4 | DISCUSSION
The main finding of our study was that sleep dissatisfaction, short
sleep, and asthma were all associated with an increased risk of suicidal
ideation. However, long WCUS was associated with a decreased risk of
suicidal ideation in Korean adolescents with asthma. To the best of our
knowledge, this is the first study to investigate the relationship
between WCUS and suicidal ideation in adolescents with asthma after
adjusting for multiple potential confounding factors.
Our results indicate that short sleep duration is significantly
associated with suicidal ideation in adolescents with asthma.
Approximately 8-10 hours and 7-9 hours of sleep are considered
sufficient for teenagers and young adults,
respectively.20 In general, adolescents are considered
to be chronically sleep deprived with decreased total sleep duration and
increased daytime sleepiness.12 This chronic sleep
deprivation is due to a variety of factors including decreased parental
control, inconsistent bedtimes, increased schoolwork, poor sleep hygiene
(e.g., caffeine use late in the day, technology in the bedroom,
smartphone overuse), and a discordance between biological circadian
rhythms and early school start times.12 In Korea, most
middle- and high-school classes start before 8:30 AM. And many Korean
adolescents attend private academic institutions and study late at night
even on the weekends.15 These students face strong
psychosocial pressure to attain sufficient grades for admission into
prestigious universities.7,15 The link between short
sleep duration and suicidal ideation in adolescents with asthma is
complex and not fully understood. However, there are several possible
explanations for this association.
First, sleep deprivation itself is considered to be a stress-inducing
factor for adolescents with a higher risk of several mental disorders
such as behavioral disorders,22 substance
abuse,22 depression,22,23 and
suicidality.22 In adolescents with asthma who have
sleep problems commonly, including prolonged sleep onset latency,
difficulty in falling asleep, frequent nocturnal awakenings, daytime
sleepiness, and early awakenings,24 even when their
asthma symptoms are well controlled,12 short sleep
duration may be associated with higher risk of suicidal ideation
In addition, given its long-term disease course, asthma is associated
with depression due to the need for chronic treatment and the repeated
exacerbations that may themselves cause
hopelessness.25 The chronic nature of this disease may
lead to increased asthma symptoms through risk-taking behaviors
(smoking, drinking, non-adherence to medication and poor illness control
in general)25 and consequently increased suicide
risk.26,27 As it is known that people with asthma have
a significantly increased risk of suicidal ideation,28suicidal ideation may become more prevalent in adolescents with asthma
when they become sleep deprived.
Third, in patients with asthma, the prevalence of obstructive sleep
apnea (OSA) and sleep disordered breathing (SBD) is consistently higher
than it is in the population without asthma.24,29,30Asthma seems to be a consistent and independent risk factor for SDB (OR
= 1.9 [1.69-2.18]).29 Gutierrez et al. found that
maximal percentage of rapid eye movement (REM) SpO2desaturation, and the REM obstructive apnea–hypopnea index (OAHI) were
significantly higher in asthmatic children with OSA than they were in
subjects with OSA alone.31 These findings may result
in sleep deprivation in adolescents with asthma, and then may be
associated with a high risk of suicidal ideation related to the
aforementioned negative mental health state in asthma.
Another notable finding in our study was that adolescents with asthma
were more likely to be night owls on both weekdays and weekends, while
be early larks only on weekdays. As we hypothesized, adolescents with
asthma had shorter weekday sleep duration and longer weekend sleep
duration than did those without asthma. These findings may be explained
by the sleep characteristics and problems of asthma itself, including
nocturnal symptoms and the aforementioned educational uniqueness in
Korea. These differences may also be related to the longer WCUS in
adolescents with asthma than that of those without asthma for sleep debt
compensation. Because individual sleep needs vary, WCUS is not only an
indicator of the degree of insufficient weekday
sleep,5 but also is a compensatory behavior to cope
with weekday sleep debt.32 A recent study found that
the risk for anxiety and depression was higher among adults who did not
have WCUS than it was among those who did.32 Long WCUS
was associated with a decreased frequency of asthma and depression in
Korean adolescents.5,15 However, it is unclear whether
WCUS has advantageous effects on emotional states of adolescents with
asthma, because sleep hygiene guidelines recommend regularizing sleep
time and wake-up time15,20 In particular, the
association between suicidal ideation and WCUS in adolescents with
asthma has not been evaluated previously . To the best of our knowledge,
our results are the first to show that sufficient WCUS duration (of
≥2hr) may play a protective role against suicidal ideation among
adolescents with asthma. However, this finding does not mean that
adolescents with asthma should sleep longer on the weekends than they do
during weekdays. Nevertheless, it is important for adolescents with
asthma to achieve sufficient sleep time during the weekend in the way
that WCUS is an indicator of insufficient weekday sleep.
There are several methodological limitations in this study that must be
noted. First, our results are subject to recall bias, because we used
self-reported data collected via the internet. Studies using more
objective assessments of sleep, such as polysomnography or actigraphy,
are needed to avoid this limitation. Second, we only collected data at a
single point in time by asking about typical sleep pattern over the
preceding week. Weekend sleep duration may vary depending on the
situation of the following week (e.g. school examination). Longitudinal
studies are needed to clarify our findings, as asthma control and sleep
patterns may change throughout the school year. Third, this study was
cross-sectional in design; therefore, we were unable to establish a
causal relationship between associated sleep factors and suicidal
ideation in adolescents with asthma. Well-controlled prospective studies
are necessary to confirm the results of the present study. Fourth, we
did not analyze asthma management, treatment modalities, or asthma
severity because such information was lack and only the lifelong
diagnosis of asthma was evaluated in the survey. This omission may have
led to the misclassification of asthma. In addition, despite adjusting
for various potential confounders, the survey did not assess other
significant factors that have been associated with poor sleep quality,
such as OSA, snoring, nocturnal gastroesophageal reflux, internet or
smartphone use time, and caffeine or drug use.
Despite these limitations, this study also has several strengths and
important clinical implications for adolescents with both asthma and
sleep problems. This was a nationwide, government-directed survey with a
high response rate (96.2%). To the best of our knowledge, our study
included the largest number of participants among similar studies. A
socioeconomically diverse sample with an equal proportion of middle
school and high school students (400 schools each annually) were
represented. All of the analyses in this study were based on sample
weights and were adjusted for the complex sample design of the survey.
Almost all participants had the same ethnic background, which minimizes
other possible confounding factors. These study characteristics also
mean that our results are generalizable to the overall Korean
population. Most of all, this research was the first to identify
associated sleep factors associated with suicidal ideation in
adolescents with asthma. No prior study had evaluated the relationship
between WCUS and asthma. The public health implications of our findings
can be applied at the educational and practical levels. A recent study
demonstrated that adolescents were able to successfully extend sleep
duration with sleep hygiene education.33 This simple
intervention would likely be beneficial for adolescents with
asthma.12 From an educational perspective, strategic
interventions to reduce academic stress on Korean adolescents should be
seriously considered, such as a more late start to classes. Health care
professionals, including pediatric allergists, require a greater
awareness of the risk of mental health problems and suicidality in
adolescents with asthma. This is particularly true in those with
concurrent sleep problems. When treating adolescents with asthma, these
patients require a holistic approach with a more accurate assessment of
associated sleep factors related to suicidality.