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Adherence to Continuous Positive Airway Pressure therapy in Singaporean patients with Obstructive Sleep Apnea
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Adherence to Continuous Positive Airway Pressure therapy in Singaporean patients with Obstructive Sleep Apnea ⁎
Bernard Tan (Wen Sheng)a, , Alvin Tan (Kah Leong)a,b, Chan Yiong Huakc, Mok Yingjuand, Wong Hang Siangd, Hsu Pon Poha,b,e a
Department of Otolaryngology-Head and Neck Surgery, Changi General Hospital, Singapore Yong Loo Lin School of Medicine, National University of Singapore, Singapore c Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore d Department of Respiratory and Critical Care Medicine, Changi General Hospital, Singapore e Singapore University of Technology and Design, Singapore b
A R T I C LE I N FO
A B S T R A C T
Keywords: Obstructive Sleep Apnea OSA Continuous Positive Airway Pressure CPAP CPAP adherence CPAP compliance
Purpose: To investigate the rates of Continuous Positive Airway Pressure (CPAP) uptake and adherence amongst Singaporean patients diagnosed with Obstructive Sleep Apnea (OSA), and to evaluate factors correlated with CPAP uptake and adherence. Study design: Retrospective review of medical records. Methods: Medical records were reviewed for baseline demographics, daytime sleepiness, presence of nasal symptoms and OSA severity, initial treatment choice, the rate of CPAP treatment uptake and CPAP adherence at 1 and 12 months. Results: 2160 patients were diagnosed with OSA within the 5-year period (2011–2015). 463 (21.4%) had mild OSA, 583 (27.0%) had moderate OSA and 1114 (51.6%) had severe OSA. For initial therapy, 751 (34.8%) patients opted for a 1-month CPAP trial, 288 (13.3%) patients chose surgery upfront, 291 (13.5%) patients chose adjunctive treatments (weight loss, positional therapy, dental appliance, intranasal steroid spray for allergic rhinitis) and 830 (38.4%) patients rejected all forms of treatment. 337 out of 751 patients (44.9%) were adherent to CPAP therapy during the 1 month trial. 381 out of 751 (50.7%) patients took up CPAP therapy following the trial period, of which 299 out of 381 (78.5%) patients were adherent to CPAP therapy at 1 year. CPAP adherence during the 1-month trial was a predictor for eventual CPAP treatment uptake and CPAP adherence at 1 year (p < 0.001). Age (p < 0.001), BMI (p < 0.001) and normal ESS (p = 0.01) were predictors of treatment rejection. 24 patients underwent upper airway surgery during their first year of using CPAP. 21 out of the 24 patients (87.5%) were adherent to CPAP at 1 year after undergoing surgery. These patients had a higher rate of CPAP adherence compared to the overall cohort (87.5% versus 78.5%), but this was not statistically significant (p > 0.05). Conclusion: Singaporean patients who accept CPAP therapy after an initial 1-month CPAP trial will generally be adherent to CPAP therapy. Initial patterns of CPAP usage are predictive of long term CPAP adherence. However, there is a high rate of CPAP treatment rejection both at the time of diagnosis and after the CPAP trial. Upper airway surgery in selected patients may improve CPAP adherence.
1. Introduction Obstructive Sleep Apnea (OSA) is a disorder that is characterized by obstructive apneas and hypopneas/respiratory effort related arousals caused by repetitive complete or partial collapse of the upper airway during sleep. Left untreated, OSA is associated with impaired daytime
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performance, an increased risk of traffic accidents, hypertension, neuropsychological disturbances, cardiovascular events and all cause mortality. It is a chronic disease which requires long term multidisciplinary care [1]. Continuous Positive Airway Pressure (CPAP) is the first line treatment for OSA. The CPAP machine generates a positive pharyngeal
Corresponding author. E-mail address: [email protected] (B. Tan).
https://doi.org/10.1016/j.amjoto.2018.05.012 Received 17 April 2018 0196-0709/ © 2018 Elsevier Inc. All rights reserved.
Please cite this article as: Sheng, B.T.W., Am J Otolaryngol (2018), https://doi.org/10.1016/j.amjoto.2018.05.012
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Table 1 Studies on CPAP uptake and adherence in Asian populations. Source/year
Country
Follow up period
Disease severity
Cohort size
CPAP acceptance
CPAP adherence (patients who accepted CPAP)
Author's own data Lee et al./2017 [3]
Singapore Singapore
1 year 1 year
751 135
50.7% 57.8%
78.5% 52.6%
Hussain et al./2014 [4] Yang et al./2013 [5] Tokunaga et al./2013 [6] Tanahashi et al./2012 [7] Wang et al./2012 [8] Hui et al./2001 [9]
Pakistan Taiwan Japan Japan China Hong Kong
1 year 9 months 2 years 6 months 30 months 3 months
Mild, moderate and severe OSA Moderate OSA with ESS > 10 and severe OSA Mild, moderate and severe OSA Mild, moderate and severe OSA Moderate and severe OSA Mild, moderate and severe OSA Severe OSA Moderate and severe OSA
75 315 204 101 210 112
80% 40% – 87% 66.8% –
76.7% 64% 89.8% 38% 64.3% 72%
At the Integrated Sleep Service of Changi General Hospital, patients with sleep disorders receive multidisciplinary care - comprising of medical professionals and allied health personnel from the medical specialties: Otolaryngology, Respiratory Medicine, Neurology, Psychiatry, Oromaxillofacial Surgery, Bariatric Surgery, Sports Medicine and Endocrinology. After their diagnostic sleep study is performed, patients are reviewed by a sleep specialist. Their diagnosis of OSA is explained and treatment recommendations are made. CPAP or adjunctive therapy (positional, oral appliance, treatment of allergic rhinitis and weight loss) is encouraged. Surgical treatment is not advocated as an initial treatment, and is only pursued if the patient declines nonsurgical therapies and has a clear anatomical site of airway obstruction that interferes with CPAP usage. The treatment plan is tailored to the individual, and relevant referrals are made within the Integrated Sleep Service based on the needs of the patient (e.g. - referral to a Sports physician, physiotherapist, dietician and Endocrinologist for the management of morbid obesity and enrolment in a structured weight loss programme, or referral to the oromaxillofacial surgeon for creation of mandibular advancement device). For the purposes of data collection, patients are classified into 4 groups based on their choice of initial treatment - CPAP, surgery, adjunctive treatments and rejection of treatment. Patients were counted into the CPAP treatment group if they accepted a 1-month CPAP trial as their initial treatment, with the possibility of long term CPAP therapy thereafter. Most of these patients also received adjunctive treatment (such as enrolment in a weight loss programme and treatment of their allergic rhinitis) and several of them underwent surgery while on CPAP, but as CPAP was their primary treatment they were assigned to the CPAP group. Patients who opted for surgery as an initial treatment were classified into the surgery group. Many of these patients also received adjunctive treatments, but none were using CPAP. Patients who were grouped as receiving adjunctive treatments (positional therapy, oral appliance, treatment of allergic rhinitis and weight loss) did not use CPAP or undergo surgery. Lastly, patients were considered to have rejected therapy if they attended their initial consultation and declined all treatment for OSA (accepting the risks of untreated OSA), or if they did not attend the consultation after completing their sleep study. The diagnosis of OSA is established when a patient undergoing a diagnostic sleep study has an AHI of 5 or more. Patients were classified by AHI into mild (AHI ≥5 and < 15), moderate (≥15 and < 30) and
