In this study, we found a substantial burden of both nighttime asthma symptoms and poor sleep among urban children with significant asthma. Overall, 59% of children had persistent nighttime asthma symptoms, and nearly half (46%) of children had at least one night per week of inadequate sleep. Children’s sleep quality, indicated by the total sleep score on the CSHQ and several subscales, decreased as their nocturnal asthma symptoms increased. The likelihood of the child having inadequate sleep, the parent having lost sleep and poorer parental quality of life incrementally increased as the frequency of nocturnal asthma symptoms increased. Importantly, we found that the mean total sleep score for children in each asthma severity level was above the clinically significant CSHQ cut-off of 41, indicating pervasive sleep disturbances among this population of children with asthma.
A few prior studies have assessed the relationship between sleep disturbance and asthma. Stores et al. explored both subjective and objective sleep disturbances among children with nocturnal asthma, compared to a non-asthmatic control group.5
Compared to controls, children with nocturnal asthma experienced worse sleep in both polysomnography tests and questionnaires. They also found improvement in sleep after treatment of the nocturnal asthma symptoms. Similarly, Sadeh et al. explored sleep disturbances among children with well controlled asthma using wrist actigraphs to measure sleep disturbances and peak-flow meters to measure pulmonary function.8
The investigators found that well controlled asthmatic children experienced poorer sleep quality compared to controls, and peak-flow measures were correlated with sleep quality. However both of these studies were limited by small sample sizes and targeted recruitment from respiratory clinics. Our study is unique in assessing sleep disturbances among a large community sample of young, urban school children with significant asthma symptoms. Unlike previous studies, we examined sleep quality in relation to varying degrees of asthma severity and included important covariates, such as parent depression and smoke exposure. Further, our study explored the burden of nocturnal asthma symptoms on both children and families by considering various forms of childhood sleep disruption, parental sleep and quality of life.
Our use of the Children’s Sleep Habits Questionnaire (CSHQ) allowed for collection of information about sleep from a validated sleep quality measure for school-aged children. It was designed to provide comprehensive information including both clinical sleep problems and parent-reported individual sleep concerns that may fall outside of clinical definitions of sleep disorders.11
The use of a sleep quality scale in this group allows for a thorough base of information on the variety of ways that sleep problems may manifest among children with asthma.
Overall, we found that children with moderate to severe nocturnal asthma symptoms had significantly worse sleep scores on several sleep subscales including night wakings, parasomnias, and sleep disordered breathing. Previous research has shown that night wakings in children can significantly impact daytime functioning for both children and their parents. This can include daytime sleepiness, increased behavior problems, decreased neurocognitive functioning and family stress.21
Further, parasomnias have often been associated with negative outcomes, particularly daytime sleepiness,22
and the relationship between sleep disordered breathing and behavior problems also has now been well documented.23–26
Importantly, sleep problems in early life have been linked to emotional and behavioral difficulties, including anxiety, depression, aggressive behaviors and attention problems in adulthood.4
Among children with asthma, sleep disturbance due to nocturnal symptoms can greatly influence health and wellbeing, and may contribute significantly to their disease burden. Previous studies have shown that children who suffer from nocturnal asthma symptoms have negative outcomes in daytime functioning. Nocturnal asthma symptoms are associated with both poorer school attendance and school performance.3
Possibly linked to increased school absence, asthmatic children have been found to have poorer school performance and increased risk of learning difficulties compared to their healthy counterparts.27, 28
This negative effect may be especially pronounced in lower-income asthmatic children who are at greater risk of grade failure.27
Additionally, exploratory studies indicate that sleep disturbances in children with nocturnal asthma may affect cognitive functioning as well as mood and behavior.5
Nocturnal asthma symptoms may also affect the functioning of the parent or caregiver. Prior studies have shown that parents of children with frequent nocturnal symptoms are more likely to miss work which may result in lost wages.3
Further, parents experiencing sleep disturbances related to their child’s illness may have increased daytime fatigue themselves as well as negative mood.6
We found that parents of children with frequent nighttime symptoms reported more nights of lost sleep as well as lower quality of life, even when controlling for depressive symptoms.
Exposure to environmental tobacco smoke has been shown to be an important factor influencing both nocturnal asthma symptoms and sleep quality. In a recent study, Yolton et al. found that sleep is negatively affected by environmental tobacco smoke exposure among asthmatic children.20
Similarly, Morkjaroenpong et al. indicate that nocturnal symptoms are particularly sensitive to ETS.29
Since as many as 50% of urban children with asthma live with a smoker, smoke exposure likely is a very pertinent factor in amplifying sleep difficulties in this population.16, 30
Our findings further support the contribution of ETS to nocturnal asthma symptoms and reinforce the need for further investigation into the relationship between ETS and sleep difficulties among urban children with asthma.
The importance of nocturnal asthma symptoms is highlighted in the national asthma guidelines, since the presence of nighttime symptoms receives greater severity weighting compared to the other symptoms.10
Many parents may underreport their children’s and their own sleep difficulties to primary medical care providers, which may lead to a lack of awareness and subsequent inadequate prescription of preventive therapy.31, 32
The goals of asthma therapy specifically include helping individuals with asthma control their symptoms so that they can sleep well. Clearly, these goals are not being met by numerous individuals, and our study adds to the emerging body of literature indicating that nocturnal asthma symptoms and poor sleep warrant further attention.
There are some limitations to this study. First, this is a cross-sectional study and we cannot determine causality or directionality from these analyses. Second, while a validated sleep scale was used, quality of sleep was only assessed by parent report and was not confirmed by more objective assessment. Similarly, child and parent sleep quantity were measured at one time point by parent report only. Additionally, this study lacks a healthy control group for comparison, and therefore these results can only be generalized to a similar urban, pediatric population with significant asthma. We purposely selected a group of children with persistent asthma symptoms at the time of screening for this study, yielding a relatively homogenous group. Despite this, the prevalence of nocturnal symptoms among this group is striking. Some sources of unmeasured confounding such as child’s weight status, stress, family history of poor sleep, allergies, seasonal outdoor irritants, and additional indoor irritants, should be considered in future studies. Finally, additional investigation is needed to further explain the relationship between sleep quality and nocturnal asthma, and to assess daytime functioning and academic consequences of nocturnal asthma symptoms and disturbed sleep.
There are several potential implications from this work. Many urban children with asthma are experiencing nocturnal asthma symptoms and sleep disturbances. However, the full burden of nocturnal symptoms on a child and his or her family may not be recognized by primary care providers. This may be a consequence of under-report by parents and lack of systematic screening. Our data suggest that primary care providers should routinely ask about nighttime asthma symptoms and sleep difficulties during their interactions with patients with asthma and emphasize the importance of nighttime symptom control and adequate sleep to caregivers. In addition, many children with asthma receive suboptimal preventive care.33
A full understanding of the level of burden experienced by the child and family is needed to activate all parties in developing an effective treatment plan including guideline-based preventive medications and avoidance of potentially harmful triggers, in particular ETS. Such improvements in care are needed to help alleviate nocturnal asthma symptoms and improve quality of sleep for pediatric patients with asthma, which could have important implications both for the child’s daytime functioning, behavior, school attendance and performance, as well as the parents overall sleep and quality of life.