student research day - Case Western Reserve University School of ...

Matthew Soden
Prevalence and Predictors of Obstructive Sleep Apnea in Children with Sickle Cell Anemia
Matthew Soden, Carol Rosen, MD
Department of Pediatrics - Rainbow Babies and Children Hospital
Prevalence and Predictors of Obstructive Sleep Apnea in Children with Sickle Cell Anemia
INTRODUCTION
Obstructive sleep apnea (OSA) is a common childhood condition (prevalence 2-3%) that can play a causal role in vasoocclusive
and other adverse health outcomes like pulmonary hypertension and central nervous system (CNS) events in
children with sickle cell anemia (SCA). There is a paucity of data about the prevalence of OSA in children with SCA. The
specific aims of this study were to determine the prevalence and predictors of OSA in children with SCA who underwent
overnight full channel polysomnography (PSG) as part of their participation in the multi-site observational cohort Sickle
Asthma Cohort (SAC) study. Most of the studies linking nocturnal respiratory dysfunction to adverse outcomes in
children with SCA have recorded only nocturnal oxyhemoglobin saturation without other measures of sleep, breathing or
upper airway obstruction. It is unknown whether screening recommendations for OSA (ascertainment of symptoms such
as snoring, observed apnea, restless sleep, or daytime sleepiness) in otherwise healthy children would be useful for
children with a chronic condition like SCA. Since OSA in adults is clearly linked to hypertension, other adverse
cardiovascular and CNS outcomes, and daytime dysfunction, it is possible that early detection and treatment of OSA in
this vulnerable pediatric population may improve their health outcomes.
QUESTION: What is the prevalence of OSA in children with sickle cell anemia?
METHODS
A multicenter, prospective cohort study of asthma and adverse health outcomes (pain crises and acute chest syndrome)
in children who were either homozygous for sickle hemoglobin or had sickle beta thalassemia 0 between the ages of 4 to
18 years were identified at three tertiary academic hematology-based care centers (London, Cleveland and St. Louis) and
enrolled into the SAC study. SAC is an ongoing National Heart Lung Blood Institute-funded prospective, observational
cohort study designed to evaluate the contribution of asthma and sleep abnormalities to SCA-related morbidity. This first
report on prevalence includes the first 150 participants recruited into the study who underwent overnight
polysomnography from the start of study in June 2006 through February 1, 2008. All sites in the study used identical
sleep acquisition systems (Embla N-7000, Broomfield, CO), sensors, data collection procedures and followed current
professional standards for overnight collection of sleep and breathing data in children except that carbon dioxide was not
measured. Full channel overnight PSG was performed over a single recording night with studies starting at the child’s
usual bedtime and ending at the child’s spontaneous waking or as late as 7:00 AM. Obstructive sleep apnea indices from
PSG data were used to define OSA. The presence and severity of OSA was measured by the obstructive sleep apnea
index (OAHI3), that is, the number of obstructive apnea events plus the number of hypopnea (reduced breaths)
associated with a 3% desaturation per hour. Because SCA is a chronic condition that can be associated with pre-existing
oxygen desaturation or lower respiratory tract disease, the prevalence of OSA in children with SCA was evaluated using
two threshold definitions: 1) OAHI3 ≥ 2 and 2) OAHI3 ≥ 5. The first definition is commonly used in clinical practice to
diagnose OSA in otherwise healthy children. Definition 2 is similar, but has a more conservative threshold for hypopneas
and was previously used by our group in a large community based epidemiological study of the prevalence of OSA in
school-aged children. Data from standardized questionnaires regarding sleep habits, physiological and anthropometric
measures (height, weight and blood pressure), and other laboratory tests (lung function, blood count) were used to
examine the relationship between OSA and other risk factors or clinical findings.
RESULTS
Of the 149/150 children with successful overnight studies, we excluded 24 studies with lower quality airflow data which
affected the reliability of the OAHI3 measure and 3 studies because the participant was on supplemental oxygen at the
time of the study which limited detection of desaturation related events. The final analytic sample was based on 122
participants.
OSA was present 26/122 (21.3%) of the children with SCA using definition 1 and 13/122 (10.6%) using definition 2.
Results related to the relationships between OSA and other key covariates and potential predictors in children with SCA
were not available at the time of this analysis.
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