The effects of exercise training as a treatment component of obstructive sleep apnea in diverse patient groups: current understanding and focus areas

It has been established that exercise is an essential component of obstructive sleep apnea (OSA) treatment. However, despite ongoing research and important findings reported in the last decade,^1–17 the effects of exercise on patients with OSA remain insufficiently understood. It is not fully clear whether certain subgroups would benefit more from exercise therapy than others, and whether certain types of exercise would be more beneficial than others.

In this issue of the Journal of Clinical Sleep Medicine, Lin et al investigated the therapeutic effects of exercise in patients with OSA, aiming to identify the subgroups that benefit the most and determine the optimal exercise protocol.¹ In their meta-analysis, exercise significantly reduced the apnea-hypopnea index (AHI), Epworth Sleepiness Scale, and body mass index, and enhanced peak oxygen uptake (VO2peak) in patients with OSA. In continuous positive airway pressure (CPAP)-adherent patients, exercise significantly improved VO2peak, whereas it did not provide additional benefits in AHI and Epworth Sleepiness Scale reductions. Combined resistance training and aerobic exercise resulted in a trend of greater AHI reduction and significant VO2peak enhancement. Notably, the baseline AHI and body mass index did not affect the impact of exercise training on OSA. Therefore, Lin et al concluded that exercise, including resistance and aerobic training, should be part of treatment for patients with OSA of all severities, irrespective of obesity status, as well as for patients who are already under CPAP.

A study by Sengul et al² assessed the effect of breathing and physical exercise on pulmonary functions, AHI, and quality of life (QoL) in patients with OSA. Interestingly, exercise appeared not to alter anthropometric characteristics and respiratory functions while improving AHI, health-related QoL, sleep quality (SQ), and exercise capacity in patients with mild to moderate OSA. Building upon these findings, a randomized controlled trial by Kline et al³ evaluated the efficacy of a training program for reducing OSA severity and improving SQ, and explored possible mechanisms through which exercise may reduce OSA severity. Measurements of SQ included laboratory polysomnography before and following the intervention, actigraphy, and the Pittsburgh Sleep Quality Index. The authors concluded that exercise training had moderate treatment efficacy for the reduction of AHI in sedentary overweight and obese adults, suggesting that exercise may be beneficial for the management of OSA beyond simply facilitating weight loss.

OSA has various systemic consequences that can increase cardiovascular morbidity and mortality as well as increase health care expenditure, making OSA an important public health concern.^4,5 Another meta-analysis was conducted by Iftikhar et al⁴ to analyze the data from studies (through PubMed and Embase) showing a favorable effect of supervised exercise training on the severity of OSA (primary outcome) in adults. This meta-analysis showed a statistically significant effect of exercise in reducing the severity of OSA in patients with minimal changes in body weight. In addition, the significant effects of exercise on cardiorespiratory fitness, daytime sleepiness, and sleep efficiency indicate the potential value of exercise in the management of OSA. A review by Torres-Castro et al⁵ discussed the rationale and effects of using general physical exercise, oropharyngeal exercises, and respiratory muscle training as an adjunctive treatment for patients with OSA. Overall, the recommended treatment for OSA is the use of CPAP, which is a therapy that prevents apnea events by keeping the airways open.

OSA is difficult to manage for those who are intolerant or nonadherent with standard facial mask treatment options. Current treatment options do not address the underlying cause of OSA, with exercise as an additional treatment option to improve OSA indices. Aiello et al⁶ studied the efficacy of exercise on AHI in adult patients with OSA through a systematic review and meta-analysis. Overall, among adult patients with OSA, exercise as the sole intervention was associated with improved clinical outcomes. Silva et al⁷ investigated the extent to which exercise is associated with symptoms in patients with severe OSA. Nonexercisers and exercisers differed significantly in terms of obesity, the mean proportion of sleep in non-rapid eye movement stage 3 sleep, and tiredness. Nonexercisers had a higher symptom frequency/scores and poorer SQ. It was concluded that exercise is associated with lower frequency and intensity of symptoms in patients with severe OSA. Van Offenwert et al⁸ also showed that low levels of physical activity are associated with higher odds of OSA. It was reported that a regular and predominantly aerobic exercise training significantly reduced OSA severity, even without a significant decrease in body weight.

With exercise being more frequently utilized in treatment for OSA, Peng et al⁹ performed a systematic review of the intervention efficacy of exercise on OSA. Compared with the control group, exercise helped improve the AHI, minimum oxygen saturation, VO2peak, and Pittsburgh Sleep Quality Index. It was concluded that exercise reduces OSA severity with no changes in body mass index, and the effect of aerobic exercise combined with resistance training is better than aerobic exercise alone in AHI reduction. Exercise also improves cardiopulmonary fitness, SQ, and excessive daytime sleepiness.