transmural pressure so that the intraluminal pressure exceeds the surrounding pressure. As a result, respiratory events due to upper airway collapse are prevented [1]. While CPAP is highly effective when used, non-adherence to therapy is a major issue. A patient with OSA needs to use CPAP for at least 4 h a night to experience reduction in daytime somnolence and neurocognitive function, and reduce risk of developing cardiovascular and metabolic comorbidities. Hence, > 4 h of CPAP use per night on most nights (> 70% of nights) is used as the definition of CPAP adherence/CPAP compliance by many authors [1]. CPAP adherence rates are variable, with previous studies (using data from Western countries) showing 17–54% of patients being adherent to CPAP [2]. CPAP adherence rates in Asian populations report a 38–90% adherence rate [3–9] (Table 1); recent Western data reports a comparable 37.3–87.5% adherence rate (Table 2) Only one study to date has evaluated the CPAP adherence in Singaporean patients [3]. Factors which are associated with CPAP adherence and non-adherence has been a topic of extensive research. Factors influencing CPAP adherence include: disease and patient characteristics, treatment titration procedures, device factors, psychological and social factors. Barriers to CPAP acceptance include: cost, inconvenience, discomfort, do not see the need for treatment and choice of alternative therapies [1–3]. 2. Methods The aim of the study was to investigate the rates of Continuous Positive Airway Pressure (CPAP) uptake and adherence amongst Singaporean patients diagnosed with Obstructive Sleep Apnea (OSA), and to evaluate factors correlated with CPAP uptake and adherence. The study involved the retrospective review of medical records of patients of the Integrated Sleep Service of Changi General Hospital (a tertiary referral hospital). These patients underwent a diagnostic sleep study between January 2011 to December 2015 and were diagnosed with OSA. Their medical records were accessed the following information was obtained-age, gender, Body Mass Index (BMI), Epworth Sleepiness Score (ESS), presence of nasal symptoms, Apnea-Hypopnea Index (AHI), choice of initial treatment for OSA (CPAP, surgery, adjunctive therapies, reject treatment), CPAP uptake, CPAP adherence at 1 and 12mths. Table 2 Studies on CPAP acceptance and adherence in Western populations. Source/year
Country
Follow up period
Disease severity
Cohort size
CPAP acceptance
CPAP adherence
Jacobsen et al./2017 [10] Lanza et al./2017 [11] Budhiraja et al./2017 [12] McMillan et al./2014 [13] Ching et al./2013 [14] Nadal et al./2017 [15]
Denmark Italy USA UK Australia/New Zealand Spain
3 years 1 year 6 months 1 year 1 year 6 months
All OSA Severe OSA Severe OSA Severe OSA Moderate and severe OSA Moderate and severe OSA
695 144 394 102 50 191
– – – – – –
78% 87.5% 67.3% 35.3% 46% 75%
2
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severe (AHI ≥30) OSA. CPAP adherence was defined as 4 h/night use, 70% of nights, based on machine report. Patients who did not have a CPAP machine report were considered to be non-adherent, even if they claimed to use their CPAP for > 4 h per day. CPAP uptake is defined as acceptance of CPAP therapy after the initial trial period and obtaining a personal CPAP machine. Patients who had diagnoses other than OSA, such as insomnia, parasomnia, central sleep apnea, mixed sleep apnea, narcolepsy, restless leg syndrome, periodic limb movement disorder and obesity hypoventilation syndrome were excluded from the study. The small number of patients who were issued BIPAP (instead of CPAP) were excluded from the study. All patients underwent in-laboratory level 1 diagnostic sleep studies (Compumedics PS, Melbourne, Australia) which included continuous electroencephalogram, oculogram, electrocardiogram, electromyogram, nasal airflow, thoracic and abdominal respiratory movements, pulse oximetry, snore volume, position and video monitoring. All studies were scored by a Registered Polysomnographic Technologist (RPSGT), certified by the Board of Registered Polysomnographic Technologists in the United States. The American Academy of Sleep Medicine (AASM) 2007 criteria was used. All patients who were prescribed CPAP underwent CPAP counselling prior to a CPAP trial to educate them on the rationale, benefits, common side effects and common technical issues encountered with CPAP. Patients were fitted with an appropriate mask interface (> 95% of patients used a nasal mask). CPAP treatment was initiated with auto-PAP in all cases. Patients were loaned a CPAP machine for a free 1-month trial. A RPSGT would call the patient over the phone 1 week into the trial to check on the patients and assist with any issues affecting CPAP adherence. At the end of the trial, patients who accepted long term CPAP therapy (“CPAP uptake”) would purchase a CPAP machine (via the hospital or through their own channels). Analyses were performed using SPSS 24.0 with statistical significance set at p < 0.05. Logistic regression analysis was performed to evaluate the variables associated with treatment rejection, CPAP uptake after 1-month trial and CPAP adherence at 1 year with odds ratios & 95% CI reported.
Table 3 Characteristics of overall study population (n = 2160). Factor
Results
Gender Age BMI Obese (BMI > 27) ESS
1773 (82.1%) were male and 387 (17.9%) were female 44.7 (range 14–89) 30.0 (range 15–75) 1378 (63.8%) obese Mean 18.6 (range 0–24) 787 (36.4%) had ESS > 10 820 (38.0%) 463 (21.4%) had mild OSA, 583 (27.0%) had moderate OSA and 1114 (51.6%) had severe OSA CPAP trial - 751 (34.8%) Surgery - 288 (13.3%) Adjunctive treatments - 291 (13.5%) Rejected treatment - 830 (38.4%)
Nasal symptoms OSA severity Initial therapy
Note: Adjunctive treatments refer to treatments for OSA other than CPAP or surgery. These are: positional therapy, oral appliance, treatment of allergic rhinitis with intranasal corticosteroids and weight loss.
