Sleep apnea — a potentially serious disorder in which breathing repeatedly stops and starts during sleep — affects more than 80% of children with Prader-Willi syndrome (PWS), according to the results of a Chinese study.
Central sleep apnea or CSA, a type of the sleep disorder that’s due to impaired communication between the brain and the muscles that control breathing, was more prevalent in infants with PWS younger than age 2, the researchers found.
The study, “Sleep-disordered breathing and genetic findings in children with Prader-Willi syndrome in China,” was published in the journal Annals of Translational Medicine.
Sleep-disordered breathing (SDB) is common among individuals diagnosed with PWS. It includes hypersomnolence, or excessive daytime sleepiness, CSA, and OSA, or obstructive sleep apnea, which occurs when the airflow is blocked during sleep.
To learn whether such SDBs were linked with the genetic defects that cause Prader-Willi, researchers at the Children’s Hospital of Fudan University, in China, now assessed the prevalence of sleeping disorders in children with PWS. The team also assessed the link between sleeping disorders and demographics, including body weight, and lab tests.
In total, they analyzed data from 48 children with a median age of 16.8 months (range, 3 months to 15.7 years) with a genetically confirmed PWS diagnosis. The children were separated into two groups: infants, age 2 or younger, and children over 2 years. The infant group included 32 babies with a median age of 9.1 months, while the older group was comprised of 16 participants, with a median age of 6.
Most participants (77%) had a paternal chromosome 15q11-13 deletion, the most common cause of PWS. Meanwhile, 11 children (23%) had maternal uniparental disomy (UPD), which means that they inherited two maternal copies of this chromosome 15 instead of one from each biological parent.
A larger proportion of participants in the older group were obese or overweight (15 of 16), compared to only four of the 32 infants. Obesity and overweight were defined according to the body mass index (BMI) z-score — a standard measure of relative weight adjusted for the child’s age and sex.
Older children had significant higher levels of insulin-like growth factor 1 (IGF-1) in the blood than infants — 126.7 vs. 31.5 nanograms (ng)/mL. Also, high levels of free-thyroxine 4 (FT4) and thyroxine (T4), two parameters that assess the function of the thyroid gland, were registered in older patients compared with infants — 0.9 ng/mL vs 0.7 for FT4 and 9.0 ng/mL vs. 7.5 ng/mL for T4.
The analysis revealed a significant correlation between age and BMI z-score, as well as between age and the levels of IGF-4, T4, and FT4. The BMI z-score also correlated with these blood test parameters.
Next, the researchers conducted a polysomnography (PSG), or a sleep study — a test used to evaluate nighttime sleep and diagnose sleep conditions. PSG measures brain waves, oxygen level in the blood (percutaneous oxygen saturation, SpO2), heart and breathing rate, and also eye and leg movements.
SDB was common both in children and infants, with 42 participants (87.5%) overall having sleep apnea. Sleep disorders included 11 patients with OSA, 27 patients with CSA, and four participants with both conditions.
Compared with older children, infants were significantly more likely to have CSA (23 vs. four participants), but less likely to have OSA (zero vs. nine).
In addition, the median lowest SpO2 was significantly reduced in children (79%) compared with infants (84%).
The researchers found no significant differences in the prevalence of sleeping disorders between participants with the paternal chromosome deletion and mUPD.
In conclusion, “the prevalence of SDB was high in PWS patients, and central sleep apnea was found to be prevalent in infants with PWS, suggesting that PSG should be performed early to screen for SDB in PWS,” the researchers wrote.
“The association of central sleep apnea and level of FT4 and T4 in infants should be explored further,” they concluded.
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