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Volume 14 No. 03
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Scientific Investigations

Long-Term Impact of Sleep-Disordered Breathing on Quality of Life in Children With Obesity

Sherri L. Katz, MDCM, MSc1; Joanna E. MacLean, MD, PhD2; Nicholas Barrowman, PhD3; Lynda Hoey3; Linda Horwood, MSc4; Glenda N. Bendiak, MD, MSc5; Valerie G. Kirk, MD5; Stasia Hadjiyannakis, MD1; Laurent Legault, MD4; Bethany J. Foster, MD, MSCE4; Evelyn Constantin, MDCM, MSc(Epi)4
1Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, Ontario, Canada; 2Stollery Children's Hospital, University of Alberta, Edmonton, Alberta, Canada; 3Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada; 4Montreal Children's Hospital, McGill University Health Centre, Montreal, Quebec, Canada; 5Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada

ABSTRACT

Study Objectives:

(1) To determine baseline quality of life (QOL) among children with obesity and newly diagnosed moderate-severe sleep-disordered breathing (SDB) and to compare it to the reported QOL of children with obesity or SDB alone and healthy children. (2) To evaluate QOL change after 1 year.

Methods:

A prospective multicenter cohort study was conducted in children (8–16 years) with obesity, prescribed positive airway pressure (PAP) therapy for moderate-severe SDB. Outcomes included parent-proxy and self-report total and subscale scores on the PedsQL questionnaire (baseline and 1-year).

Results:

Total PedsQL scores were indicative of impaired QOL in 69% of cases based on parent-report and in 62% on self-report. Parents reported significantly lower QOL in our cohort than that reported in other studies for children with obesity or SDB alone or healthy children, on total PedsQL score and on social and psychosocial subscales. PedsQL total scores for participants were significantly higher (mean difference 7.3 ± 15.3, P = .03) than those reported by parents. Parents reported significant improvements in total PedsQL (mean change 7.29 ± 13.73, P = .04) and social functioning (mean change 17.65 ± 24.69, P = .04) scores after 1 year. No significant differences were found by children's self-report or by PAP adherence.

Conclusions:

QOL of children with obesity and SDB is lower than in children with obesity or SDB alone or healthy children. One year later, children reported no significant changes in QOL; parents reported significant improvements in total PedsQL and social functioning scores. PAP adherence did not significantly affect QOL change in this population.

Commentary:

A commentary on this article appears in this issue on page 307.

Citation:

Katz SL, MacLean JE, Barrowman N, Hoey L, Horwood L, Bendiak GN, Kirk VG, Hadjiyannakis S, Legault L, Foster BJ, Constantin E. Long-term impact of sleep-disordered breathing on quality of life in children with obesity. J Clin Sleep Med. 2018;14(3):451–458.


BRIEF SUMMARY

Current Knowledge/Study Rationale: Children with obesity and those with sleep-disordered breathing have independently been shown to have impaired quality of life, but quality of life in children with both conditions has not been well studied. The long-term effect on quality of life in this population is unknown.

Study Impact: Parent-reported quality of life in children with obesity and sleep-disordered breathing is significantly worse than prevalence reported for children with either condition alone or healthy children, and although quality of life may improve in some 1 year later, the proportion with impaired QOL is nearly unchanged. Clinicians should be aware that children with both obesity and sleep-disordered breathing may have impaired quality of life that can persist over time.