(p < 0.001). Age, gender, BMI, ESS, presence of nasal symptoms and AHI were not predictive of CPAP uptake after CPAP trial (Table 4 and Fig. 1). 3.3. CPAP adherence at 1 year Following CPAP uptake, 299 out of 381 (78.5%) patients were adherent to CPAP therapy at 1 year. Univariate and multivariate analysis of age, gender, BMI, ESS, presence of nasal symptoms, AHI did not reveal any of these factors to be predictive of CPAP uptake after CPAP trial. CPAP adherence at 1 month was a predictor of CPAP adherence at 1 year (p < 0.001) (Table 4 and Fig. 1). 3.4. Surgery while on CPAP 24 patients underwent surgery during their first year of using CPAP. 11 patients underwent nasal surgery, 10 underwent palatal surgery and 3 underwent combined nasal and palatal surgery. 21 out of the 24 patients (87.5%) were adherent to CPAP at 1 year after undergoing surgery during their first year of CPAP. Univariate analysis did not show surgery during the first year of CPAP use to be predictive of CPAP adherence at 1 year (p > 0.05).
3. Results 3.1. Overall cohort 2160 patients were diagnosed with OSA within the 5-year period. 1773 (82.1%) were male and 387 (17.9%) were female. Mean age was 44.7 years old (range 14–89). Mean BMI was 30.0 (range 15–75). 1378 (63.8%) were obese with BMI > 27. Mean ESS was 18.6 (range 0–24), 787 (36.4%) had ESS > 10. 820 (38.0%) of patients had significant nasal symptoms. 463 (21.4%) had mild OSA, 583 (27.0%) had moderate OSA and 1114 (51.6%) had severe OSA. For initial therapy, 751 (34.8%) patients opted for 1-month long CPAP trial, 288 (13.3%) patients chose surgery, 291 (13.5%) patients chose adjunctive treatments (dental appliance, weight loss, positional therapy, treatment of allergic rhinitis) and 830 (38.4%) patients rejected all forms of treatment (Table 3).
3.5. Treatment rejection Univariate and multivariate analysis showed that older age, higher BMI and normal ESS were correlated with treatment rejection. Age was a predictor, with older patients more likely to reject treatment (p < 0.001). Patients with higher BMI were more likely to reject treatment (p = 0.013). Patients with normal ESS (≤10) were more likely to reject treatment (p = 0.01). Gender, presence of nasal symptoms and AHI were not predictive of treatment rejection (Table 4). 4. Discussion
3.2. CPAP trial and uptake 4.1. CPAP adherence and uptake Out of the 751 patients who underwent the 1-month long CPAP trial, 337 (44.9%) were adherent to CPAP therapy. 381 out of 751 (50.7%) patients took up CPAP therapy by obtaining a personal CPAP unit following the trial period. Out of the 381 patients who took up CPAP, 254 (66.7%) were adherent to CPAP therapy and 127 (33.3%) were not adherent to CPAP therapy during the 1-month trial. Amongst the 370 who completed the CPAP trial but did not take up CPAP, 83 (22.4%) had been adherent to CPAP therapy and 287 (77.6%) were not adherent to CPAP therapy. Univariate and multivariate analysis showed CPAP adherence at 1 month was a predictor of CPAP uptake after trial
78.5% (299 out of 381) of our patients who accepted CPAP therapy were adherent to CPAP at 1 year, making it one of the highest rates of adherence in international literature [1–9]. A possible reason for the high adherence rate is the high cost of CPAP which has to be paid out of pocket may select for patients who are highly motivated to undergo treatment. In addition, the practice of allowing patients a free 1-month CPAP trial period (patients only have to purchase a personal CPAP mask) allows the patients to have sufficient time to experience CPAP therapy prior to making their decision whether to accept or decline 3
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Table 4 CPAP trial, uptake and adherence. Outcome
Result
CPAP 1-month trial CPAP adherence at 1 month
751 patients 337 out of 751 patients (44.9%) were regular users 381 out of 751 patients (50.7%) 254 patients (66.7%) were regular users 127 patients (33.3%) were not regular users 370 out of 751 patients (49.3%) 83 patients (22.4%) were regular users 287 patients (77.6%) were not regular users 299 out of 381 (78.5%) were regular users
CPAP uptake after trial
CPAP non-uptake after trial
CPAP adherence at 1 year
Factors associated with outcomes
Results
Univariate and multivariate analysis of age, gender, BMI, ESS, presence of nasal symptoms, AHI CPAP adherence at 1 mth Univariate and multivariate analysis of age, gender, BMI, ESS, presence of nasal symptoms, AHI CPAP adherence at 1 mth
Not predictive of CPAP uptake (p > 0.05) Predictive of CPAP uptake (p < 0.001) Not predictive of CPAP adherence at 1 year (p > 0.05) Predictive of CPAP adherence at 1 year (< p < 0.001)
Patients with OSA (n= 2160)
CPAP 1 month trial 751 patients (34.8%)
Surgery 288 patients (13.3%)
Adjunctive treatments 291 patients (13.5%)
Rejected all treatments 830 patients (38.4%)
Adherent to CPAP (1 month) 337 patients (44.9%)
CPAP non uptake 370 patients (49.3%)
Non-adherent to CPAP (1 year) 82 patients (21.5%)
CPAP uptake 381 patients (50.7%)
Adherent to CPAP (1 year) 299 patients (78.5%)
Fig. 1. Choice of initial treatment in patients with OSA, CPAP trial, uptake, adherence at 1 month and 1 year in a cohort of Singaporean patients with OSA.
also unable to utilize their Medisave funds (mandatory national healthcare savings scheme) and few local insurance companies cover the cost of a CPAP machine. Hence, patients are willing to undergo a diagnostic sleep study but many decline CPAP therapy due to the costs involved. Authors from other Asian privately funded healthcare systems report facing similar issues [5,8]. Other reasons why patients declined CPAP therapy after CPAP trial include: inconvenience of treatment, poor disease perception (did not understand the need for treatment) or decision to switch to another treatment for OSA [3].
