MATERIALS AND METHODS

RESULTS

Between August and December 2018, 1,501 subjects with OSA affiliated to the insurance company nationwide were interviewed. The interviewee, in 5% of the cases, was the main caregiver. Male participants were 53.6% of the sample and average age of all patients was 64.7 years (SD: 13.0 years).

Table 1 shows the characterization of the study population, with a predominance of subjects from the Bogotá Regional of the insurance company. More than half of the subjects were inactive workwise, and only 7% alternated between day and night shifts due to their occupation. The group of single, separated or widowed subjects accounted for a third of the total sample.

In terms of habits and healthy lifestyles, 58% of subjects slept accompanied and 52.2% performed at least 150 minutes of moderate aerobic physical activity per week. The recommended consumption of fruits and vegetables per day was barely seen in one third of the subjects, although the prevalence of tobacco consumption and alcohol risk consumption did not represent more than 5% each (Table 1).

In regards to the use of CPAP, almost a third of respondents were unaware of when the device was functioning properly. Symptoms such as difficulty sleeping due to the mask, nasal or throat discomfort and dry mouth represented the most frequent adverse events due to its use (Table 1). However, the satisfaction with the device reported by the subjects was good or very good in 82% of cases, regular (13%) and bad or very bad (5%).

The level of control of OSA, assessed by the absence of sleepiness referred by the subjects through the Epworth Scale, was observed in 41.7% of respondents. In respect to the associated comorbidity, 79% of subjects were overweight or obese at the time of the interview. Likewise, the first three conditions apart from overweight and obesity accompanying OSA were, in order of frequency, hypertension, upper respiratory tract conditions (recurrent rhinitis, sinusitis or laryngitis) and hypothyroidism (Table 1).

The evaluation of access to healthcare services revealed that 75% of subjects had a visit to the specialist for the management of their disease in the last six months, while 71% of them denied having been seen by respiratory therapy during the last year (Table 1). The level of satisfaction referred of the overall experience with the attention received for the management of OSA was good or very good in 75% of respondents, neutral (14%) and bad or very bad (11%).

In 670 (44.6%) subjects, information about the level of adherence was obtained by the registered reading of the electronic CPAP card. From these records, 57.9% of the sample population used the device for at least four hours in 70% or more of the previous 90 nights. While 79.5% of respondents reported, in the telephone interview, using CPAP for at least four hours, 5 days or more per week. The type of device most used was CPAP (82.7%), followed by Auto CPAP (8.6%), bilevel positive airway pressure (BPAP) (6.1%), and others (2.6%).

Table 2 provides the bivariable analysis resulting from the relationship between each of the factors studied and the adherence to the CPAP devices determined by the electronic record of the device. Age was the only demo-graphic factor significantly associated with adherence to CPAP, the proportion of subjects over 45 years was higher in the adherent groups. On the other hand, habits such as the consumption of fruits and vegetables, exercise and use of tobacco and alcohol were not associated with a greater or worse adherence to positive pressure devices.

Regarding the variables related to the CPAP, the device provider and the ability to operate the equipment were significantly associated with their adherence; meanwhile knowledge on how to adjust the mask to the face lingered at borderline of statistical significance (Table 2).

Three of the adverse events studied in relation to the use of CPAP devices showed a statistically significant association with the adherence to the device therapy. Thus, the proportion of subjects with difficulty sleeping due to the mask or nasal pad was higher in the non-adherent group, compared to the adherent group. Likewise, the non-adherent group referred ocular, chest and sinus discomforts or difficulty exhaling in higher frequency (Table 2).

None of the variables related to comorbidity showed a significant association with subjects' adherence to CPAP. However, in terms of access to services for the care of OSA, the specialized medicine visit in the last six months was a factor associated with adherence to the device. The proportion of subjects with a recent visit to the specialist was higher in the group of adherent subjects compared with non-adherent. The other variables of the care model studied were not associated with adherence to CPAP (Table 2).

The multivariable analysis of the data was based on a máximum model containing the variables of: age, sex, ability to operate the equipment, ability to adjust the mask/nasal pad to the face, difficulty sleeping due to the mask/nasal pad, ocular symptoms, abdominal distension, chest or paranasal sinuses discomforts or difficulty exha-ling, and specialized medicine consultation; considering as a level variable the CPAP service provider.

Only two of the factors of the maximum model were significantly related to subject's adherence to positive pressure devices, and two of them remained at border-line of statistical significance (Table 3). The ability to operate the equipment almost tripled the adherence odds (OR: 2.90; 95% CI: 1.32 to 6.38) compared to those who did not know how to operate it; while those that referred difficulty sleeping due to the mask/nasal pad reduced adhesion odds by 41%, compared to those that did not present this discomfort (Table 3).

On the other hand, being 45 years of age or older increased the odds of adherence to CPAP by 70%, compared with subjects 18 to 44 years of age, and presenting chest or sinus discomfort or difficulty exhaling decreased adhesion odds by 36%; although these effects were barely kept at borderline of statistical significance (Table 3).

