In a new study, Pennsylvania researchers found that kids with insomnia and shorter sleep duration had impaired modulation of heart rhythm during sleep.
The new research showed that insomnia symptoms were consistently associated with impaired heart variability measures.
The researchers also found a significant but less consistent pattern with shortened sleep duration and decreased heart rate variability.
Heart rate variability is the beat-to-beat variations of heart rate. In a healthy person, beat-to-beat intervals change slightly in response to automatic functions like breathing.
The study included 612 elementary school children in the first to fifth grades. The children were average age 9, and 25 percent were non-white and 49 percent were boys. All were generally in good health. Their parents completed the Paediatric Behaviour Scale, including two questions that focused on symptoms of insomnia.
Researchers examined the children overnight in a sleep laboratory with polysomnography (PSG), a standardized method for measuring sleep disorders. The researchers measured sleep duration, trouble falling asleep, the number of wake-ups and problems going back to sleep if awakened.
They also measured cardiac autonomic modulation (CAM), the balance of the sympathetic and the parasympathetic control of the heart rate rhythm.
"Kids who sleep a longer duration have a healthier heart regulation profile compared to kids who sleep shorter durations," said Duanping Liao, co-author of the study and professor of epidemiology at Penn State University College of Medicine in Hershey, Pa.
"Their hearts are more excitable if they have insomnia. If the heart is too excited, that means it is beating too fast and usually that isn't good. These data indicate that among young children with insomnia symptoms reported by their parents, there already is an impairment of cardiovascular autonomic regulation, long before they reach the traditional high-risk period for cardiovascular disease," Liao added.
The study has been reported at the American Heart Association's 50th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.