INTRODUCTION

Sleep-disordered breathing (SDB), caused by repetitive partial or complete airway obstruction or hypoventilation during sleep, can result in desaturation, hypercapnia, and sleep fragmentation.1,2 In children, the most common cause of SDB is obstructive sleep apnea (OSA), which affects 1% to 3% of healthy children and 13% to 66% of children with obesity.3 Given the rising rates of obesity, SDB associated with obesity in children is also increasing.4 SDB causes sequelae including impaired glucose tolerance, hypertension, and reduced neurocognitive function.3 Additionally, it is associated with significant impairments in quality of life (QOL), reported in 60% of children with SDB.3,57 Further, children with obesity have been shown to have lower QOL than their lean peers, even in the absence of SDB, comparable in magnitude to that of children with cancer.8 The presence of both SDB and obesity may therefore compound the reduction in QOL. This association has been demonstrated in adults, in whom work-related QOL was lower in individuals with obesity in the presence of comorbidities including SDB.9 In children with obesity and SDB, there is some evidence of this association8,10; however, in one study8 not all of the study sample underwent polysomnography (PSG) and in the other10 a QOL tool specific for OSA was used that limits comparisons to other populations.

SDB in young children most often manifests as OSA related to adenotonsillar hypertrophy and is often treated with adenotonsillectomy. In children with concurrent obesity, however, adenotonsillectomy may be less effective11,12 because they may not actually have adenotonsillar hypertrophy or because their SDB is more complex, including increased mass around the airway causing closure during sleep, and/or concurrent hypoventilation. They may also have an elevated anesthetic risk.13 When adenotonsillectomy is not a treatment option or is not successful, positive airway pressure (PAP) is usually prescribed.

In adults, the use of continuous PAP (CPAP) for OSA treatment results in improved QOL compared to lifestyle modification alone.14 In children, adenotonsillectomy improves QOL compared to baseline,5,6,1517 although, in some studies, less improvement is seen in children with obesity compared to lean children.18 To our knowledge, there has only been one study of short-term PAP therapy in children, in whom QOL improved after 3 months of treatment.19 Long-term QOL outcomes with PAP therapy have not been reported in children.

The primary objective of this study was therefore to determine the QOL of children with obesity and newly diagnosed SDB and to compare it to reported QOL of healthy children, children with isolated obesity, and children with SDB, as reported in the literature. We hypothesize that QOL in children with obesity and newly diagnosed SDB is lower than that reported in healthy children and lower than that reported in children with obesity or SDB alone. Secondary objectives included evaluation of the change in QOL over time, and comparison of QOL in children adherent and nonadherent to PAP therapy. We hypothesize that QOL in children with obesity and SDB will remain impaired over time but will improve with PAP use.

METHODS

Study Design

This was a prospective multicenter cohort study of children with obesity and newly diagnosed moderate-severe SDB for whom PAP therapy was prescribed. Participants were recruited from four tertiary care pediatric centers across Canada, between June 2011 and July 2014. All children and their parents provided written informed consent, and assent where applicable. The study was approved by the Research Ethics Board at each of the participating study sites (Children's Hospital of Eastern Ontario, Ottawa, Ontario; Montreal Children's Hospital, Montreal, Quebec; Stollery Children's Hospital, University of Alberta, Edmonton, Alberta; Alberta Children's Hospital, Calgary, Alberta). Participants were followed for 1 year, with study evaluations performed at baseline (at the time of recruitment and within 3 months of PAP initiation), 6 months and 12 months. QOL was assessed as a secondary outcome of a larger study, for which the primary outcome was change in insulin resistance after PAP therapy prescription.20

Study Population

The study population, as reported elsewhere,20 included children 8 to 16 years old with obesity, defined as body mass index (BMI) greater than or equal to the 95th percentile for sex and age21 with moderate-severe OSA and/or obesity hypoventilation that was newly diagnosed on PSG, for which PAP therapy (CPAP or bilevel PAP) was prescribed by the treating physician. The presence of SDB was confirmed prior to enrollment in the study, using overnight PSG, conducted and scored according to American Academy of Sleep Medicine recommendations.22,23 Moderate to severe OSA was defined as an obstructive apneahypopnea index (OAHI) of greater than or equal to 5 apnea or hypopnea events per hour. Obesity hypoventilation was defined as CO2 > 50 mmHg for > 25% of total sleep time using the American Academy of Sleep Medicine criteria.24 Although no strict guidelines for defining severity of OSA in children exist, the definition for this study was derived by a consensus of pan-Canadian pediatric sleep medicine experts that this degree of SDB warranted PAP therapy. Eligible children were also required to be fluent in English or French.