CPAP therapy, thereby selecting for patients who are able to tolerate CPAP. However, our patient cohort had a low CPAP uptake rate after CPAP trial of 50.7% (381 out of 751). Out of the entire patient cohort, only 17.6% (381 out of 2160) accepted CPAP therapy, of which only 13.8% (299 out of 2160) were adherent to CPAP therapy. Several factors could possibly account for this. The high cost of CPAP acts as a barrier to uptake of CPAP therapy after the diagnosis of OSA. In the Singaporean healthcare system, the diagnosis of OSA (medical consultations and inpatient diagnostic sleep studies) is funded by public funds or insurers, while CPAP therapy is not. On the other hand, most patients are required to purchase CPAP machines with cash. The cost of a CPAP machine averages SGD$1500–S$2000 (USD$1100–1500), which is about half of the median monthly salary of SGD $4232 (2017 data). Government subsidies are only available to the very needy. Patients are
4.2. Treatment rejection and untreated disease burden Our patients had a high upfront treatment rejection rate of 38.4% (830 out of 2160), who declined all OSA therapy at the initial consultation after the diagnostic sleep study or did not even turn up. The 4
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actual treatment rejection rate is likely to be higher - the majority of patients who underwent a CPAP trial but did not accept CPAP therapy ended up rejecting all treatments. The patients who opted for alternative treatments (including weight loss, oral appliances, treatment of allergic rhinitis, positional therapy) may or may not have been adherent to their chosen treatment, and their chosen treatment may or may not have been effectively treating their OSA. In the group of patients who opted for surgery, most declined a postoperative sleep study due to the time and cost involved, or if their symptoms had resolved. Thus, the burden of untreated disease is significant. Analysis of our data showed that older patients, patients with higher BMI and patients with normal ESS were more likely to reject treatment for OSA. Awareness of patients at risk of rejecting treatment can allow healthcare providers to focus their efforts on these patients to increase awareness of disease.
but this was not statistically significant, possibly due to small sample size and high overall rate of CPAP adherence.
4.3. Predictors of CPAP adherence
4.7. Strengths of the study
In our study - adherence to CPAP at 1 month is predictive of CPAP uptake as well as CPAP adherence at 1 year. This corroborates multiple studies which have shown that early patterns of CPAP usage are predictive of long term usage [2,16]. However, from our data-age, gender, BMI, ESS, presence of nasal symptoms and AHI were not predictive of CPAP uptake or CPAP adherence at 1 year. In several other studies, disease severity as measured by AHI and ESS has been shown to be correlated to CPAP adherence, with patients with higher AHI and ESS more likely to use CPAP. Age, gender and BMI are inconsistently correlated with CPAP adherence [1,3,17–19]. Objective measures of nasal resistance have been correlated with lower rates of CPAP uptake and adherence [20–21]. The lack of correlation between these factors and the outcome of CPAP uptake and adherence in our study does not show that they are not associated, but rather reflects that multiple factors can interact and influence a patient's decision to accept and adhere to CPAP.
Our study has the distinction of having the largest patient cohort size amongst studies conducted in Asian populations [3–9]. In addition, our assessment of CPAP adherence relies on CPAP machine data, as selfreported CPAP usage has been shown to be inaccurate and over-estimates actual CPAP use [16–19].
4.4. Improving CPAP adherence
5. Conclusion
Several steps have been taken improve the CPAP adherence amongst our patients at the Integrated Sleep Service of Changi General Hospital. Increased patient and spousal education efforts take place through detailed CPAP education sessions and written information handouts prior to CPAP initiation. Patients who have tried CPAP at home and are facing issues are offered the option of a 1-night CPAP titration study in the sleep laboratory to allow for onsite support and troubleshooting. Patients can also be referred for Cognitive Behavioural Therapy by a trained psychologist to help them to overcome psychological and social barriers to CPAP therapy. Patients using CPAP with severe nasal obstruction not responding to medical therapy are offered nasal surgery by the ENT surgeon [1,21].
Singaporean patients who accept CPAP therapy after an initial 1month CPAP trial will generally be adherent to CPAP therapy (78.5%, 299 out of 381). Initial patterns of CPAP usage (adherence at 1 month) is predictive of long term (1 year) CPAP adherence (p < 0.001). However, only a small proportion of the entire patient cohort accepted CPAP therapy (17.6%, 381 out of 2160), of which only 13.8% (299 out of 2160) were adherent to CPAP therapy at 1 year. Upper airway surgery in selected patients may improve CPAP adherence.
4.5. Surgery
Conflict of interest
A significant proportion of patients (13.5%, 291 out of 2160) opted for surgical treatment as an initial treatment, despite a trial of CPAP and other non-surgical treatments being advocated. Possible reasons for patients opting for surgery as an initial treatment include: availability of funding (from government subsidies, insurance coverage and Medisave), desire for a swift solution and aversion to be dependent on a long-term therapy. Multiple studies have found that upper airway surgery in select patients can improve CPAP adherence [22–24]. In our study, a small number of patients who completed a CPAP trial and proceeded to uptake CPAP therapy also underwent surgery during the first year of using CPAP (24 out of 381 patients, 6.3%). For these patients, the goal of surgery was to facilitate CPAP delivery and adherence by addressing anatomical sites of obstruction. These patients had a higher rate of CPAP adherence compared to the overall cohort (87.5% versus 78.5%),
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
4.6. Patients with mild OSA Patients with mild OSA do not necessarily require CPAP and we advocate other treatments such as surgery, dental appliances, weight loss and positional therapy to this group. However, some patients do request for CPAP due to personal preference and we allow them to experience a trial of CPAP therapy. In our cohort, 49 out of the 463 (10.6%) patients diagnosed with mild OSA opted for CPAP as an initial therapy. After the 1-month CPAP trial, 23 out of the 49 took up long term CPAP therapy, and 19 out of 23 patients were adherent to CPAP at 1 year.
4.8. Limitations of the study Our study has several limitations. Firstly, the follow up duration of 1 year is a relatively short time period, given that OSA is a chronic disease. It is possible that given a longer follow up period, the CPAP adherence rate would have reduced. Secondly, only the patient's initial choice of treatment is recorded and crossing over of patients between the various treatment options is not reflected. Thirdly, there was limited evaluation of the numerous known predictors of CPAP adherence in view of the study's retrospective design.
Funding No funding was received for this research.
Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/ or national research committee (name of institute/committee) and with the 1964 Helsinki declaration and its later amendments or comparable 5
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ethical standards. For this type of study formal consent is not required. Singhealth Combined Institutional Review Board (CIRB) ethical approval was sought and obtained (Reference: 2017/2819) prior to commencement of the study.
