Introduction
Obstructive sleep apnea (OSA) is a prevalent and successively increasing multifaceted condition influencing the whole life situation of the patient [
1,
2]. Continuous positive airway pressure (CPAP) is the preferred treatment alternative [
3], especially for moderate and severe OSA, which if optimally used leads to reduced symptoms, improved metabolic control, lowered cardiovascular morbidity, as well as decreased all-cause and cardiovascular mortality [
4]. Despite these effects, patients often struggle during treatment initiation causing numerous early dropouts [
5,
6]. Long-term CPAP adherence, often defined as > 4 h use on 70% of the nights [
7] vary greatly [
8] and is generally seen as a substantial clinical problem [
9]. A dose-response relationship between CPAP usage and a variety of outcomes seem to exist, and the optimal adherence level differs depending on the outcome in question. Importantly, sleep duration should also be considered, and a usage level as high as possible is desirable [
6]. Two recent review studies [
10,
11] stated that socio-demographic characteristics (e.g., age, gender, socio economic status), symptoms and disease severity (e.g., daytime sleepiness and AHI), as well as treatment aspects (e.g., initiation procedure, side-effects), apart from symptomatic improvement, generally show limited predictive power for CPAP adherence. On the other hand, psychosocial variables (e.g., attitude, self-efficacy, illness and treatment beliefs or social support) have been found to be vital during the initiation in studies using patient- [
12‐
17], partner- [
18,
19] and practitioner-centred perspectives [
9,
20] and ought to be thought of as probable predictors for CPAP use [
6].
The initiation of CPAP is a complex procedure although it can be simplified and made more effective by a good interaction between patient and practitioner [
16,
20]. A recent survey including all CPAP centres in Sweden and Norway showed that practitioners perceived patients’ motivation, attitudes and knowledge to be the main determinants of CPAP adherence, but educating patients about effects, management and treatment adjustments were the most common actions they used to improve adherence [
9]. The value of basing CPAP treatment on theory and include psychosocial variables to understand the mechanisms of change and predictors of CPAP adherence has been stressed [
10]. A comprehensive and well-supported theory to understand human motivation is the Self-determination theory (SDT) [
21]. SDT posits that all behaviours lie along a continuum of relative autonomy, i.e., self-determination, mirroring the degree to which a person supports what he or she is doing. At one end of the self-determination continuum is behaviour that is intrinsically motivated and executed for its natural satisfaction, e.g., for the fun, curiosity or challenge it offers. At the other end is amotivation, which refers to a lack of intent to execute the behaviour. In between intrinsically motivated behaviours and amotivation lie behaviours that are described as extrinsic, suggesting that they are done to obtain certain outcomes contrary to intrinsic behaviours, which are done for their own sake. Four types of extrinsically motivated behaviours are recognized: integrated (i.e., behaviours consistent with a person’s values and needs, done because they signify what the person stands for), identified (i.e., behaviours experienced as beneficial to a person’s development, but not necessarily done with enjoyment), introjected (i.e., behaviours done to avoid negative feelings such as guilt or shame) and externally regulated (i.e., behaviours done to satisfy an external demand or reward contingency). Introjected and external regulations are portrayed as controlled motivation, whereas intrinsic, integrated and identified types of motivation are labelled autonomous motivation. A substantial body of research exists that shows that more autonomously motivated behaviours are more stable, performed with greater care and quality and accompanied by more positive experiences [
21]. Despite wide acknowledgment of the significance of motivation to use CPAP and adhere to the treatment, a validated questionnaire to measure and quantify motivation among patients with OSA is missing. By using a validated instrument when initiating CPAP, practitioners can identify patients with low motivation and after exploring causes subsequently improve adherence through dealing with identified reasons. The aim of this study was to develop a brief questionnaire to assess motivation to use CPAP that is psychometrically robust and suitable for use in clinical practice.
