Obstructive sleep apnea, CPAP therapy, and gastroesophageal reflux symptoms: evidence from a prospective cohort study

Background Obstructive sleep apnea (OSA) frequently coexists with gastroesophageal reflux disease (GERD), yet the degree to which hypoxic burden contributes to reflux severity and whether symptoms improve with continuous positive airway pressure (CPAP) remains insufficiently defined. Objective: To investigate the cross-sectional associations of OSA severity and nocturnal hypoxic burden with GERD symptom presence and severity, and to evaluate longitudinal changes in reflux symptoms after CPAP therapy in a prospective follow-up cohort. Methods In a prospective cohort of adults undergoing polysomnography, 580 participants were evaluated at baseline and stratified by GERD status using the GERD-Q (≥8 indicating GERD). OSA severity (apnea–hypopnea index, AHI) and nocturnal hypoxemia burden (T90%, minimum SpO₂, oxygen desaturation index) were compared across reflux strata. Multivariable linear and logistic regression models assessed continuous associations between sleep parameters and GERD severity. A CPAP sub-cohort of moderate-to-severe OSA with concomitant reflux ( n  = 150; completed follow-up, n  = 112) was monitored for GERD-Q changes at 3 and 6 months. Results GERD prevalence reached 29.0%. GERD-Q scores demonstrated dose–response escalation across both OSA severity and hypoxemia categories ( p for trend <0.001). T90% and ODI showed stronger associations with reflux burden than AHI in fully adjusted models (T90% β  = 0.81; ODI β  = 0.44; both p  < 0.001), while minimum SpO₂ remained inversely related ( β  = −0.18; p  = 0.003). Logistic models confirmed increased GERD risk in moderate (OR = 1.87) and severe OSA (OR = 2.74), and in patients with marked nocturnal hypoxemia (T90 > 10%; OR = 3.42; all p  < 0.001). CPAP therapy yielded progressive symptom reduction (GERD-Q − 1.92 at 3 months; −3.28 at 6 months), with clinically meaningful improvement in 69.6% at 6 months. Conclusion OSA severity and nocturnal desaturation jointly predict reflux symptom burden, with hypoxic load outperforming event frequency. CPAP produced sustained GERD symptom improvement over 6 months.