As studies assessing the potential benefit of exercise on cardiac autonomic activity in these patients are limited, Berger et al¹⁰ evaluated potential improvement in cardiac autonomic function measured through heart rate variability physical activity program in patients with OSA. Overall, supervised community physical activity may prevent a decline in nighttime cardiac autonomic function observed in nontreated community-dwelling patients with moderate OSA. Thus, beyond AHI improvement, exercise may be cardioprotective in patients with OSA through bradycardia, cardiac autonomic function preservation, and VO2peak increase.

Ackel-D’Elia et al¹¹ evaluated the effects exercise training associated with CPAP treatment on the self-reported and objective sleep measurements, QoL, and mood in moderate to severe patients with OSA. Overall, exercise training associated with CPAP treatment for patients with OSA has a positive impact on self-reported daytime sleepiness, QoL (physical functioning and general health perception), and mood state (tension and fatigue). Expanding upon these results, Lins-Filho et al¹² investigated the effect of exercise training on QoL, daytime sleepiness, and SQ in adults with OSA by summarizing the results of clinical trials obtained through a systemic review of databases. Exercise training significantly improved QoL and SQ, and reduced daytime sleepiness. Thus, physical exercise training was effective in improving self-reported parameters and reducing the severity of OSA.

As studies on the effects of a comprehensive exercise program on patients with OSA in a community setting remain limited, Torres-Castro et al¹³ investigated the effects of a combined physical and oropharyngeal exercise program on the AHI in patients with moderate to severe OSA. Although a comprehensive multimodal program does not modify the AHI, it can reduce body weight and increase the walking distance of patients with moderate to severe OSA. Ueno et al¹⁴ tested the effects of exercise training on sleep and neurovascular control in patients with systolic heart failure with and without sleep-disordered breathing. The beneficial effects of exercise training on neurovascular function, functional capacity, and QoL in patients with systolic dysfunction and heart failure were shown to occur independently of sleep-disordered breathing. Exercise training decreases the severity of OSA but does not affect CSA in patients with heart failure and sleep-disordered breathing.

OSA is prevalent among older individuals and is linked to increased cardiovascular disease morbidity. A study by Dobrosielski et al¹⁵ examined the change in OSA severity following exercise training and dietary induced weight loss in older adults and the association between the changes in OSA severity, body composition, and aerobic capacity with arterial distensibility. Collectively, the severity of OSA was reduced following an exercise and weight loss program among older adults, suggesting that this lifestyle approach may be an effective first line nonsurgical and nonpharmacological treatment for older patients with OSA. Araújo et al¹⁶ evaluated the effects of exercise training on the POMS, heart rate variability, spontaneous baroreflex sensitivity, and sleep disturbance severity in patients with OSA. Improved sleep parameters, fatigue, and cardiac autonomic modulation were observed, with exercise training being a likely protective factor against the deleterious effects of hypoxia on these components in patients with OSA. Mendelson et al¹⁷ performed a systematic review to assess the objective physical activity levels of patients with OSA and explored the effects of exercise training on OSA severity, body mass index, sleepiness, and cardiorespiratory fitness (VO2peak). It was concluded that interventions focusing on increasing physical activity levels, such as exercise training, may have important clinical impacts on both OSA severity and the burden of associated comorbidities.

In conclusion, future studies as well as treatments administered and prescribed should consider the objective measurement of physical activity in routine OSA management. Well-designed clinical trials should be performed to advance the existing knowledge. Studies often exhibit high heterogeneity regarding patient characteristics and intervention design. These limitations hinder meta-regression and further subgroup analyses based on parameters such as frequency, intensity, and length of exercise session. Another aspect to consider is that only a few of the currently published studies were conducted after the COVID-19 pandemic. Thus, the impact of COVID-19 on OSA has not been comprehensively evaluated and would need to be addressed by future studies. Based on previous studies,¹³ patients younger than 60 may also present a decreased AHI after intervention; however, this requires further study.

Overall, further investigations are also required to determine the optimal frequency, intensity, duration, and combination of exercise interventions for OSA, and additional randomized clinical trials should be performed to confirm the current clinical findings. The intricate relationships between physical activity, exercise, and OSA as well as the efficacy of exercise as alternative or additional treatment for OSA must be understood to optimize treatment.

DISCLOSURE STATEMENT

The author declares that no known competing financial interests, personal relationships, or connections exist that may have influenced this commentary.