Strengths and Limitations of the Study
To the best of our knowledge, this is the first study to combine the personalization of education and feedback based on personal therapy data with tailoring the style of the intervention to the psychological characteristics of the patient to promote CPAP adherence in a population with OSA.One of the core strengths of our study was that we worked closely with sleep clinics that invited patients, explained the study, onboarded the patients for the study, and guided the first assessments and delivery of the educational brochures. A motivated care professional who radiated the importance of the study may have had a positive impact on the adherence levels of the patients in the study.Another potential strength was that the weekly CPAP reports were delivered to the participants in the PT and PN groups through a physical mail service. The provision of physical reports may have attracted more attention from the participants and thereby led to a more in-depth processing of the materials. When considering the cost-effectiveness of the intervention and the increasing number of people who use digital means for communication, the delivery of materials in a digital manner is a likely alternative to physical mail. Because the intervention materials are already generated digitally and are fully automated, the delivery of the materials using digital channels would turn the intervention into a fully digital intervention with lower delivery costs. It remains to be seen whether the effects obtained in this study will persist when physical reports are replaced with digital reports. A recent meta-analytic review investigating the effectiveness of a broad range of eHealth interventions in improving CPAP treatment adherence showed that digital interventions hold promise as an alternative to more labor-intensive or otherwise costly interventions [A limitation of our study is that we did not include stratification by mask type in our randomization procedure. Studies seem to have shown that oronasal masks have been associated with lower therapy effectiveness and lower adherence levels than other types of masks [Another limitation of our study is that the design did not allow us to examine the impact of style tailoring in isolation. The provision of style tailoring in combination with personalized education and feedback was examined and compared with the provision of personalized education and feedback without style tailoring. A possible explanation for the failure to find an additional positive effect of style tailoring on adherence levels is that the personalized education and feedback intervention already increased adherence levels substantially, thereby limiting the room for further impact. Alternatively, there may have been short-lasting small effects that failed to impact our outcome measures. In the domain of health psychology, there is evidence suggesting that the impact of a health-related message can be enhanced when the style of the message is tailored to psychological characteristics that relate to how the receiver perceives and processes information [Another explanation could be that the psychological profiling framework (ie, the model of the 4 profiles, the assessment and allocation to 1 of the 4 profiles, and the corresponding templates for tailoring the style of the intervention materials) that we used was simply not effectively addressing the information processing needs of the existing patient population. Although the profiles were obtained from extensive qualitative research with patients and nurses and the tailoring strategies were validated with patients and nurses, we have no data to substantiate that these profiles sufficiently matched the information needs of the patients in this specific study.More and larger-scale research is needed to better understand the potential effects and specific implementation requirements that lead to a positive effect of style tailoring on adherence and adherence-related variables.