Correlates of daytime sleepiness in patients with asthma

Abstract

Background and purpose

Patients with asthma often complain of daytime sleepiness, which is usually attributed to a direct effect of asthma on nocturnal sleep quality. We investigated this and other potential explanations for daytime sleepiness among asthmatics.

Patients and methods

One hundred fifteen adult asthmatics were assessed for perceived daytime sleepiness (one question item), subjective sleepiness (Epworth Sleepiness Scale score, ESS), obstructive sleep apnea risk (Sleep Apnea scale score within Sleep Disorders Questionnaire, SA-SDQ), asthma severity step, relevant comorbid conditions, and current asthma medications.

Results

Among all subjects, 55% perceived excessive daytime sleepiness and 47% had ESS > 10. Most subjects reported snoring (n = 99, or 86%) and many snored habitually (n = 44, 38%). The ESS correlated with SA-SDQ (P < 0.0001), male gender (P = 0.01), and asthma severity step (P = 0.04). In a multiple regression model, the ESS was independently associated with SA-SDQ (P = 0.0003) and male gender (P = 0.02), but not with asthma severity step (P = 0.51). There were no correlations between ESS and age, body mass index (BMI), forced expiratory volume in one second as percent of predicted value (FEV₁%), comorbidities, or medication used to treat asthma.

Conclusions

Sleepiness is common in asthmatics and may reflect occult obstructive sleep apnea more often than effects of asthma itself, other comorbid conditions, or asthma medications.

Introduction

Daytime sleepiness is a particularly frequent complaint in patients with asthma [1], [2]. Daytime sleepiness has a negative impact on quality of life, work performance, and risk for motor vehicle crashes or work-related accidents [3]. In general, daytime sleepiness is often the result of poor sleep quality, and asthmatics do commonly complain about difficulty with initiation [1], [4] and maintenance of sleep, especially in the early morning [1], [5]. Such sleep disturbances become more frequent with increased nocturnal asthma symptoms [1]. Nocturnal wakefulness correlates with daytime airways obstruction, as measured by forced expiratory volume in one second as percent of predicted value (FEV₁%) [1]. Sleep studies in asthmatics have provided some objective evidence of poor sleep quality as evidenced by a reduced sleep time, delayed latency to sleep, frequent awakenings after sleep onset, early morning arousals and reduced slow wave sleep [4], [6]. Therefore, daytime sleepiness in asthma is often thought to be the consequence of a direct effect of nocturnal asthma on sleep quality.

Both increased subjective sleepiness and poor sleep quality scores were documented recently in a large population of asthmatics [7], but two therapeutic strategies for asthma failed to improve subjective sleepiness and sleep quality scores [8]. These results suggest that other possible reasons for daytime sleepiness in asthmatics also should be considered. Excessive daytime sleepiness (EDS) is one of the most common presenting symptoms of obstructive sleep apnea (OSA), in itself a common and frequently unrecognized condition [9], [10]. Snoring is frequent in both OSA patients and asthmatics [2], [11], [12]. Recently, in a sample of 22 difficult-to-control asthmatics, daytime sleepiness was reported by 20 (90.9%) of the subjects and OSA was demonstrated by polysomnography in 21 (95.5%) of them [13]. Furthermore, asthma frequently coexists with allergic rhinitis and chronic sinusitis [14], gastroesophageal reflux disease (GERD) [15], obesity [16], and psychopathology such as anxiety, depression and panic disorders [17], [18], all of which are known to be associated with daytime sleepiness [3], [5], [19], [20]. The medications commonly used to treat asthma tend to have stimulating, anxiety-provoking or mood-depressing properties [5], [21], [22] that could interfere with sleep quality and exacerbate daytime sleepiness.

Previous studies of sleepiness in asthma have been limited by reliance on patient-reported asthma diagnosis or have not included information on comorbid conditions and medications that could influence sleepiness. We therefore studied a sample of medically well-characterized asthmatics with validated survey measures to examine possible reasons for EDS. In particular, we hypothesized that unrecognized OSA is an important contributor to EDS in asthmatics.