Sleep Apnea Causes Brain Changes In Children

September 20, 2006 -- Sleep apnea is a fairly common disorder which involves repeated interruptions in breathing, resulting in minor arousals, during the night. In obstructive sleep apnea, the most common, there is a physical obstruction to the airway which interferes with breathing. Sufferers snore loudly and wake up gasping for breath. The repeated arousals during the night result in excessive sleepiness during the day, which in turn can lead to an increase in accidents.

With up to 30 million Americans estimated to be struggling with sleep apnea, major research publications in this space can garner a lot of attention. That was the case recently when a group of scientists from Johns Hopkins (Halbower et al.) announced that not only can obstructive sleep apnea affect childrens' learning and memory, but that left untreated, may result in fundamental changes to the brain.

While this was widely reported in the mainstream media, the implications of this finding for the Chiari community are even more significant. As has been reported previously by this publication, research has shown that a high percentage of Chiari patients suffer from sleep apnea. In fact studies involving formal sleep testing indicate that as many as 50%-75% of Chiari patients may fit into this category.

The percentage is so high, scientists believe, because in many Chiari patients the muscles of the throat and larynx are weak, and during sleep can actually block the airway. Another possibility is that the herniated cerebellar tonsils place pressure on the sleep center located in the brainstem. No matter the underlying mechanism, and even though it is a secondary condition, it is important for Chiari patients (or parents) to understand the significant impact which continued sleep apnea can have.

A growing body of evidence is beginning to show that sleep apnea can result in cognitive impairments in adults (plus an increased risk of car accidents) and memory, learning, and school performance issues in children. In order to study the effects of apnea on children in more detail, and to determine if the repeated interruptions in oxygen result in physical changes in the brain, the Johns Hopkins team used polysomnography (sleep testing), neuropsychological testing, and advanced imaging to compare a group of children with moderate to severe obstructive apnea to a group of healthy children. Their results were recently posted on the website of PLoS Medicine, a free, open-access journal.

For their study, the researchers recruited 19 children, ages 6-16, with confirmed obstructive sleep apnea. They then recruited a control group of 12 healthy children such that the groups were similar in age, gender, ethnicity, and socio-economic status. Children with IQ's below 75, with neurological problems, or who did not speak English were excluded. All the children, from both groups, underwent formal sleep testing, neuropsychological evaluations, and MRI spectroscopy.

The neuropsychological tests were designed to measure overall IQ, executive functioning, memory, motor speed, and visual-spatial perception. MRI spectroscopy is an advanced imaging technique based on MRI technology which can measure the levels of specific substances, known as metabolites, in the brain. Metabolites are the by-products of the brain's normal metabolism and functioning, and abnormal levels are indicative of disease or neuron damage.

The results of the sleep testing were as expected given the design of the study (see Table 1). Namely, that all the children in the apnea group suffered from moderate to severe apnea, whereas none of the healthy children did. However, it was also noted that the average Body Mass Index (BMI) of the apnea group was significantly larger than the control group. BMI is derived from a person's height and weight and is a simple measure of obesity.

The neuropsychological testing revealed that there were significant differences between the two groups in overall IQ, verbal fluency, and working memory. Specifically, the average IQ of the apnea group was a full 15 points below their healthy counterparts. Interestingly, some of the cognitive differences which are found in adults with apnea were not found in this group of children.

The results from the imaging were even more startling, with the apnea children showing abnormal levels of certain metabolites in the frontal cortex and the hippocampus. The frontal cortex, located in the front of the brain, is believed to control high order functions such as planning and reasoning. The hippocampus, located deeper in the brain, is thought to play a critical role in learning and memory. Interestingly, the researchers thought they might find a difference in the cerebellum as well, but they did not.

While the implications of this are striking, namely that apnea may cause structural changes in the brain, it is important to keep in mind that the children in this study all suffered from fairly severe apnea and tended to have high BMI's, which is another health risk factor. Similarly, although the abnormal metabolite findings are similar to what is seen in diseases that affect the brain, the true impact of these chemical changes is not fully understood. Finally, it can not be determined from this study whether the changes seen in the brain are reversible with treatment for the apnea.

However, given the critical nature that these brain structures play, especially during development as a child, it is important to be aware of, and understand, the potential implications of untreated sleep apnea. And with apnea so common in the Chiari community, we should all be thinking about whether that fatigue during the day may in fact be due to problems breathing at night.

Table 1
Sleep Testing Results, Apnea vs Controls (Average Scores)

Apnea (19) Control (12)
BMI 27.9 19.7
Apnea Index 34.6 0.2
Arousal Index 15.7 5.0

Table 2
Significant Differences In Neuropsych Testing Between Apnea and Control Groups

Apnea (19) Control (12)
IQ 85.8 101.1
Verbal Fluency 9.7 12.0
Working Memory 8.3 15.5

Note: The above differences were statistically significant, meaning the difference is unlikely to be due to chance


Related C&S News Articles:

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Strong Link Between Chiari And Sleep Apnea

It Can Be Hard To Get A Good Night's Sleep With Chiari