COPD-OSA Overlap Syndrome

Understanding Overlap Syndrome

“Overlap syndrome” refers to the co-occurrence of obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD). This combination is associated with worse outcomes than either condition alone, including increased cardiovascular risk and poorer quality of life.

Despite its significance, OSA–COPD overlap remains under-recognised in routine respiratory care. Prevalence estimates vary widely (1–10%) due to differences in diagnostic methods, definitions, and patient populations. Identifying and treating this condition early can help improve outcomes and reduce complications.

Consequences

Patients with overlap syndrome often experience:

  • More severe respiratory symptoms

  • Increased daytime sleepiness and fatigue

  • Lower oxygen levels during sleep

  • Higher risk of hypertension and type 2 diabetes

  • More frequent hospitalisations and COPD exacerbations

  • Increased mortality and healthcare burden

Overlap can also reduce daytime oxygen saturation and lead to more acute exacerbations and comorbidities compared to those with COPD or OSA alone.

Risk Factors

The most common risk factors include:

  • Smoking – a shared cause of both COPD and OSA, promoting inflammation and oxidative stress

  • Obesity – especially neck and truncal obesity, which can impact both airway function and lung mechanics

  • Reduced respiratory muscle strength – leading to ventilation-perfusion mismatch and hypoventilation

These factors contribute to nocturnal oxygen desaturation and worsening of both conditions when combined.

Screening & Diagnosis

To assess OSA and nocturnal hypoventilation in overlap syndrome, respiratory polygraphy is recommended—either at home or in hospital. This can help determine the severity of the condition and guide treatment.

Transcutaneous CO₂ monitoring may also be useful alongside respiratory polygraphy, particularly to:

  • Confirm the presence of nocturnal hypoventilation

  • Measure the severity of hypercapnia

  • Distinguish between the contributions of COPD and OSAHS

It’s important that the patient has stable COPD (no recent exacerbations) before diagnosis can be confirmed.

Treatment

Treatment decisions depend primarily on the patient’s arterial carbon dioxide (PaCO₂) levels when awake and asleep.

  • CPAP is the primary therapy for OSA and may be appropriate if the patient has a confirmed diagnosis and PaCO₂ ≤ 7.0 kPa.

  • Non-invasive ventilation (NIV) may be required for patients with more severe COPD and higher levels of daytime or nocturnal hypercapnia.

In patients with modest hypercapnia and no recent exacerbations, the benefit of NIV is less clear and should be evaluated on a case-by-case basis.

References

    1. Bouloukaki I, Fanaridis M, Testelmans D, Pataka A, Schiza S. Overlaps between obstructive sleep apnoea and other respiratory diseases. Breathe. 2022;18(3).

    2. Rajesh S, Wonderling D, Simonds AK. OSA/HS and obesity hypoventilation syndrome in over 16s: NICE guidance summary. BMJ. 2021;375.

    3. Suri TM, Suri JC. Therapies for overlap syndrome of OSA and COPD. FASEB BioAdvances. 2021;3(9):683–93.

    4. Bouloukaki I et al. Overlaps between OSA and other respiratory diseases. Breathe. 2022;18(3).

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