Children were excluded from the study if they had comorbid conditions that may contribute to the development of SDB, including craniofacial anomalies other than tonsillar and adenoid enlargement, central nervous system lesions, neuromuscular, neurological, or genetic syndromes, congenital heart disease and/ or diagnosed ventricular dysfunction, or chronic respiratory disease with the exception of asthma. Conditions associated with impairment of insulin resistance, including known type 1 or type 2 diabetes treated with medication and use of oral or intravenous corticosteroids within the past 3 months, were additional exclusion criteria as metabolic outcomes were evaluated in this study. Those already receiving and adherent with PAP therapy and those using pharmacological sleep aids were also excluded.

Measurements

Age, sex, height, and weight were determined at baseline and 12 months. BMI, along with sex- and age-specific z-scores and corresponding percentiles, was calculated.21 Baseline polysomnogram outcomes of interest included the total apnea-hypopnea index (AHI), OAHI, lowest oxygen saturation nadir, highest measured carbon dioxide (transcutaneous or end-tidal), and sleep efficiency. Sleep duration in hours was recorded on self-report diaries.

Adherence for each of the children in the study was determined by established criteria (use of PAP therapy for an average of ≥ 4 h/night and > 50% of nights). Objective machine downloads were used primarily to determine whether the adherence definition for the study was met. In all cases, downloads were available for at least some of the study period. We verified that there were no changes in the adherence pattern during gaps in the downloaded information using adherence judgments from the treating physician.

QOL was assessed using a pediatric QOL scale, the PedsQL (generic version), which was administered separately to children and parents, at baseline and 12 months. The PedsQL is a validated pediatric QOL instrument, previously used to study other populations of children with chronic diseases. It generates a total score as well as subscale scores in the following domains: physical functioning, emotional functioning, social functioning, and psychosocial functioning. A score more than one standard deviation (SD) below the population mean is considered to be a meaningful cutoff point to identify individuals with QOL that is impaired relative to healthy individuals. This cutoff score for impaired QOL corresponds to a score below 69.7 on child scales or below 65.4 on parent-proxy scales.25 Further, a change in score of 4.4 for children, or 4.5 for parent-proxy report of the total scale score constitutes the minimal clinically important difference.25

Statistical Analysis

Characteristics of the cohort at baseline were summarized using median, interquartile range, and range. The total and sub-scale scores on the parent and child/teen PedsQL questionnaire were summarized using mean ± SD. The percentage of scores below the thresholds indicative of impaired QOL was computed for parents and children. Differences between child and parent scores were assessed using paired t tests and intraclass correlation coefficients. The mean of child and parent PedsQL total and subscale scores for the study cohort were compared to those reported in the literature for children with obesity,8 children with OSA,26 and healthy children,27 using Student two-sample t test based on reported and observed SD. Spearman correlations were used to test the associations of the total and subscale scores on the parent and child/teen PedsQL questionnaire with sleep parameters, BMI z-score, and sex. Nonparametric testing (Spearman correlation) was used because the distribution of sleep parameters did not follow a normal distribution.

Changes in PedsQL scores over 1 year for parents and participants were evaluated using t tests. Differences in the percentage of changes exceeding the threshold for minimal clinically important difference were compared between parents and children using McNemar test. When PedsQL subscales were analyzed, adjustments were made for multiple testing using the Holm method.

To evaluate the association between adherence to PAP therapy and change in PedsQL scores, analysis of covariance was used to model PedsQL score at 12 months, with PedsQL score at baseline and adherence as predictors. Change in PedsQL score was also compared between participants who were adherent and nonadherent to PAP.

RESULTS

The study included 26 children of 47 screened. Characteristics of the cohort at baseline are shown in Table 1. Most of the participants were male. All participants were obese as per our study entry criteria and 19 (73%) had BMI above the 99th percentile. Seventeen children (65%) had severe SDB (total AHI > 10 events/h). The median AHI was 14.5 events/h.