Discussion
Our study using psychometric testing under both CTT and Rasch measurement theory demonstrated robust psychometric properties for the newly developed MUC-S, the first validated tool to explore how a patient with OSA perceives motivation to use CPAP treatment. We found a stable and logical two-factor solution with nine items measuring autonomous and controlled motivation explaining 60% of the total variance. Another positive aspect was Cronbach’s alpha values of 0.88 and 0.86 which suggested good reliability for the two factors. Lack of differential item functioning of items across gender, excessive daytime sleepiness or insomnia groups revealed that patients with the same latent ability had equal probability of getting an item correct. The item score distribution showed a cumulative but consistent response pattern, with the majority of the patients scoring strongly agree or agree. This was seen particularly for items in factor one describing autonomous motivation, which might be explained by data being collected before CPAP treatment was initiated. Furthermore, in the latent class analyses [
36], we identified three subtypes of patients with high, medium and low motivation. Those with high motivation, the largest group (61%), had higher levels of daytime sleepiness, more problems from insomnia symptoms, a poorer global perceived health and a more positive attitude towards CPAP treatment which was deemed as logical based on data being collected before treatment initiation. However, this may change, particularly among patients experiencing side-effects [
38], wherefore the trajectory of motivation, as well as factors affecting motivation at different time points is of high importance to explore in future prospective studies.
CPAP is a multifaceted treatment for a chronic disorder, and the patient’s beliefs regarding suitability of the treatment should be considered as a factor of importance for adherence [
39]. Beliefs, either positive or negative, form the basis of a person’s attitude towards a phenomenon, e.g., how CPAP treatment affects health [
40] which in turn can be of importance for treatment motivation. In the Motivation to Engage in Treatment (MET) theory, six cognitive and emotional internal factors predict motivation to engage in treatment: problem recognition, level of suffering, external pressure, perceived cost of treatment, perceived suitability of treatment and outcome expectancy [
41]. External factors such as treatment, circumstances, situations, demographic factors and type of problems may influence the internal determinants. Understandably, clinical routines vary greatly [
9], and time during patient visits is often limited [
20], causing the communication focus to be more on practical aspects than behavioural aspects [
16], such as motivation [
12,
13], which may influence adherence to treatment negatively [
6,
14]. Unlike MET, and many social-cognitive theories, which illustrate different factors that predict motivation and behaviour change, the focus of SDT is on various types of motivation and how they influence behaviour. SDT states that the type of motivation (i.e., autonomous/self-determined or controlled/non-self-determined) is more vital than the amount of motivation [
21]. In a CPAP context, this means that the practitioner should strive to create a CPAP user driven by autonomous motivation. Such a patient is competent and driven by awareness of treatment benefits, in contrast to a patient who depends on controlled motivation and external regulation processes, for example, due to pressure conveyed by the CPAP practitioner. SDT incorporates a sub-theory, the Cognitive Evaluation Theory, which outlines factors that might hamper or enable different types of motivation and might form the basis of interventions to encourage more autonomous motivation. This theory suggests that more autonomous forms of motivation can be encouraged by feelings of competence, autonomy and a sense of relatedness [
21]. Metacognition (i.e., defined as the ability to recognize one’s own successful cognitive processing) is linked to these feelings, and of value when trying to improve CPAP adherence, but could be difficult to measure [
42]. Another aspect, important to note, is that OSA patients due to hypoxic processes might suffer cognitive impairments affecting short-term memory and concentration [
43]. In a CPAP context, especially when caring for an elderly patient with severe OSA, the clinician should therefore strive to adapt the communication situation [
16] to the patient’s cognitive ability [
44].
Few previous CPAP studies have used interventions primarily focused on motivation, but a few have shown promising results when focusing on this aspect. Positive results have been shown using motivational enhancement therapy [
12]. For example, in one study, the average nightly use of CPAP over 6 months was 99.0 min/night higher in the CPAP plus motivational enhancement therapy group, compared with the control group, an effect which was maintained over 12 months [
45]. Another alternative, motivational interviewing has also proven to increase adherence [
46]. Further, the relationship between the user and his/her partner might also positively influence motivation to use CPAP, since many patients tend to be “forced” into the CPAP clinic by their partner due to complaints of nightly disturbances or daytime symptoms such as fatigue and tiredness or fear of consequences [
18,
19]. Future CPAP studies should explore links between CPAP adherence, autonomous motivation and the need for competence and autonomy, as well as for relatedness.
