modest improvement |
| Systolic blood pressure reduction | Approximately −7 to −10 mmHg | Approximately −1 to −2 mmHg |
What these numbers mean: A reduction of 25 to 30 events per hour is clinically transformative. A patient with severe OSA (AHI 40) could see their score drop to mild or even normal levels. Nearly half of participants on tirzepatide achieved an AHI below 5, meaning their sleep apnoea had effectively resolved.
How GLP-1 medications improve sleep apnoea
The benefits of GLP-1 therapy for obstructive sleep apnoea are primarily driven by weight loss, but there may be additional mechanisms at play.
Weight-loss-dependent mechanisms
- Reduced neck fat: Weight loss reduces the fat deposits around the pharynx that compress the upper airway during sleep
- Reduced abdominal fat: Lower abdominal pressure improves lung volumes, increasing the traction forces that stabilise the airway
- Reduced tongue fat: Research has shown that tongue fat volume is an independent predictor of OSA severity, and weight loss reduces it
- Improved muscle function: Reduced inflammatory burden may improve the neuromuscular control of upper airway dilator muscles
Potential weight-loss-independent effects
- Reduced systemic inflammation: GLP-1 agonists reduce pro-inflammatory markers that contribute to upper airway oedema
- Improved fluid distribution: Better metabolic control may reduce the nocturnal fluid shift from legs to the neck that worsens OSA
- Cardiovascular benefits: Reduced blood pressure and improved cardiac function may independently improve sleep quality
CPAP versus GLP-1 medication: a comparison
| Factor | CPAP therapy | GLP-1 medication |
|---|---|---|
| Mechanism | Mechanically splints airway open | Reduces airway obstruction through weight loss |
| Speed of effect | Immediate, from the first night | Gradual over months as weight decreases |
| AHI reduction | Eliminates events during use | 25 to 30 events/hour reduction at 52 weeks |
| Adherence | 30 to 50% poor adherence | Weekly injection; generally well tolerated |
| Addresses root cause | No (symptomatic relief only) | Yes (reduces obesity, the primary risk factor) |
| Additional health benefits | Limited to OSA symptom relief | Cardiovascular, metabolic, hepatic and renal benefits |
| NHS availability | Widely available | Currently for obesity/diabetes; OSA indication pending |
Complementary approaches: For many patients, the optimal strategy may be to use CPAP for immediate symptom relief while simultaneously taking a GLP-1 medication to achieve weight loss. Over time, as weight decreases and the AHI improves, it may be possible to reduce or discontinue CPAP under medical supervision.
Quality of life improvements
Beyond the AHI numbers, participants in the SURMOUNT-OSA trial reported meaningful improvements in quality of life. Obstructive sleep apnoea causes daytime sleepiness, impaired concentration, mood disturbance and reduced work productivity. Partners are also affected by snoring and observed apnoeas.
Tirzepatide-treated participants reported:
- Significant reduction in daytime sleepiness as measured by the Epworth Sleepiness Scale
- Improved sleep quality and reduced nocturnal awakenings
- Better physical functioning and less fatigue
- Reduced snoring frequency and intensity
- Improvements in mood and mental health scores
UK treatment pathway and access
In the United Kingdom, obstructive sleep apnoea is typically diagnosed and managed through NHS sleep centres. Referral is usually made by a GP based on symptoms (daytime sleepiness, witnessed apnoeas, loud snoring) and screening questionnaires.
Current pathway
- GP assessment and screening (STOP-BANG or Epworth Sleepiness Scale)
- Referral to NHS sleep service for home sleep study or polysomnography
- CPAP prescription for moderate-to-severe OSA
- Follow-up at 1 month, 3 months and annually
Where GLP-1 therapy fits in
Patients with both obesity and OSA may be eligible for GLP-1 therapy through NHS specialist weight management services or through private prescribers. If the MHRA approves tirzepatide specifically for OSA, this could create a dedicated prescribing pathway that integrates sleep medicine with weight management.
Important: Do not stop or reduce CPAP therapy without consulting your sleep specialist. Even if you are losing weight with a GLP-1 medication, CPAP provides immediate protection against airway obstruction. A repeat sleep study should be performed before any changes to CPAP use are considered.
Semaglutide and sleep apnoea
While the SURMOUNT-OSA trial used tirzepatide, there is also evidence supporting the role of semaglutide in improving sleep apnoea. The STEP programme trials consistently demonstrated improvements in sleep-related outcomes as secondary endpoints. Any significant weight loss achieved through GLP-1 therapy is likely to improve OSA severity.
The key difference is that tirzepatide, as a dual GLP-1/GIP receptor agonist, achieves greater weight loss on average than semaglutide alone (approximately 20 to 22 per cent versus 15 to 17 per cent). For patients with severe OSA requiring maximum weight reduction, this difference may be clinically relevant.