Correlation between Severity of Atopic Dermatitis and Sleep Quality in Children and Adults

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by pruritic, dryness and eczematous lesions1. In recent years, many studies have shown higher rates of AD prevalence ranging from 17% in children and 2% to 3% in adults2. The chronic and recurrent nature of AD, combined with the absence of a curative treatment, negatively impact the quality of life (QOL) of the patient. The symptoms of AD can limit a patient's physical and psychosocial development as well as lower their overall QOL, including sleep quality1. Sleep disturbances may have considerable effects on both child and adult patients2, 3 they can result in significant daytime deficits including fatigue, mood disorder, and poor behavioral functioning as well as developmental disorders in children1. Despite the high prevalence of sleep disturbance in AD patients, only a few studies have evaluated the sleep quality in AD patients.

The purpose of this study was to identify the correlation between clinical disease severity, sleep quality and QOL in children and adults with AD. We also analyzed the relationship between disease severity and the components of a sleep questionnaire.

We performed this study to evaluate the relationships between clinical disease severity, QOL and sleep quality in children and adults with AD. Several studies have investigated the association between sleep disorders and dermatologic disease. Mostaghimi9 reported the high prevalence of poor mood and sleep problems in chronic skin disorders, including AD and alopecia areata, using the Current Life Functioning questionnaire, the PSQI score and the Beck depression inventory (BDI-II). Camfferman et al.10 reported that children with eczema have significantly reduced neurocognitive functioning including sleep disturbances. They evaluated sleep problems using the sleep disturbance scale for children (SDSC), a neurocognitive assessment by the Wechsler intelligence scale for children (WISC-IV) and overnight polysomnographic (PSG) data, and showed that children with eczema had worse sleep quality on PSG and significantly reduced neurocognitive performance. These two studies did not investigate the association between sleep quality and AD severity. In our study, we evaluated sleep quality according to AD severity in both children and adults.

A recent study by Yano et al.11 evaluated the sleep quality of Japanese adult AD patients by their PSQI score. In their study, PSQI score was associated with SCORAD score, and two components of the PSQI, sleep quality and sleep latency, were significantly associated with SCORAD and DLQI scores. Our study showed that the total score of the sleep questionnaire was not associated with the severity of AD in adult patients, but the sleep quality and sleep latency components of adult patients were significantly associated with AD severity, similar to the Japanese study. In child AD patients of our study, there were significant associations between the total score of the sleep questionnaire and AD severity, and showed a statistical relationship in the five components of the CSHQ, including bedtime resistance and sleep onset delay, which are similar to the sleep latency component of the PSQI. In addition, we evaluated the sleep quality according to SCORAD score which is separated by objective index and subjective index. In both children and adults, sleep quality and QOL are associated with objective signs and subjective symptom in the SCORAD index.

Koca et al.12 evaluated sleep patterns in lichen simplex chronicus (LSC), which were characterized by repeated rubbing and scratching during sleep. They reported that PSG evaluations of 15 LSC patients revealed a significantly higher percentage of stage 2 non-rapid eye movement (REM) sleep and significantly lower percentage of stages 3 and 4 non-REM sleep. Non-REM sleep consists of 4 stages: stages 1 and 2, "light non-REM" sleep, and stages 3 and 4, "deep non- REM" sleep. The scratching episodes were observed in all stages of non-REM sleep, but were most frequent during stages 1 and 2 non-REM sleep. In the light non-REM sleep, a weak stimulus such as the scratching episodes can easily awake the patient and lead to impairment in deep stages of non-REM sleep.

Itching is considered to be the main factor leading to sleep problems in AD patients. We evaluated the pruritus scores of subjective symptom in the SCORAD index which are showed a significant correlation with sleep quality in both children and adults. And, it showed a stronger association in children (r=0.752) than in adults (r=0.578).

In addition, several factors may be provided for the sleep disorder observed in AD patients. Reuveni et al.13 evaluated to characterize the sleep pattern of children with AD. They reported that there is also abnormal sleep fragmentation in well-controlled AD patients. As well as scratching during the active phase of the disease, the itching sensation during clinical remission, itching habit, learned self-comforting behavior, and asthma can also induce the sleep fragmentation in AD patient.

QOL is generally reported to be reduced in patients with AD14, 15. Holm et al.14 evaluated the QOL in 101 AD patients (66 adults and 35 children) compared with healthy controls and showed that patients with AD had reduced DLQI scores compared to controls (p<0.0001). Sleep disturbance has also been reported to have a major influence on the QOL of AD patients. Chamlin et al.15 reported that poor sleep is a major factor impacting the QOL in about 10% of the children with eczema in their study. Our study also showed a significant correlation between sleep quality and QOL in both children and adults.

In this study, we confirmed the significant association between the severity of AD and sleep disorders in children, and also showed statistical significance between the severity of AD and five components of the sleep questionnaire, including bedtime resistance, sleep onset delay, sleep anxiety, parasomnias and sleep disordered breathing. These sleep disturbances may have a greater effect on children, whose physical and psychosocial development are ongoing. In adults, the total score of the sleep questionnaire was not associated with the severity of AD, but the sleep quality and sleep latency components were significantly associated with the severity of AD. Therefore, sleep problems should not be ignored in adult AD patients. Several limitation of this study should be noted. First, the CSHQ was based on parental reporting that is likely to lead to substantial under- or over-reporting of sleep quality of children. Second, there are many factors, including obesity, affecting the sleep quality in AD patients. We did not evaluate for other factors, except for severity of AD which means the possibility of confounding bias is present. Third, for the objective assessment of sleep quality, the polysomnography should have been performed.

Although sleep problems in AD patients are well recognized, there are few published studies or guidelines concerning the clinical management of sleep disturbances in AD patients. Therefore, adequate guidelines for treating or evaluating AD patients' sleep disorders should be provided. Furthermore, the exact mechanism of sleep disorders in AD patients has not been revealed. Therefore, more neurologic or immunologic studies will be necessary to verify the relationship between sleep disorders and AD.