NEW YORK (Reuters Health) - Obese children who have difficulty breathing while they sleep have excessive daytime sleepiness compared with slimmer children who are also chronic snorers, new research in the journal Pediatrics shows.

The symptoms in heavy children are "strikingly reminiscent of excessive daytime sleepiness patterns in adults with obstructive sleep apnea," Drs. David Gozal and Leila Kheirandish-Gozal of the University of Louisville in Kentucky write. The findings suggest, they add, that obstructive sleep apnea looks different in obese children than it does in normal weight kids, which may have implications both for how the condition is treated and how it ultimately affects organ function.

The researchers previously observed that among children with sleep problems, daytime tiredness seemed to be the main symptom in obese kids, while sleepiness tended to manifest itself as inattention and hyperactivity for normal-weight children.

To investigate their hypothesis that kids with the same level of snoring severity would be more likely to be sleepy during the day if they were obese, they observed 50 healthy 6- to 9-year-old, normal-weight children who were habitual snorers and 50 obese children, also snorers, who had been matched by gender, age and ethnicity.

Children were observed for a full night of sleep in the lab, and then the researchers conducted a multiple sleep latency test, which assessed the degree of sleepiness by measuring the time it took the children to fall asleep during the day. The test involved giving the children a chance to nap for 30 minutes every 2 hours, beginning at 8 a.m. Each child had five nap opportunities.

On average, the obese children took 12.9 minutes to fall asleep, compared with 17.9 minutes for the non-obese children. Twenty-one of the obese kids had sleep latency times of 12 minutes or less, while just 5 of the normal-weight children did. Daytime sleepiness was most strongly associated with how many times a child woke up every hour due to respiratory disturbances.

This suggests, the researchers say, that sleep fragmentation my be more common in obese children and that a lack of oxygen during sleep may play a significant role in triggering the biological response that ultimately leads to increased daytime sleepiness.

While obstructive sleep apnea was more common among the obese children than the slimmer children, obese children without the condition were still more likely to have excessive daytime sleepiness than their slimmer counterparts.

Both obesity and obstructive sleep apnea are disorders related to low-level, system-wide inflammation, the researchers add. So both conditions could act together to further increase the levels of inflammation- and sleepiness-promoting substances in the body, the researchers suggest.

While the mechanism behind the link requires further study, they conclude, for now, children with symptoms of excessive daytime sleepiness who have trouble staying awake should be evaluated for obstructive sleep apnea.

SOURCE: Pediatrics, January 2009.

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