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Down Syndrome Abstract
of the Month: June 1999

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Sleep characteristics in children with Down syndrome.

Levanon A, Tarasiuk A, Tal A
J Pediatr 1999 Jun;134(6):755-760

Sleep Wake Disorders Unit, Department of Physiology, and Department of Pediatrics and Pediatric Pulmonary Unit, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.

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Background: -- Obstructive sleep apnea syndrome is common in children with Down syndrome (DS). Little is known about sleep patterns, especially arousals, awakenings, and movements during sleep in children with DS.
Objective: -- To determine the characteristics of sleep disorders in children with DS and to define the associations between respiratory disturbance and arousals, awakenings, and movements.
Methods: -- The study included 23 children with DS, compared with 13 children with primary snoring. All underwent a 6- to 8-hour sleep study.
Results: -- The respiratory disturbance index was significantly higher in the children with DS. Sleep was significantly fragmented in children with DS, who had a significantly higher arousal/awakening (A/Aw) index (24.6 7.9 events/h) compared with the comparison group (17.6 4.0 events/h). A higher percentage of jerks associated with A/Aw and respiratory event-associated A/Aw was observed in patients with DS (45.2% 25% and 8.6% 6.4%, respectively) compared with the control patients (10.2% 4.5% and 1.5% 2.1%). The median length of occurrences of stage 2 sleep was 27% shorter in the DS group. The number of shifts from "deeper" to "lighter" stages of non-rapid eye movement sleep was 30% greater in the DS group.
CONCLUSION: -- Children with DS have significant sleep fragmentation, manifested by frequent awakenings and arousals, which are only partially related to obstructive sleep apnea syndrome.

My comments:

This is chock full of interesting facts. Let me try this in plain English.

23 children with DS, aged 1 to 10 years of age, were studied. 13 were children who had been referred to the Sleep Clinic due to concerns about difficulty in breathing while asleep; the other 10 had no such difficulties.

There were no differences between the children with DS or the control children in "sleep efficiency," which was defined as the ratio of total sleep time to time in bed. This averaged about 87% for both groups. (87% of the time spent in bed was actually time spent sleeping.)

Of the time spent sleeping, the percentage spent in REM/non-REM sleep was the same for both groups.

The children with DS showed significantly more arousals or awakenings than the control children. This is referred to as "fragmented sleep." These arousals tended to be associated with leg jerks, abrupt changes in body positions and awkward sleeping positions, such as resting the feet against the wall or sleeping in a sitting up position.

When non-REM sleep is divided into 4 stages (I = "light," IV = "deep"), the children with DS spent the same amount of time in each stage as the control children; however, the children with DS had more frequent but shorter periods of time in stage II, meaning this stage was highly fragmented in their sleep.

Nasal and mouth breathing was assessed, as well as oxygen saturation. A "respiratory disturbance index" was calculated based on the number of apneic (no breath for 10 seconds or more or a drop of oxygen saturation of 3% or more) and hypoapneic (reduction of airflow of 50% or more associated with an arousal or drop in oxygen sat.) episodes per hour. The respiratory disturbance index was higher for children with DS than for the control children. The average oxygen saturation for the children with DS during sleep was 94.0%, with the control group having 96.6%.

The respiratory disturbance index was higher for children with DS with symptoms of obstructive sleep apnea (OSA) than for children with DS without symptoms of OSA.

The main point here, though, is that all the children with DS had much more fragmented sleep than the control children, whether they had symptoms of OSA or not, indicating that children with DS have a lower "arousal threshold" than children in general. This lower threshold could be due to some respiratory problem that can't be picked up by a sleep study, or it could be a result of a neurologic abnormality. Reflux, seizures, and the side effects of drugs may also be causes.

In adults, sleep fragmentation may result in impaired daytime alertness, impairment of daily activities, irritability and mood changes. It's not a long jump to consider that fragmented sleep in children with DS may result in behavioral problems as well.
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