Characteristics of the total group (n = 26) at baseline.

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Table 1

Characteristics of the total group (n = 26) at baseline.

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PedsQL total scores for participants were significantly higher (mean difference 7.3 ± 15.3, P = .03) than those reported by parents. This was also the case for social functioning (mean difference 14.4 ± 21.1, P = .003) and psychosocial functioning (mean difference 7.1 ± 15.4, P = .03). Intraclass correlation coefficients were all moderate (ranging from 0.44 to 0.67)28 and statistically significant (P < .01, Table 2).

Baseline PedsQL scores and agreement between parent and child (n = 26).

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Table 2

Baseline PedsQL scores and agreement between parent and child (n = 26).

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Total PedsQL scores were indicative of impaired QOL in 69% of cases based on parent report and in 62% of cases based on self-report. All parent- and self-reported total PedsQL scores and subscale scores of children in our cohort were significantly lower than those of healthy children reported in the literature27 (Table 3). Although child total and subscale scores for this cohort were lower than those of children with obesity or children with OSA reported in the literature,8,15 they were not statistically different. Parents reported that their children had significantly lower scores on all scales compared to children with OSA. Compared to children with obesity, parents of children in our cohort reported significantly lower total scores and decreased social and psychosocial functioning.

Comparison of PedsQL scores in our study population to other study populations in the literature.

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Table 3

Comparison of PedsQL scores in our study population to other study populations in the literature.

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Correlations between PedsQL scores and demographic and sleep parameters were examined at baseline. Age was not significantly associated with PedsQL scores except for self-report of social functioning, which was higher in older children (Table 4). Total PedsQL reported by participants was significantly higher among those with the lowest O2 saturation nadir (Spearman correlation −0.42, P = .03). This was also true on the emotional and psychosocial subscales (Spearman correlation −0.66 and −0.47 respectively, with P = .004 and P = .03). Parents reported higher emotional functioning among those with a higher OAHI (Spearman correlation 0.69, P = .004). No other sleep parameters were significantly associated with PedsQL total or subscale scores.

Spearman correlations at baseline (n = 26).

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Table 4

Spearman correlations at baseline (n = 26).

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Parents reported a clinically and statistically significant improvement in total PedsQL score and social functioning from baseline to 12 months (Table 5). There were no significant changes over time reported by children. Approximately half of parents reported clinically significant improvement in PedsQL scores, whereas approximately one-third of children did, although differences in scores between parents and children did not reach statistical significance. Nevertheless, total PedsQL scores were lower than the normal range in 63% of cases based on parent report and in 62% of cases based on self-report. No statistically significant differences were found between those adherent and nonadherent to PAP therapy (Table 5). In order to assess the effect size of the difference in changes in QOL between adherent and nonadherent participants, Cohen d was calculated. For the total PedsQL reported by parents, the effect size was 0.63.

Change in PedsQL score over 1 year for parents and participants (equal variances not assumed).

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Table 5

Change in PedsQL score over 1 year for parents and participants (equal variances not assumed).

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Change from baseline to 12 months in BMI z-score was not significantly associated with change in total PedsQL score of either participants (Spearman correlation −0.08, P = .72) or parents (Spearman correlation 0.10, P = .70).

DISCUSSION

In this study, all PedsQL total and subscale scores reported by children with OSA and obesity and their caregivers were lower than expected in healthy children, indicative of clinically important impaired QOL. Furthermore, parents reported significantly lower QOL and lower social and psychosocial functioning compared to that of children with either obesity or OSA alone. Parent scores showed significant improvements in overall QOL and social functioning 1 year later, but children's scores did not change, irrespective of PAP adherence. Approximately one-third of children and half of parents reported clinically significant improvement in scores 12 months later, even if the proportion of respondents who continued to have impaired QOL was nearly unchanged.

