Small real-world study raises a CPAP adherence question when tirzepatide is added

A small study out of the University of Rome Tor Vergata, published February 27, 2026 in the journal Diabetes, Obesity and Metabolism, compared tirzepatide plus continuous positive airway pressure (CPAP) against CPAP alone in patients with obstructive sleep apnea and obesity ^[1]. The combination group lost significantly more weight and showed better control of sleep apnea and daytime sleepiness than the CPAP-only group ^[1]. But the study also turned up a smaller, harder-to-explain finding: fewer patients in the tirzepatide-plus-CPAP group kept using their CPAP machine regularly.

At six months, 60% of patients on tirzepatide plus CPAP were still adherent to CPAP therapy, compared with 90% of patients using CPAP alone, the researchers reported ^[1]. With only 20 patients total split between groups, that 30-percentage-point gap did not reach statistical significance ^[1]. Still, the researchers noted the pattern lines up with a signal that has already shown up in larger, claims-based data from the United States, where patients starting GLP-1 or dual GLP-1/GIP therapy for sleep apnea appear less likely to stick with CPAP over time ^[1].

Tirzepatide, sold in the US as Mounjaro for type 2 diabetes and Zepbound for weight management, already carries backing for use in obstructive sleep apnea. A large trial published in 2024 in the New England Journal of Medicine found tirzepatide improved sleep apnea severity in people with obesity, and the FDA has approved a tirzepatide-based medication specifically for obstructive sleep apnea ^[1]. The new Italian study builds on that evidence by testing what happens when tirzepatide is layered on top of CPAP, the long-standing standard treatment for the condition, rather than compared against it head-to-head.

The study also looked at daytime sleepiness and cognitive performance, finding improvements in the tirzepatide group beyond what CPAP alone produced, according to the researchers ^[1]. But because the sample was so small, the authors treat the adherence finding as a signal worth watching rather than a settled result ^[1].

Why it matters for patients

CPAP remains the frontline treatment for obstructive sleep apnea because it works while the mask is on, every night. If adding a GLP-1/GIP drug like tirzepatide leads some patients to loosen up on CPAP use, that could offset some of the drug's own benefits for sleep apnea, since weight loss reduces apnea severity but does not eliminate it for everyone. Patients weighing tirzepatide alongside CPAP may want to know that this open question exists, even though this particular study is too small to prove a real drop-off in adherence occurs, or why it might happen ^[1].

The study does not explain the mechanism behind the adherence gap. It is not yet known whether patients felt less need for CPAP as they lost weight and symptoms improved, whether side effects of tirzepatide played a role, or whether the difference in this small sample was simply chance ^[1].

What happens next

The authors call for larger, longer trials to determine whether the CPAP adherence drop seen here — and in the separate US claims data they cite — is a real and consistent effect of combining tirzepatide with CPAP, or a statistical fluke tied to small study size ^[1]. No dates for such follow-up trials are given in the published research letter ^[1].