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Am J Otolaryngol journal homepage: www.elsevier.com/locate/amjoto
Adherence to Continuous Positive Airway Pressure therapy in Singaporean patients with Obstructive Sleep Apnea ⁎
Bernard Tan (Wen Sheng)a, , Alvin Tan (Kah Leong)a,b, Chan Yiong Huakc, Mok Yingjuand, Wong Hang Siangd, Hsu Pon Poha,b,e a
Department of Otolaryngology-Head and Neck Surgery, Changi General Hospital, Singapore Yong Loo Lin School of Medicine, National University of Singapore, Singapore c Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore d Department of Respiratory and Critical Care Medicine, Changi General Hospital, Singapore e Singapore University of Technology and Design, Singapore b
A R T I C LE I N FO
A B S T R A C T
Keywords: Obstructive Sleep Apnea OSA Continuous Positive Airway Pressure CPAP CPAP adherence CPAP compliance
Purpose: To investigate the rates of Continuous Positive Airway Pressure (CPAP) uptake and adherence amongst Singaporean patients diagnosed with Obstructive Sleep Apnea (OSA), and to evaluate factors correlated with CPAP uptake and adherence. Study design: Retrospective review of medical records. Methods: Medical records were reviewed for baseline demographics, daytime sleepiness, presence of nasal symptoms and OSA severity, initial treatment choice, the rate of CPAP treatment uptake and CPAP adherence at 1 and 12 months. Results: 2160 patients were diagnosed with OSA within the 5-year period (2011–2015). 463 (21.4%) had mild OSA, 583 (27.0%) had moderate OSA and 1114 (51.6%) had severe OSA. For initial therapy, 751 (34.8%) patients opted for a 1-month CPAP trial, 288 (13.3%) patients chose surgery upfront, 291 (13.5%) patients chose adjunctive treatments (weight loss, positional therapy, dental appliance, intranasal steroid spray for allergic rhinitis) and 830 (38.4%) patients rejected all forms of treatment. 337 out of 751 patients (44.9%) were adherent to CPAP therapy during the 1 month trial. 381 out of 751 (50.7%) patients took up CPAP therapy following the trial period, of which 299 out of 381 (78.5%) patients were adherent to CPAP therapy at 1 year. CPAP adherence during the 1-month trial was a predictor for eventual CPAP treatment uptake and CPAP adherence at 1 year (p < 0.001). Age (p < 0.001), BMI (p < 0.001) and normal ESS (p = 0.01) were predictors of treatment rejection. 24 patients underwent upper airway surgery during their first year of using CPAP. 21 out of the 24 patients (87.5%) were adherent to CPAP at 1 year after undergoing surgery. These patients had a higher rate of CPAP adherence compared to the overall cohort (87.5% versus 78.5%), but this was not statistically significant (p > 0.05). Conclusion: Singaporean patients who accept CPAP therapy after an initial 1-month CPAP trial will generally be adherent to CPAP therapy. Initial patterns of CPAP usage are predictive of long term CPAP adherence. However, there is a high rate of CPAP treatment rejection both at the time of diagnosis and after the CPAP trial. Upper airway surgery in selected patients may improve CPAP adherence.
1. Introduction Obstructive Sleep Apnea (OSA) is a disorder that is characterized by obstructive apneas and hypopneas/respiratory effort related arousals caused by repetitive complete or partial collapse of the upper airway during sleep. Left untreated, OSA is associated with impaired daytime
⁎
performance, an increased risk of traffic accidents, hypertension, neuropsychological disturbances, cardiovascular events and all cause mortality. It is a chronic disease which requires long term multidisciplinary care [1]. Continuous Positive Airway Pressure (CPAP) is the first line treatment for OSA. The CPAP machine generates a positive pharyngeal
Corresponding author. E-mail address: [email protected] (B. Tan).
https://doi.org/10.1016/j.amjoto.2018.05.012 Received 17 April 2018 0196-0709/ © 2018 Elsevier Inc. All rights reserved.
Please cite this article as: Sheng, B.T.W., Am J Otolaryngol (2018), https://doi.org/10.1016/j.amjoto.2018.05.012
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Table 1 Studies on CPAP uptake and adherence in Asian populations. Source/year
Country
Follow up period
Disease severity
Cohort size
CPAP acceptance
CPAP adherence (patients who accepted CPAP)
Author's own data Lee et al./2017 [3]
Singapore Singapore
1 year 1 year
751 135
50.7% 57.8%
78.5% 52.6%
Hussain et al./2014 [4] Yang et al./2013 [5] Tokunaga et al./2013 [6] Tanahashi et al./2012 [7] Wang et al./2012 [8] Hui et al./2001 [9]
Pakistan Taiwan Japan Japan China Hong Kong
1 year 9 months 2 years 6 months 30 months 3 months
Mild, moderate and severe OSA Moderate OSA with ESS > 10 and severe OSA Mild, moderate and severe OSA Mild, moderate and severe OSA Moderate and severe OSA Mild, moderate and severe OSA Severe OSA Moderate and severe OSA
75 315 204 101 210 112
80% 40% – 87% 66.8% –
76.7% 64% 89.8% 38% 64.3% 72%
At the Integrated Sleep Service of Changi General Hospital, patients with sleep disorders receive multidisciplinary care - comprising of medical professionals and allied health personnel from the medical specialties: Otolaryngology, Respiratory Medicine, Neurology, Psychiatry, Oromaxillofacial Surgery, Bariatric Surgery, Sports Medicine and Endocrinology. After their diagnostic sleep study is performed, patients are reviewed by a sleep specialist. Their diagnosis of OSA is explained and treatment recommendations are made. CPAP or adjunctive therapy (positional, oral appliance, treatment of allergic rhinitis and weight loss) is encouraged. Surgical treatment is not advocated as an initial treatment, and is only pursued if the patient declines nonsurgical therapies and has a clear anatomical site of airway obstruction that interferes with CPAP usage. The treatment plan is tailored to the individual, and relevant referrals are made within the Integrated Sleep Service based on the needs of the patient (e.g. - referral to a Sports physician, physiotherapist, dietician and Endocrinologist for the management of morbid obesity and enrolment in a structured weight loss programme, or referral to the oromaxillofacial surgeon for creation of mandibular advancement device). For the purposes of data collection, patients are classified into 4 groups based on their choice of initial treatment - CPAP, surgery, adjunctive treatments and rejection of treatment. Patients were counted into the CPAP treatment group if they accepted a 1-month CPAP trial as their initial treatment, with the possibility of long term CPAP therapy thereafter. Most of these patients also received adjunctive treatment (such as enrolment in a weight loss programme and treatment of their allergic rhinitis) and several of them underwent surgery while on CPAP, but as CPAP was their primary treatment they were assigned to the CPAP group. Patients who opted for surgery as an initial treatment were classified into the surgery group. Many of these patients also received adjunctive treatments, but none were using CPAP. Patients who were grouped as receiving adjunctive treatments (positional therapy, oral appliance, treatment of allergic rhinitis and weight loss) did not use CPAP or undergo surgery. Lastly, patients were considered to have rejected therapy if they attended their initial consultation and declined all treatment for OSA (accepting the risks of untreated OSA), or if they did not attend the consultation after completing their sleep study. The diagnosis of OSA is established when a patient undergoing a diagnostic sleep study has an AHI of 5 or more. Patients were classified by AHI into mild (AHI ≥5 and < 15), moderate (≥15 and < 30) and