The finding of impaired QOL in this population with two important health problems (SDB and obesity), each independently associated with QOL impairment, is not surprising and is consistent with other studies.6,8 The degree of impairment in QOL reported in children with obesity is comparable to that of children with cancer.8 QOL is also decreased in children with OSA and is similar to that of children with juvenile rheumatoid arthritis.29 The presence of both conditions in our study was associated with even greater impairment in QOL than either obesity or OSA alone, according to parental reports. This finding was notable in total scores and particularly affected social and psychosocial functioning. Lower QOL has also been reported in adults with both OSA and obesity compared to either condition alone, supporting our finding that the presence of multiple comorbidities is associated with greater impairment of QOL.

Parents reported significant QOL improvements 1 year after prescribed PAP treatment, consistent with those reported in a study of adults with obesity using PAP therapy for SDB and in one pediatric study.8,14 However, children with obesity and SDB do not report improvements in QOL after PAP prescription, consistent with a lack of change seen after adenotonsillectomy in another pediatric study.15 It is possible that the metrics assessed by the PedsQL are not those most valued by children with obesity and SDB when evaluating their QOL and/or that children may not recognize the effect of their clinical conditions on their well-being. It is also possible that the perceived burden of PAP therapy itself has a negative effect on QOL that counterbalances positive changes in QOL associated with SDB improvement., which results in no net improvement of QOL following PAP therapy. Finally, slow gradual improvement in sleep symptoms may make it difficult for children to notice changes from baseline.7

Participants and parents showed moderate agreement in reporting children's QOL; however, it is notable that participants on average reported higher QOL than their parents' assessment in all domains except emotional functioning. This is consistent with Varni's finding of higher QOL reported by children with a multitude of chronic conditions than by their parent-proxy,29 but inconsistent with Garetz's findings in children with OSA in whom parents reported higher emotional functioning scores than children.15 Interestingly, it is the emotional functioning aspects of QOL that have correlated with OSA in other studies, suggesting this domain may be most affected by OSA.7 It is possible that parental concerns about sleep apnea and their child's general health status may affect their perceptions of their child's QOL with this condition,6 which may explain why parents rate their child's QOL lower than that reported by participants.

There were no significant associations between QOL and baseline BMI z-score, sex, Tanner stage, or age. By virtue of our inclusion criteria, our entire cohort had obesity and was relatively homogenous, making it more difficult to demonstrate associations between BMI z-score and QOL. QOL is lower in adult females than males with OSA,9 but sex differences in QOL at baseline were not seen in our study. We also did not show an association between age or pubertal status with QOL. This is similar to findings of another study in which Tanner stage was not associated with QOL.7

In most cases, sleep parameters were not associated with QOL. Although the literature has reported variable associations of QOL or lack thereof with metrics of OSA severity including AHI, our study found that parents of children with higher OAHI reported lower emotional functioning in their child. In addition, we documented an association between a lower oxygen saturation nadir and higher total PedsQL score as well as higher emotional and psychosocial functioning reported by children. This finding is in contrast to a previous pediatric study that showed that lower oxygen saturation nadir was associated with poorer QOL.30 This unanticipated finding that lower oxygen saturation nadir is associated with higher scores on several measures may suggest that those children with more severe disease have experienced greater compensation and adaptation to their health condition, particularly if it has been long-standing.

Despite a lack of statistically significant changes in QOL reported by children after 1 year, one-third reported clinically significant improvement in their scores. Further, parents reported statistically significant improvements in total PedsQL score and social functioning. This finding is interesting and novel, especially because social functioning was particularly impaired in children with both SDB and obesity. Prior studies reported improvements in overall QOL, physical symptoms,10 and daytime sleepiness.31 Certainly, improvements in physical functioning and alertness can in turn influence motivation and desire to interact with others.

