Adherence to CPAP in summer to autumn predicts self-reported common cold symptoms in patients with obstructive sleep apnea in winter: A prospective observational study

Highlights

• Better CPAP adherence was associated with fewer days with common cold symptoms.

• The association between them was more pronounced in the young to middle-aged group.

• Sleep duration and insomnia had negligible association with common cold symptoms.

Abstract

Objective

We conducted a prospective observational study to determine the relationship between adherence to continuous positive airway pressure (CPAP) and susceptibility to the common cold in moderate-to-severe obstructive sleep apnea (OSA) patients.

Methods

We prospectively investigated the number of days with common cold symptoms from November 2019 to February 2020. The rate of CPAP use for 4 h/night in the preceding four months (July to October 2019) was used as a measure of CPAP adherence. Multiple generalized linear models were used to evaluate the association to days of common cold symptoms after controlling for demographic variables, habitual short sleep duration, and insomnia severity.

Results

We included 123 outpatients (median age 63 years) with moderate-to-severe OSA treated with CPAP. In the multivariate generalized linear model, better CPAP adherence was independently significantly associated with days with fewer common cold symptoms (β = −0.248, P = 0.031); meanwhile, the severity of insomnia and habitual short sleep duration was not significantly associated with it. Subgroup analyses revealed that the association between CPAP adherence and days with common cold symptoms was also significant in young to middle-aged (<65 years) participants (β = −0.407, P = 0.005). In contrast, the association was negligible in older (≥65 years) participants.

Conclusions

CPAP adherence may be protective against viral infections in patients with moderate-to-severe OSA. This effect appears to be more pronounced in young to middle-aged patients with OSA.

Introduction

Nighttime sleep is considered to restore immune processes [1,2]. Sleep loss can impair host defenses and affect the susceptibility to pathogens such as viruses and bacteria. Some previous studies have reported the association of short sleep duration with an increased risk of contracting the common cold [[3], [4], [5]]. Not only quantitative but also qualitative disturbances in sleep can adversely affect immune function [5]. Chronic insomnia is reportedly associated with impaired immune function [6,7]. Another common disorder that causes problems with sleep quality is obstructive sleep apnea (OSA). OSA is characterized by functional obstruction of the upper airway, resulting in decreased blood oxygen saturation at night, subsequent sleep fragmentation, and daytime impairments [8]. Especially in severe OSA, polysomnography shows marked nocturnal sleep fragmentation [9]. OSA triggers a cascade of chronic low-grade systemic inflammatory processes through oxidative stress because of excessive production of reactive oxygen species and induction of inflammatory mediators and pro-inflammatory cytokines [10], similar to the dynamics induced by sleep deprivation [11]. In the clinical setting, the possibility of increased infection risk has been reported because of OSA [[12], [13], [14]].

Patients with moderate-to-severe OSA are treated with continuous positive airway pressure (CPAP), which improves sleep architecture [15], and physical conditions such as resistant hypertension [16] and insulin resistance [17]. Although two meta-analyses have shown that CPAP improves inflammatory markers in the blood of OSA patients [18,19], the effect of CPAP on impaired immune function in OSA patients has not been evaluated. In addition to a report of an association between influenza morbidity and OSA [14], a recent study found that untreated and treated OSA patients with poor CPAP adherence are more frequently hospitalized for influenza than those with good CPAP adherence [20]. However, evidence about the infection-protective effects of CPAP in patients with OSA is still limited. Thus, this prospective observational study on patients with moderate-to-severe OSA aimed to elucidate the relationship between CPAP adherence and the risk of developing a common cold. Investigating the common cold as a target variable ignores some complexity because the common cold is caused by a variety of viruses [21]. Nevertheless, given its low invasiveness and high feasibility, an observational study on susceptibility to the common cold may help investigate the relationship between human immune mechanisms and sleep in a real-world setting.

We hypothesized that patients with good CPAP adherence would have a lower risk of contracting the common cold than those with poor CPAP adherence, even after controlling for habitual short sleep duration and insomnia symptoms. The common cold causes nasal obstruction and pharyngeal symptoms, which may directly affect the patient and prevent them from using CPAP. For this reason, under the presumption that CPAP adherence in summer/autumn would reflect adherence throughout the year, we examined whether CPAP adherence during the summer/autumn season was associated with the number of days with common cold symptoms in winter. Considering that sleepiness and decrease in health-related quality of life because of OSA are more pronounced in younger patients than in older ones [22,23], we also focused on differences by age group in the association between CPAP adherence and common cold symptoms; we conducted a subgroup analysis by dividing the patients into two groups, young to middle-aged (<65 years) and older (≥65 years) [24].