transmural pressure so that the intraluminal pressure exceeds the surrounding pressure. As a result, respiratory events due to upper airway collapse are prevented [1]. While CPAP is highly effective when used, non-adherence to therapy is a major issue. A patient with OSA needs to use CPAP for at least 4 h a night to experience reduction in daytime somnolence and neurocognitive function, and reduce risk of developing cardiovascular and metabolic comorbidities. Hence, > 4 h of CPAP use per night on most nights (> 70% of nights) is used as the definition of CPAP adherence/CPAP compliance by many authors [1]. CPAP adherence rates are variable, with previous studies (using data from Western countries) showing 17–54% of patients being adherent to CPAP [2]. CPAP adherence rates in Asian populations report a 38–90% adherence rate [3–9] (Table 1); recent Western data reports a comparable 37.3–87.5% adherence rate (Table 2) Only one study to date has evaluated the CPAP adherence in Singaporean patients [3]. Factors which are associated with CPAP adherence and non-adherence has been a topic of extensive research. Factors influencing CPAP adherence include: disease and patient characteristics, treatment titration procedures, device factors, psychological and social factors. Barriers to CPAP acceptance include: cost, inconvenience, discomfort, do not see the need for treatment and choice of alternative therapies [1–3]. 2. Methods The aim of the study was to investigate the rates of Continuous Positive Airway Pressure (CPAP) uptake and adherence amongst Singaporean patients diagnosed with Obstructive Sleep Apnea (OSA), and to evaluate factors correlated with CPAP uptake and adherence. The study involved the retrospective review of medical records of patients of the Integrated Sleep Service of Changi General Hospital (a tertiary referral hospital). These patients underwent a diagnostic sleep study between January 2011 to December 2015 and were diagnosed with OSA. Their medical records were accessed the following information was obtained-age, gender, Body Mass Index (BMI), Epworth Sleepiness Score (ESS), presence of nasal symptoms, Apnea-Hypopnea Index (AHI), choice of initial treatment for OSA (CPAP, surgery, adjunctive therapies, reject treatment), CPAP uptake, CPAP adherence at 1 and 12mths. Table 2 Studies on CPAP acceptance and adherence in Western populations. Source/year
Country
Follow up period
Disease severity
Cohort size
CPAP acceptance
CPAP adherence
Jacobsen et al./2017 [10] Lanza et al./2017 [11] Budhiraja et al./2017 [12] McMillan et al./2014 [13] Ching et al./2013 [14] Nadal et al./2017 [15]
Denmark Italy USA UK Australia/New Zealand Spain
3 years 1 year 6 months 1 year 1 year 6 months
All OSA Severe OSA Severe OSA Severe OSA Moderate and severe OSA Moderate and severe OSA
695 144 394 102 50 191
– – – – – –
78% 87.5% 67.3% 35.3% 46% 75%
2
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severe (AHI ≥30) OSA. CPAP adherence was defined as 4 h/night use, 70% of nights, based on machine report. Patients who did not have a CPAP machine report were considered to be non-adherent, even if they claimed to use their CPAP for > 4 h per day. CPAP uptake is defined as acceptance of CPAP therapy after the initial trial period and obtaining a personal CPAP machine. Patients who had diagnoses other than OSA, such as insomnia, parasomnia, central sleep apnea, mixed sleep apnea, narcolepsy, restless leg syndrome, periodic limb movement disorder and obesity hypoventilation syndrome were excluded from the study. The small number of patients who were issued BIPAP (instead of CPAP) were excluded from the study. All patients underwent in-laboratory level 1 diagnostic sleep studies (Compumedics PS, Melbourne, Australia) which included continuous electroencephalogram, oculogram, electrocardiogram, electromyogram, nasal airflow, thoracic and abdominal respiratory movements, pulse oximetry, snore volume, position and video monitoring. All studies were scored by a Registered Polysomnographic Technologist (RPSGT), certified by the Board of Registered Polysomnographic Technologists in the United States. The American Academy of Sleep Medicine (AASM) 2007 criteria was used. All patients who were prescribed CPAP underwent CPAP counselling prior to a CPAP trial to educate them on the rationale, benefits, common side effects and common technical issues encountered with CPAP. Patients were fitted with an appropriate mask interface (> 95% of patients used a nasal mask). CPAP treatment was initiated with auto-PAP in all cases. Patients were loaned a CPAP machine for a free 1-month trial. A RPSGT would call the patient over the phone 1 week into the trial to check on the patients and assist with any issues affecting CPAP adherence. At the end of the trial, patients who accepted long term CPAP therapy (“CPAP uptake”) would purchase a CPAP machine (via the hospital or through their own channels). Analyses were performed using SPSS 24.0 with statistical significance set at p < 0.05. Logistic regression analysis was performed to evaluate the variables associated with treatment rejection, CPAP uptake after 1-month trial and CPAP adherence at 1 year with odds ratios & 95% CI reported.
Table 3 Characteristics of overall study population (n = 2160). Factor
Results
Gender Age BMI Obese (BMI > 27) ESS
1773 (82.1%) were male and 387 (17.9%) were female 44.7 (range 14–89) 30.0 (range 15–75) 1378 (63.8%) obese Mean 18.6 (range 0–24) 787 (36.4%) had ESS > 10 820 (38.0%) 463 (21.4%) had mild OSA, 583 (27.0%) had moderate OSA and 1114 (51.6%) had severe OSA CPAP trial - 751 (34.8%) Surgery - 288 (13.3%) Adjunctive treatments - 291 (13.5%) Rejected treatment - 830 (38.4%)
Nasal symptoms OSA severity Initial therapy
Note: Adjunctive treatments refer to treatments for OSA other than CPAP or surgery. These are: positional therapy, oral appliance, treatment of allergic rhinitis with intranasal corticosteroids and weight loss.
