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Prevalence of Obstructive Sleep Apnea in Outpatient Cardiology Clinic
Study Questions:
How common is obstructive sleep apnea (OSA) in a large consecutive sample from cardiology clinics?
Methods:
Consecutive patients from a single tertiary center were recruited from multiple subspecialty (hypertension, arrhythmia, heart failure, and valvular) clinics. Patients were screened for OSA using the validated Berlin questionnaire. A subset of subjects was randomly selected to undergo portable home sleep tests to objectively determine OSA, defined as an apnea-hypopnea index ≥15 events/hour.
Results:
A total of 510 patients were evaluated and 10 (5 incomplete data and 5 lost to follow-up) were excluded. Average age was 59 ± 13 years, and average body mass index (BMI) was 28.2 ± 5.3 kg/m2. Only 13 (3.1%) had a previous diagnosis of OSA and 258 (51.6%) were at high risk for OSA, based on survey questionnaire. Less than half (n = 6) of the patients with known OSA were receiving specific therapy. The prevalence of a high-risk screening score for OSA was similar among all the cardiology clinics. The frequency (38%) of excessive sleepiness based on Epworth Sleepiness Scale was not as high as OSA diagnosis by Berlin questionnaire. In an adjusted logistic model, only gender (male) and BMI were independently associated with physician diagnosed and treated OSA.
Conclusions:
The authors concluded that despite a growing population at risk for and recognition of sleep breathing disorders associated with cardiovascular disease, OSA is underdiagnosed in a busy tertiary cardiology practice.
Perspective:
OSA is underdiagnosed and therefore undertreated in cardiology clinics, despite a growing body of evidence associating OSA with cardiovascular risk. There are many reasons for the underdiagnosis, including lack of knowledge, costs/burden to diagnosis, and access/reluctance to treatment. This study was not designed to determine the sensitivity or specificity of the Berlin questionnaire for diagnosing OSA. It is not yet clear which screening tool is best to diagnose OSA in this population. To date, observational studies have concluded a positive effect of continuous positive airway pressure (CPAP) therapy on cardiovascular events. However, many clinicians are awaiting large randomized clinical trials demonstrating a positive impact of OSA therapy on adverse cardiovascular events.
Keywords: Apnea, Arrhythmias, Cardiac, Body Mass Index, Continuous Positive Airway Pressure, Disorders of Excessive Somnolence, Heart Failure, Hypertension, Outpatients, Risk Factors, Sleep Apnea, Obstructive, Sleep Apnea Syndromes
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