The final model described was adjusted by the CPAP service provider as a level variable with a statistically significant residual intraclass correlation of 2.08% (95% CI 0.30 to 12.76). That is, the CPAP provider explains around 2% of the variability in the level of adherence.

DISCUSSION

Among the most relevant findings of this study, 58% of subjects with OSA used the CPAP device for at least 4 horas, 70% or more of the nights, reaching a control of daytime sleepiness of 41.7% of the sample analyzed. The factors associated with the adherence to these devices were the ability to operate the equipment and the difficulty sleeping due to the mask or nasal pad.

Likewise, the observed prevalence of overweight and obesity, arterial hypertension and diabetes mellitus concomitant with OSA itself as cardiovascular risk factors in the study population stand out. However, subjects referred low involvement in cardiovascular risk programs as well as education workshops for OSA management.

Similarly, the use of complementary forms of intervention to CPAP therapy, such as mandibular advancement devices were reported by less than 1% of the study population. However, the perceived satisfaction of the care received and the CPAP therapy itself was valued as good or very good primarily.

There are several reasons that can explain the level of adherence observed. Adverse events secondary to the use of the positive pressure devices affected a significant proportion of subjects in this study, which may not have been intervened successfully by the device provider during the subject's adaptation process. However, the level of adherence found is within the limits published by other authors in the literature, which range between 41.6% and 78%^8-10.

As in our work, authors such as Baratta et al.⁸ and Bazurto et al. ¹¹ have also assessed the main discomforts derived from the use of CPAP involved in discontinuation of therapy. These authors found that the complaints most frequently referred by subjects were upper airway symptoms (e.g. nasal) and those related to the facial mask (e.g. pressure). The latter closely linked to low adherence in our study. Unlike the findings of this work, several previously published studies have identified that cardiovascular risk factors, such as hypertension¹², history of myocardial infarction and cerebrovascular events8 and smoking ^8-9 constitute independent risk factors for poor adherence to CPAP.

In regards to the health value provided by CPAP therapy in subjects with OSA, the published results on the control of daytime sleepiness, measured using the Epworth Sleepiness Scale, show a frequency of symptomatic sleepiness of up to 58% of cases in subjects with different severity levels of the disease ^13-14. In our work, severe excessive daytime sleepiness affected 46% of adults with OSA, similar to that observed by Bostokeky et al. ¹³ after one to six months of treatment with CPAP in adults with severe disease.

The level of satisfaction with CPAP therapy has also been a subject of study in different publications. A survey of more than 3,000 users of these devices in France revealed that overall satisfaction was good or excellent in 90% of subjects ¹⁵. Likewise, in a clinical trial in Sweden in which two follow-up alternatives were compared in subjects with OSA, satisfaction with CPAP reached 99% in both groups ¹⁶. Although these values are higher than those observed in this study, the results of our work show a great consistency between the overall satisfaction with the CPAP and the one referred with the attention received for the management of OSA.

Although several of the adverse events secondary to the use of CPAP have been described in this study, other factors that determine adherence such as the knowledge of the risk derived from the disease and the perceptions and expectations regarding the therapy were not addressed by the interviews. Future analyzes of this nature, especially of a qualitative nature, could reveal other direct causes that explain poor adherence in certain groups of subjects.

In the Brostrõm et al. ¹⁷ study some of the barriers identified in CPAP users consisted of negative attitudes prior to and during the therapy, based on feelings of doubt regarding the certainty of the diagnosis and the need for CPAP therapy. Some subjects experienced shame at the need for treatment with CPAP and its use in the presence of other people.

The accessibility of information from the automatic readings of the electronic cards of the devices leads to the question of whether the subjects from which no information on the use of CPAP was obtained, the levels of adherence and their associated factors were the same as those found in the analyzed sample. However, in terms of the sample estimate made, the n studied was sufficient for the proposed objectives.

Considering the low involvement in cardiovascular programs in the study population, as well as the low participation of educational activities for the management of OSA, some questions are proposed that can be addressed by practice and research: Is the program offer, in health education and prevention aimed at patients with OSA, sufficient? Is the population with the disease aware of the value of treating their condition? Do patients with OSA know the risk of unwanted cardiovascular events or death? and finally, are the causes of non-compliance to available therapies by patients known and addressed by healthcare services?

It is well known how mandibular advancement devices an alternative to CPAP in subjects with mild and moderate OSA are, helping to prevent snoring and excessive daytime sleepiness ^18-19. Even these devices are as effective as CPAP in terms of the benefit on quality of life (sleepiness and functional and cognitive outcomes), according to a recent meta-analysis of randomized controlled clinical trials; effect attributed to a lower adherence of subjects to CPAP devices ²⁰.

Despite the above, in our study the use of mandibular advancement devices referred by subjects was very low, setting a favorable scenario for the inclusion of this technology to achieve cost-effective results in the population with OSA.

In conclusion, even with moderate adherence values and a good experience with CPAP therapy, the symptomatic control of the disease remains poor. The main factors associated with adherence were the subjects' ability to operate the equipment and the adverse effects due to the mask or nasal pad; both factors modifiable with a proper approach by the devices' service provider (e.g., reading the level of adherence, education about the use of CPAP or adjusting the face mask) ♣