(p < 0.001). Age, gender, BMI, ESS, presence of nasal symptoms and AHI were not predictive of CPAP uptake after CPAP trial (Table 4 and Fig. 1). 3.3. CPAP adherence at 1 year Following CPAP uptake, 299 out of 381 (78.5%) patients were adherent to CPAP therapy at 1 year. Univariate and multivariate analysis of age, gender, BMI, ESS, presence of nasal symptoms, AHI did not reveal any of these factors to be predictive of CPAP uptake after CPAP trial. CPAP adherence at 1 month was a predictor of CPAP adherence at 1 year (p < 0.001) (Table 4 and Fig. 1). 3.4. Surgery while on CPAP 24 patients underwent surgery during their first year of using CPAP. 11 patients underwent nasal surgery, 10 underwent palatal surgery and 3 underwent combined nasal and palatal surgery. 21 out of the 24 patients (87.5%) were adherent to CPAP at 1 year after undergoing surgery during their first year of CPAP. Univariate analysis did not show surgery during the first year of CPAP use to be predictive of CPAP adherence at 1 year (p > 0.05).
3. Results 3.1. Overall cohort 2160 patients were diagnosed with OSA within the 5-year period. 1773 (82.1%) were male and 387 (17.9%) were female. Mean age was 44.7 years old (range 14–89). Mean BMI was 30.0 (range 15–75). 1378 (63.8%) were obese with BMI > 27. Mean ESS was 18.6 (range 0–24), 787 (36.4%) had ESS > 10. 820 (38.0%) of patients had significant nasal symptoms. 463 (21.4%) had mild OSA, 583 (27.0%) had moderate OSA and 1114 (51.6%) had severe OSA. For initial therapy, 751 (34.8%) patients opted for 1-month long CPAP trial, 288 (13.3%) patients chose surgery, 291 (13.5%) patients chose adjunctive treatments (dental appliance, weight loss, positional therapy, treatment of allergic rhinitis) and 830 (38.4%) patients rejected all forms of treatment (Table 3).
3.5. Treatment rejection Univariate and multivariate analysis showed that older age, higher BMI and normal ESS were correlated with treatment rejection. Age was a predictor, with older patients more likely to reject treatment (p < 0.001). Patients with higher BMI were more likely to reject treatment (p = 0.013). Patients with normal ESS (≤10) were more likely to reject treatment (p = 0.01). Gender, presence of nasal symptoms and AHI were not predictive of treatment rejection (Table 4). 4. Discussion
3.2. CPAP trial and uptake 4.1. CPAP adherence and uptake Out of the 751 patients who underwent the 1-month long CPAP trial, 337 (44.9%) were adherent to CPAP therapy. 381 out of 751 (50.7%) patients took up CPAP therapy by obtaining a personal CPAP unit following the trial period. Out of the 381 patients who took up CPAP, 254 (66.7%) were adherent to CPAP therapy and 127 (33.3%) were not adherent to CPAP therapy during the 1-month trial. Amongst the 370 who completed the CPAP trial but did not take up CPAP, 83 (22.4%) had been adherent to CPAP therapy and 287 (77.6%) were not adherent to CPAP therapy. Univariate and multivariate analysis showed CPAP adherence at 1 month was a predictor of CPAP uptake after trial
78.5% (299 out of 381) of our patients who accepted CPAP therapy were adherent to CPAP at 1 year, making it one of the highest rates of adherence in international literature [1–9]. A possible reason for the high adherence rate is the high cost of CPAP which has to be paid out of pocket may select for patients who are highly motivated to undergo treatment. In addition, the practice of allowing patients a free 1-month CPAP trial period (patients only have to purchase a personal CPAP mask) allows the patients to have sufficient time to experience CPAP therapy prior to making their decision whether to accept or decline 3
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Table 4 CPAP trial, uptake and adherence. Outcome
Result
CPAP 1-month trial CPAP adherence at 1 month
751 patients 337 out of 751 patients (44.9%) were regular users 381 out of 751 patients (50.7%) 254 patients (66.7%) were regular users 127 patients (33.3%) were not regular users 370 out of 751 patients (49.3%) 83 patients (22.4%) were regular users 287 patients (77.6%) were not regular users 299 out of 381 (78.5%) were regular users
CPAP uptake after trial
CPAP non-uptake after trial
CPAP adherence at 1 year
Factors associated with outcomes
Results
Univariate and multivariate analysis of age, gender, BMI, ESS, presence of nasal symptoms, AHI CPAP adherence at 1 mth Univariate and multivariate analysis of age, gender, BMI, ESS, presence of nasal symptoms, AHI CPAP adherence at 1 mth
Not predictive of CPAP uptake (p > 0.05) Predictive of CPAP uptake (p < 0.001) Not predictive of CPAP adherence at 1 year (p > 0.05) Predictive of CPAP adherence at 1 year (< p < 0.001)
Patients with OSA (n= 2160)
CPAP 1 month trial 751 patients (34.8%)
Surgery 288 patients (13.3%)
Adjunctive treatments 291 patients (13.5%)
Rejected all treatments 830 patients (38.4%)
Adherent to CPAP (1 month) 337 patients (44.9%)
CPAP non uptake 370 patients (49.3%)
Non-adherent to CPAP (1 year) 82 patients (21.5%)
CPAP uptake 381 patients (50.7%)
Adherent to CPAP (1 year) 299 patients (78.5%)
Fig. 1. Choice of initial treatment in patients with OSA, CPAP trial, uptake, adherence at 1 month and 1 year in a cohort of Singaporean patients with OSA.
also unable to utilize their Medisave funds (mandatory national healthcare savings scheme) and few local insurance companies cover the cost of a CPAP machine. Hence, patients are willing to undergo a diagnostic sleep study but many decline CPAP therapy due to the costs involved. Authors from other Asian privately funded healthcare systems report facing similar issues [5,8]. Other reasons why patients declined CPAP therapy after CPAP trial include: inconvenience of treatment, poor disease perception (did not understand the need for treatment) or decision to switch to another treatment for OSA [3].
