1 | INTRODUCTION
Although the prevalence of asthma has started to plateau and even decline in adolescents in Western countries,1 asthma remains one of the most common chronic pediatric diseases with a significant impact on quality of life (QoL).2 One of the ways that asthma affects quality of life is through its impact on sleep, including more frequent nighttime awakenings due to night asthma attacks and sleep-disordered breathing.3-7 Nocturnal asthma is a common complication, with ≥90% of the episodes of dyspnea in asthmatics occurring at night.8 These nocturnal asthma symptoms typically occur between 04:00 and 06:00 h.8 The most studied causes and contributing factors to asthma exacerbations at night include night-time physiological changes (e.g., accidental coughing, wheezing, and breathing difficulties),6,7,9 and circadian changes in ventilation, airway responsiveness and inflammation, mucociliary clearance, ventilatory responses to hypercapnia and hypoxia, and hormone levels.6 Eventually, nocturnal symptoms trigger awakening during sleep, which impairs daily activities, increases morbidity, induces psychometric changes, reduces QoL and these changes can even contribute to suicidality.10 However, the association between sleep duration and asthma is conflicting. Some studies have found that children with asthma have generally shorter sleep durations than do those without asthma,11 while other studies have not found such differences in adolescents.12 Another report found that sleep duration in asthmatics is significantly longer than it is in non-asthmatics.13 Recently, compared with 7–8 h of sleep per night in adolescents, both short sleep duration (sleeping for <7 h) and long sleep duration (sleeping for ≥9 h) had 1.22 (95% CI 1.07, 1.40) and 1.31 (1.06, 1.63) times higher OR of asthma, respectively.7
Weekend catch-up sleep (WCUS) is defined as sleep time during the weekend that exceeds sleep time on weekdays.5,14 WCUS is not only an indicator of insufficient weekday sleep, but also a compensatory phenomenon for weekday sleep debt.5,14Adolescents tend to sleep for shorter durations during the night and exhibit a delayed sleep phase than do children.15Adolescents also tend to sleep less than children do during school days because of the pressure of school work. In order to compensate for insufficient weekday sleep over the entire week, adolescents then tend to sleep more on the weekends.9,15 The effects of WCUS on one’s overall health are conflicting. Some studies have found that WCUS is associated with a lower risk of hypertension,14 obesity prevention in adults,16 and lower frequency of asthma in adolescents.5 In contrast, WCUS had adverse effects on executive functions,17 and contributes to suicidal attempts and self-injury in children and adolescents.18 Sleep disturbances in asthma are well known. However, to the best of our knowledge, no prior studies have addressed the influence that WCUS has on suicidal ideation in adolescents with asthma. Current suicidal ideation is considered one of the most important clinical predictors of future attempts and death by suicide.19 Therefore, it is crucial to identify the sleep factors that are associated with suicidal ideation in adolescents with asthma in order to reduce suicide in this group.
Given this background, we hypothesized that adolescents with asthma are more likely to have shorter total and weekday sleep duration than are peers without asthma. We also suspected that adolescents with asthma would have longer weekend sleep duration and longer WCUS to compensate for their school day sleep deprivation than would adolescents without asthma. This study had two aims. First, we investigated and compared the differences in the clinical characteristics, sleep pattern, and mental health status in adolescents with and without asthma. Second, we identified the associated sleep factors for suicidal ideation in adolescents with asthma. This second step was the main purpose of this study. Therefore, this study was conducted to investigate the association between sleep duration and WCUS with suicidal ideation in adolescents with asthma in a nationally representative Korean dataset.