Effects of moderate- and high-intensity inspiratory muscle training in individuals with obstructive sleep apnea:Systematic review and meta-analysis

Abstract

Introduction: Obstructive sleep apnea (OSA) is the most prevalent sleep-related breathing disorder and is considered a public health concern due to its association with increased cardiovascular morbidity and mortality. Inspiratory muscle training (IMT) has emerged as a promising adjunctive intervention for OSA, potentially reducing disease severity through improvements in respiratory muscle strength and endurance. Objective: To analyze, through a systematic review and meta-analysis, the effects of different IMT intensities on maximal inspiratory pressure (MIP), apnea–hypopnea index (AHI), Pittsburgh Sleep Quality Index (PSQI), and Epworth Sleepiness Scale (ESS), and to describe findings related to forced expiratory volume in the first second (FEV₁) and cardiopulmonary exercise performance (VO₂max) in adults with OSA. Methods: Randomized controlled trials (RCTs) involving adults with OSA undergoing IMT were included. Nine databases were searched using predefined descriptors. Two independent reviewers performed study selection, data nextraction, and risk-of-bias assessment using the Cochrane RoB 2 tool. Meta-analysis was conducted using RevMan 5.4, and certainty of evidence was assessed using the GRADE framework. Subgroup analyses were performed according to IMT intensity. Results: Of the 594 records identified, seven RCTs met the eligibility criteria. Studies included participants with OSA across all AHI severity levels, with IMT as the primary intervention. IMT significantly increased MIP (d = 1.698; 95% CI: 0.182 to 3.214; p = 0.035) and improved sleep quality (PSQI: d = −0.636; 95% CI: −1.133 to −0.139; p = 0.012) and daytime sleepiness (ESS: d = −0.629; 95% CI: −1.043 to −0.215; p = 0.003), with more consistent effects observed in moderate-intensity protocols. No significant effect was found for AHI (d = 0.406; 95% CI: −0.687 to 1.499; p = 0.528). Cardiorespiratory fitness (VO₂max) was assessed in three studies; however, quantitative synthesis was not performed due to the limited number of studies and protocol heterogeneity. Conclusions: IMT appears to be effective in improving inspiratory muscle strength, sleep quality, and daytime sleepiness in adults with OSA, particularly when moderate-intensity protocols are applied. Although effects on AHI remain inconclusive and evidence regarding aerobic capacity is limited, these findings support IMT as a potential adjunctive therapeutic strategy in OSA management and highlight the need for further well-designed trials with standardized protocols.