CPAP therapy, thereby selecting for patients who are able to tolerate CPAP. However, our patient cohort had a low CPAP uptake rate after CPAP trial of 50.7% (381 out of 751). Out of the entire patient cohort, only 17.6% (381 out of 2160) accepted CPAP therapy, of which only 13.8% (299 out of 2160) were adherent to CPAP therapy. Several factors could possibly account for this. The high cost of CPAP acts as a barrier to uptake of CPAP therapy after the diagnosis of OSA. In the Singaporean healthcare system, the diagnosis of OSA (medical consultations and inpatient diagnostic sleep studies) is funded by public funds or insurers, while CPAP therapy is not. On the other hand, most patients are required to purchase CPAP machines with cash. The cost of a CPAP machine averages SGD$1500–S$2000 (USD$1100–1500), which is about half of the median monthly salary of SGD $4232 (2017 data). Government subsidies are only available to the very needy. Patients are
4.2. Treatment rejection and untreated disease burden Our patients had a high upfront treatment rejection rate of 38.4% (830 out of 2160), who declined all OSA therapy at the initial consultation after the diagnostic sleep study or did not even turn up. The 4
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actual treatment rejection rate is likely to be higher - the majority of patients who underwent a CPAP trial but did not accept CPAP therapy ended up rejecting all treatments. The patients who opted for alternative treatments (including weight loss, oral appliances, treatment of allergic rhinitis, positional therapy) may or may not have been adherent to their chosen treatment, and their chosen treatment may or may not have been effectively treating their OSA. In the group of patients who opted for surgery, most declined a postoperative sleep study due to the time and cost involved, or if their symptoms had resolved. Thus, the burden of untreated disease is significant. Analysis of our data showed that older patients, patients with higher BMI and patients with normal ESS were more likely to reject treatment for OSA. Awareness of patients at risk of rejecting treatment can allow healthcare providers to focus their efforts on these patients to increase awareness of disease.
but this was not statistically significant, possibly due to small sample size and high overall rate of CPAP adherence.
4.3. Predictors of CPAP adherence
4.7. Strengths of the study
In our study - adherence to CPAP at 1 month is predictive of CPAP uptake as well as CPAP adherence at 1 year. This corroborates multiple studies which have shown that early patterns of CPAP usage are predictive of long term usage [2,16]. However, from our data-age, gender, BMI, ESS, presence of nasal symptoms and AHI were not predictive of CPAP uptake or CPAP adherence at 1 year. In several other studies, disease severity as measured by AHI and ESS has been shown to be correlated to CPAP adherence, with patients with higher AHI and ESS more likely to use CPAP. Age, gender and BMI are inconsistently correlated with CPAP adherence [1,3,17–19]. Objective measures of nasal resistance have been correlated with lower rates of CPAP uptake and adherence [20–21]. The lack of correlation between these factors and the outcome of CPAP uptake and adherence in our study does not show that they are not associated, but rather reflects that multiple factors can interact and influence a patient's decision to accept and adhere to CPAP.
Our study has the distinction of having the largest patient cohort size amongst studies conducted in Asian populations [3–9]. In addition, our assessment of CPAP adherence relies on CPAP machine data, as selfreported CPAP usage has been shown to be inaccurate and over-estimates actual CPAP use [16–19].
4.4. Improving CPAP adherence
5. Conclusion
Several steps have been taken improve the CPAP adherence amongst our patients at the Integrated Sleep Service of Changi General Hospital. Increased patient and spousal education efforts take place through detailed CPAP education sessions and written information handouts prior to CPAP initiation. Patients who have tried CPAP at home and are facing issues are offered the option of a 1-night CPAP titration study in the sleep laboratory to allow for onsite support and troubleshooting. Patients can also be referred for Cognitive Behavioural Therapy by a trained psychologist to help them to overcome psychological and social barriers to CPAP therapy. Patients using CPAP with severe nasal obstruction not responding to medical therapy are offered nasal surgery by the ENT surgeon [1,21].
Singaporean patients who accept CPAP therapy after an initial 1month CPAP trial will generally be adherent to CPAP therapy (78.5%, 299 out of 381). Initial patterns of CPAP usage (adherence at 1 month) is predictive of long term (1 year) CPAP adherence (p < 0.001). However, only a small proportion of the entire patient cohort accepted CPAP therapy (17.6%, 381 out of 2160), of which only 13.8% (299 out of 2160) were adherent to CPAP therapy at 1 year. Upper airway surgery in selected patients may improve CPAP adherence.
4.5. Surgery
Conflict of interest
A significant proportion of patients (13.5%, 291 out of 2160) opted for surgical treatment as an initial treatment, despite a trial of CPAP and other non-surgical treatments being advocated. Possible reasons for patients opting for surgery as an initial treatment include: availability of funding (from government subsidies, insurance coverage and Medisave), desire for a swift solution and aversion to be dependent on a long-term therapy. Multiple studies have found that upper airway surgery in select patients can improve CPAP adherence [22–24]. In our study, a small number of patients who completed a CPAP trial and proceeded to uptake CPAP therapy also underwent surgery during the first year of using CPAP (24 out of 381 patients, 6.3%). For these patients, the goal of surgery was to facilitate CPAP delivery and adherence by addressing anatomical sites of obstruction. These patients had a higher rate of CPAP adherence compared to the overall cohort (87.5% versus 78.5%),
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
4.6. Patients with mild OSA Patients with mild OSA do not necessarily require CPAP and we advocate other treatments such as surgery, dental appliances, weight loss and positional therapy to this group. However, some patients do request for CPAP due to personal preference and we allow them to experience a trial of CPAP therapy. In our cohort, 49 out of the 463 (10.6%) patients diagnosed with mild OSA opted for CPAP as an initial therapy. After the 1-month CPAP trial, 23 out of the 49 took up long term CPAP therapy, and 19 out of 23 patients were adherent to CPAP at 1 year.
4.8. Limitations of the study Our study has several limitations. Firstly, the follow up duration of 1 year is a relatively short time period, given that OSA is a chronic disease. It is possible that given a longer follow up period, the CPAP adherence rate would have reduced. Secondly, only the patient's initial choice of treatment is recorded and crossing over of patients between the various treatment options is not reflected. Thirdly, there was limited evaluation of the numerous known predictors of CPAP adherence in view of the study's retrospective design.
Funding No funding was received for this research.
Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/ or national research committee (name of institute/committee) and with the 1964 Helsinki declaration and its later amendments or comparable 5
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ethical standards. For this type of study formal consent is not required. Singhealth Combined Institutional Review Board (CIRB) ethical approval was sought and obtained (Reference: 2017/2819) prior to commencement of the study.
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