We sent patients from our public sleep apnea clinic to three private clinics for CPAP initiation via voucher use. The success rate of CPAP therapy initiation at 1 year was very high (94%). This is significantly higher than that of our public center, which reported a success rate between 65 and 67% at 1 year [8, 9]. This difference may be related to two significant factors. First, the patients selected for voucher use did not have significant comorbidities, low cognitive capacity, or communication difficulties; these may influence CPAP success rate. Secondly, our criteria for CPAP initiation were recently focused on moderate-to-severe sleep apnea; before 2017 we also treated patients with mild sleep apnea. Balakrishnan et al. reported a significant positive correlation between sleep apnea severity index and CPAP device use, i.e., patients with mild sleep apnea are prone to use their CPAP device significantly less than patients with moderate-to-severe sleep apnea [10]. Moreover, Simon-Tuval T et al. reported that patients with better socioeconomic status had better CPAP outcomes [11]. In Finland, the private sector attracts primarily wealthy patients; in this study, we selected our voucher CPAP patients regardless of socioeconomic status. Moreover, all patients used the same masks and CPAP devices that are used in our public sleep clinic.

There were no significant differences in CPAP therapy success between the three private clinics. This may be due to our strict voucher regulations imposed on these private clinics regarding selection of medical staff, indication of the material used, requirements for reported results, and likely high motivation of these patients as they bypassed the public CPAP therapy waiting list. We previously showed that high willingness score in patients predicts CPAP therapy success at 1 year [8].

We observed that women abandoned CPAP therapy significantly more often than men in this study. Despite being more obese and older, the women in this study had sleep apnea that was slightly less severe than in men. There are several sleep apnea phenotypes and patient gender may affect symptom manifestation of sleep apnea. Bonsignore et al. reported that women appear to have more symptoms with lower AHI scores compared with men [12].

We previously observed that older sleep apnea patients had the same CPAP adherence as younger patients [8]. Although women abandoned CPAP statistically significantly more often than men, the proportions of patients who abandoned CPAP were relatively low.

One of the few studies describing the success of CPAP initiation in private clinics was reported by Lee et al. [13]. The success rate was 53% in this study and their clinic was sponsored. Our success rate was greater this previous study. As our CPAP initiation was performed using a voucher, it is possible that CPAP success could be different if a voucher was not used.

Our study has some limitations. Our conclusion applies to the specific national healthcare insurance system of Finland; therefore, it may not be possible to generalize our results to other healthcare insurance systems. The number of patients was not equal among clinics, but this also reflects the size of each clinic and how it attracts patients.

This study has some strengths. We describe one approach to alleviate the sleep apnea burden on public healthcare systems by engaging private clinics in sleep apnea therapy. The number of included patients is sufficient to draw conclusions. We believe that this study is the first to describe a collaboration between public and private healthcare to address the waiting list for sleep apnea treatment.