Original ArticleCPAP therapy improves erectile function in patients with severe obstructive sleep apnea
Introduction
Obstructive sleep apnea (OSA) has been found to be linked to erectile dysfunction (ED). Thus, an increased prevalence of ED as well as an independent association with the extent of nocturnal hypoxia have been reported in patients with OSA [1], [2], [3], [4], [5]. Within this context, increased oxidative stress with reduced bioavailability of nitric oxide (NO) and blunted vasodilation is considered an important pathophysiological mechanism [6], [7], [8]. Increased levels of catecholamines and endothelin or decreased testosterone may also be factors [9], [10], [11]. Additional causative factors may be sleep fragmentation, reduced amounts of REM sleep and daytime sleepiness or impaired vigilance [12], [13]. Finally, neural abnormalities such as prolonged bulbocavernosus reflex latency may contribute to the development of ED in OSA [14].
Some studies have already suggested that CPAP therapy may improve erectile function in affected patients [15], [16], [17], [18], [19], [20], [21], [22]. However, most of these studies had methodological drawbacks, eg, low patient numbers, retrospective design and short-time therapeutic intervention. Furthermore, all prior studies did not focus on the patients most likely to gain a benefit from CPAP, ie, those with severe OSA, and did not perform sleep studies at follow-up.
Against this background, we aimed to perform a prospective study on the long-term effects of CPAP therapy on erectile function in a larger number of patients with severe OSA. In addition, we thought to address the roles of daytime sleepiness, reduced quality of life and depression within this context. This is relevant as these factors represent well established clinical features of OSA and may independently contribute to the emergence of ED.
Section snippets
Patient recruitment and assessment
The patients of the present study were prospectively recruited at centers affiliated with the German Sleep Apnea Research Network (GERSAN). They had been admitted to the sleep lab for suspected sleep apnea as judged by clinical symptoms and the results of home-based polygraphy. All of them were between 18 and 80 years old and had a diagnosis of severe OSA as verified by full-night attended polysomnography (ie, an apnea-hypopnea-index [AHI] ≥ 30 per hour of sleep). Furthermore, all study
Patient characteristics
The mean age of the 94 men who completed the study was 51.5 ± 0.9 years and their mean BMI was 34.2 ± 0.6 kg/m2 indicating WHO class I obesity. Based on the inclusion criteria of the study, polysomnography had revealed severe OSA in all subjects with a mean AHI exceeding 50/h. About two thirds of the patients suffered from arterial hypertension and approximately one fourth from metabolic disease (ie, hyperlipidemia and diabetes). One third of the patients were smokers and a similar percentage
Discussion
The main results of the present study performed in men with severe OSA were that ED was highly prevalent and that long-term CPAP therapy improved erectile function in most seriously affected patients.
ED was observed in about two thirds of the patients investigated. This is in accordance with prior studies evaluating the prevalence of ED in patients with OSA [1], [2], [3], [4], [5]. Overall, sleep study parameters were similar in patients with varying severities of ED and those with normal
Limitations
Our study has some limitations. First, it may be suspected that a bias was introduced by the large number of patients who were lost to follow-up or had incomplete data sets. However, this is unlikely as the characteristics of these drop-outs were quite similar when compared with the patients finally included in our study. Second, objective determinations of erectile function such as by measuring nocturnal penile tumescence were not attempted. Third, we did not perform polysomnography at
Conclusions
In summary, ED is very frequent in men with severe OSA and can at least partly be reversed by long-term CPAP therapy in most seriously affected patients. The beneficial effect on erectile function may depend on CPAP compliance and is accompanied by improvements of quality of life. Randomized controlled trials are needed to confirm these findings.
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