The initiation of CPAP is a complex process carried out over time. Early (i.e., 1–4 weeks) and long-term follow-up visits (i.e., 3–6 months), depending on the patients’ needs, include education on lifestyle aspects, help with practical difficulties, as well as an evaluation of treatment adherence [
3]. Pathophysiology regarding OSA, technical aspects (i.e., function, care and maintenance of the device) as well as benefits and potential side-effects of CPAP, all areas adapted to the patients’ competences, should be covered [
9]. Practitioners should also as previously stated consider meeting a patient with cognitive impairment [
44]. Information delivered by a multidisciplinary team (e.g., the referring physician, a sleep specialist, as well as a sleep technician or CPAP nurse) is recommended [
16] with the intention to reach a shared treatment decision [
47]. Importantly, the increased understanding of health-behaviour change suggests the addition of specific care actions focusing behavioural change [
10], as well as use of brief scales measuring attitude, motivation, habit development and shared treatment decisions in clinical CPAP care to get an understanding of important aspects. Motivation might act as a mediator or moderator in between different variables.
Future prospective longitudinal studies should explore variables and/or scales within a wide range of patient-centred areas to get an understanding of aspects unique or with synergistic impact on motivation for CPAP use. Importantly, there is no single answer to solve the complex problem of motivation/nonadherence; many factors play a role. Considering the highlighted benefits of psychosocial variables [
10], the following instruments could be potential tools used together with MUC-S: ACTI [
15] (i.e., measuring attitude towards CPAP), CollaboRATE and SURE (i.e., measuring aspects of shared decision making) [
47] and the CPAP Habit Index-5 (i.e., measuring habit development) [
48]. Another interesting scale is the Self-Efficacy Measure for Sleep Apnea [
49] which explores a range of outcome expectations and aims to operationalize self-efficacy. Furthermore, it is of great importance to explore the correlation between objective CPAP use and MUC-S, and how motivation at different time-points can predict objective long-term use and healthcare utilization. The adoption of sophisticated statistical approaches (e.g., structural equational modelling) could be used to explore interactive effects of motivation between biomedical, other psychological as well as social variables on CPAP adherence.
Strengths and limitations
This is, to our knowledge, the first study that examines motivation to use CPAP treatment in patients with OSA. No other suitable instrument for measuring motivation in this context is available. A larger sample, with data being collected at different time points, might have led to a greater variation in the response pattern. According to general recommendations for 10 observations per item, the sample size was adequate for the validation analyses of the MUC-S with its 9 items [
35,
37]. A big strength of this study is the use of two important psychometric testing theories (CTT and Rasch models) [
27‐
31]. More specifically, CTT and Rasch models provide different advantages. With the two theories, healthcare practitioners can have better understanding in the psychometric features of the MUC-S and later benefit from using the MUC-S in assessing motivation to use CPAP treatment in patients with OSA.
There are some limitations in this study. First, all data were gathered before CPAP initiation, with patients who had agreed to come to the clinic and try CPAP, which might have affected their scores. No test-retest reliability was done. Therefore, whether the MUC-S score is stable over time is uncertain. Future prospective studies are warranted to examine the stability and reproducibility of the MUC-S including patients of both genders in various age groups and with a clinically relevant range of AHI (i.e., as seen at a CPAP clinic). Second, although the sample size is decent and sufficient for the current psychometric testing, our sample size was not large enough to conduct a cross-validation. More specifically, whether the factor structure found by our exploratory factor analysis can be verified in another sample is unknown. If we attempted to do a cross-validation, the current sample size should be at least twofold to fulfil the requirement in psychometric testing (i.e., a subsample tested using exploratory factor analysis like we did and another subsample using confirmatory factor analysis with a size of 200). Third, the convenience sampling used in this study restricts the generalizability of our findings, and future large-scale multicentre studies are therefore warranted. Whether MUC-S has promising psychometric properties in other ethnicity (e.g., Asians and African Americans) is also unsure.
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