There were no significant differences in change in QOL over 1 year between those children adherent and nonadherent to PAP therapy, which may be a reflection of our small sample size and limited power to detect differences between subgroups. For example, the effect size of the changes observed in total PedsQL reported by parents was 0.63. If a new study were conducted where the effect size was unchanged, then assuming equal numbers of adherent and nonadherent participants, a sample size of 41 participants per group would be required to have 80% power to achieve statistical significance at P < .05. It is also possible that PAP does not affect QOL significantly in this population. Further study is required to determine the effect of PAP on QOL in obese youth.

This study has several strengths, including its long-term follow-up of a homogeneous population, gold standard assessments of sleep parameters, and use of a participant- and parent-reported validated pediatric QOL tool. The study sample is representative of the Canadian population of youth with obesity presenting for PSG, as all children at the four participating centers meeting eligibility criteria were approached to participate. The study also has several limitations. First, the PedsQL, although validated and used widely to assess QOL in pediatric populations with obesity and children with OSA, is not specific for either condition and therefore may not detect all values and parameters that affect QOL in the study population. For example, PSG and PedsQL both measure important variables in characterizing OSA, but they measure different metrics that can have important but different effects on daytime function.6 Second, additional covariates that can influence QOL include race and the presence of asthma, which were not assessed in this study.15,32 Third, the sample size of our study was relatively small, limiting power to detect associations, changes over time, and differences between adherent and nonadherent subgroups. Because of the small sample size, we also could not investigate whether PedsQL score at 12 months is affected by an interaction effect between baseline PedsQL score and adherence. Such a model would be appropriate to examine whether patients benefit differently from adherence to PAP according to their baseline PedsQL score. Reporting bias may also be of concern if parents wish to justify the treatment received by their children. Fourth, it is possible that other support or participation in additional activities may have contributed to improvements in QOL. Finally, a less strict definition of adherence was applied in this study relative to others.14 Nonetheless, even with this adherence definition, clinically important changes in QOL were seen; additionally, our adherence pattern with the adherence definition we used may be more consistent with reported PAP adherence patterns.33,34

In conclusion, children with both obesity and QOL have significantly lower parent-reported QOL, and lower social and psychosocial functioning than children with obesity or OSA alone. QOL in these children is low and in a clinically important range, with PedsQL scores comparable to those of children with cancer or juvenile arthritis.29 One year later, parents report significant improvements in total PedsQL score and social functioning, although children do not report significant changes. We hope that these findings will encourage more inquiry by clinicians about QOL and well-being in this population, as well as more proactive intervention in this group at particularly high risk of QOL impairment. Future studies should also consider additional use of disease-specific QOL tools for SDB, which may be more sensitive to detect changes related to treatment. Larger studies are needed to evaluate the effect of PAP adherence on QOL changes over time.

DISCLOSURE STATEMENT

Work for this study was conducted at Children's Hospital of Eastern Ontario, Ottawa, Ontario; Montreal Children's Hospital, Montreal, Quebec; Stollery Children's Hospital, Edmonton, Alberta; Alberta Children's Hospital, Calgary, Alberta. This study was funded by the Canadian Institutes of Health Research. The authors report no conflicts of interest. All authors have seen and approved the manuscript.

ABBREVIATIONS

BMI

body mass index

CO2

carbon dioxide

CPAP

continuous positive airway pressure

OAHI

obstructive apnea-hypopnea index

OSA

obstructive sleep apnea

PAP

positive airway pressure

PSG

polysomnography

SDB

sleep-disordered breathing

SD

standard deviation

QOL

quality of life

ACKNOWLEDGMENTS

The authors thank the research assistants, as well as the children and families, who participated in the study. Author contributions: Drs. Katz and Constantin designed the study, and participated in the data collection, analysis, and manuscript drafting. Dr. Katz wrote the first draft of the manuscript. Drs. MacLean, Bendiak, and Kirk, as well as Ms. Hoey and Ms. Horwood, assisted with study design, data collection, and review of the manuscript. Dr. Barrowman conducted the statistical analysis for the study and advised on the study design. Drs. Hadjiyannakis, Legault, and Foster provided content expertise during study design and contributed to the writing of the final manuscript.

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