Original ArticleFindings of a Berlin Questionnaire survey: Comparison between patients seen in an asthma clinic versus internal medicine clinic☆,☆☆
Introduction
Obstructive sleep apnea (OSA) is increasingly common, with recent estimates suggesting a prevalence of 5% [1]. Asthma prevalence has also risen, and it is estimated that 7.5% of adults in the United States are asthmatics [2]. Asthmatics are known to have disturbed and poor sleep, often attributed to nocturnal worsening of their asthma [3], [4]. A survey study found that 39% of patients with various degrees of asthma had disturbed sleep on a nightly basis [5]. Asthmatics also often report increased daytime sleepiness [3], [6]. In a large community-based survey of respiratory symptoms, asthmatics reported a higher prevalence of snoring as compared to the general population [7]. As snoring and daytime sleepiness are common symptoms in OSA, these data suggest a possible association between these two conditions. Recently, it has been suggested that the sleepiness reported by asthmatics is associated with sleep apnea risk and not asthma severity [8]. Of interest, a study of 788 children who underwent in-home unattended sleep studies found an association between sleep-disordered breathing and a history of wheezing, but not a parent-reported diagnosis of asthma [9].
It has yet to be conclusively determined whether asthma and OSA are simply two common conditions with similar symptoms or whether there is a pathophysiologic or causal association between the two. Recent data suggests that OSA is linked to increased bronchial hyperresponsiveness [10] and is an independent risk factor for asthma exacerbations [11]. Furthermore, continuous positive airway pressure (CPAP) treatment of OSA in asthmatics decreases nocturnal asthma symptoms [12], [13] and may improve daytime peak flows [14]. Given these findings and the recognition that OSA is underdiagnosed [15], it is clinically relevant to determine the prevalence of OSA in the asthma population. We hypothesized that, utilizing a validated OSA screening tool, the prevalence of OSA symptoms and thus risk for OSA would be greater in asthmatics when compared to a general internal medicine population.
Section snippets
General study design
A prospective questionnaire survey study was performed in the Asthma Clinics and Internal Medicine Clinics at MetroHealth Medical Center (MHMC) in Cleveland, Ohio. MHMC is an urban academic hospital that serves as the county hospital for Cuyahoga County. The study was performed between October of 2002 and September of 2003. The study was approved by the Institutional Review Board of MHMC. All subjects provided informed consent to participate.
Subjects
We prospectively studied 505 patients and assessed
Results
Of 585 subjects who were approached, 573 (98%) agreed to participate and 563 subjects met the criteria for inclusion (see Fig. 1). Of these, 379 were returned completed from the Internal Medicine Clinics and 184 were returned completed from the Asthma Clinics. Subjects with self-reported OSA were excluded from both clinics (13 subjects in the Internal Medicine Clinics and 7 subjects in the Asthma Clinics). Overall, the refusal to participate rate and the percentage of subjects with reported OSA
Discussion
The primary finding from this study, that asthmatics are more likely to report symptoms suggestive of OSA than non-asthmatics, provides further support that there is an association between these two conditions. While earlier studies suggested that disturbed sleep in asthmatics was predominantly related to poorly controlled nocturnal asthma [3], [6], [20], more recent studies have found that symptoms of OSA, such as snoring and witnessed apneas [8], [21], [22], are common in this population. The
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This work was previously presented, in part, at the American Thoracic Society Meeting, Orlando, FL, May 25th, 2004.
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The authors have no financial or other potential conflicts of interest to report.