A meta-analysis of 14 studies with 1,273 participants found that long-term CPAP therapy (≥24 weeks) significantly reduced insulin resistance in patients with obstructive sleep apnoea and type 2 diabetes, but did not improve key blood sugar markers like HbA1c.
- Long-term CPAP use (≥24 weeks) improved insulin resistance but not blood sugar levels
- Medium and long-term CPAP reduced daytime sleepiness but increased BMI
- Treatment duration matters: benefits varied based on how long patients used CPAP
How this compares to prior research
Previous research has established that obstructive sleep apnoea is common in patients with type 2 diabetes and may worsen metabolic control. While CPAP therapy is the standard treatment for sleep apnoea, its effects on diabetes outcomes have been inconsistent across studies. The relationship between treatment duration and metabolic benefits remained unclear, with individual trials showing mixed results for blood sugar control.
Obstructive Sleep Apnoea Prevalence, Global, 1990–1999
Key findings
- Long-term CPAP therapy (≥24 weeks) reduced insulin resistance (HOMA-IR) by 1.67 points compared to control groups
- CPAP therapy did not significantly change HbA1c, fasting blood glucose, or mean blood glucose levels regardless of duration
- Medium-term (12-24 weeks) and long-term CPAP reduced daytime sleepiness scores and increased BMI by 0.31-0.74 kg/m²
What this means in practice
- Discuss with your doctor whether long-term CPAP therapy could help manage insulin resistance if you have both sleep apnoea and diabetes
- Monitor your weight if starting CPAP therapy, as modest BMI increases were observed in studies
- Set realistic expectations: CPAP may improve insulin resistance and sleepiness but likely will not lower your HbA1c levels
Frequently asked questions
Does CPAP therapy help control blood sugar in diabetics with sleep apnoea?
CPAP therapy improves insulin resistance with long-term use but does not significantly reduce HbA1c or blood glucose levels in patients with both conditions.
How long do you need to use CPAP to see benefits for diabetes?
Benefits for insulin resistance appear after at least 24 weeks of CPAP use. Improvements in sleepiness can occur after 12 weeks of treatment.
Does CPAP therapy cause weight gain in diabetic patients?
Yes, CPAP therapy was associated with modest BMI increases of 0.31-0.74 kg/m² after 12 weeks or more of use in this patient population.
Key terms explained
HOMA-IR
Homeostasis Model Assessment of Insulin Resistance Index, a measure of how well the body responds to insulin
HbA1c
Haemoglobin A1c, a blood test showing average blood sugar levels over the past 2-3 months
CPAP
Continuous positive airway pressure, a machine that delivers pressurised air through a mask to keep airways open during sleep
Source: Effects of continuous positive airway pressure therapy duration on patients with obstructive sleep apnoea and type 2 diabetes mellitus: a systematic review and meta-analysis. · DOI: doi: 10.1136/bmjresp-2025-003324