Sleep is one of life's greatest pleasures. In fact, many people will pay money to be able to enjoy more hours of sleep. Many, undoubtedly, but I assure you, not all of them. Whether sleep apnea is a disease you're already familiar with or a new concept, the truth is that for those who suffer from it, sleep isn't as enjoyable as it could be for the rest of us.
Patients with sleep apnea experience cessation of breathing during the night. When the brain detects these pauses, it momentarily activates to alert you that something is wrong.
Without the patient being fully awake, breathing is restored, but sleep cycles are reset, resulting in abnormal, non-restorative sleep. As a result, sufferers tend to wake up with a headache and feel sleepy for the rest of the day. Ultimately, sleep is not a dream for them.
Sleep apnea in children
Although she said she's probably heard of the condition before, one thing many people don't know is that sleep apnea also affects one in 20 children. This lack of knowledge means that the disease in childhood is underdiagnosed. As a result, many children may suffer from it, but neither they nor their parents know about it.
Sleep during childhood is a key factor in development. Therefore, it should not be surprising that this disease can affect growth and lead to learning problems in children who suffer from it.
For this reason, early detection is a goal often sought by researchers, in an attempt to avoid developing consequences that could burden children for the rest of their lives.
The test approved to diagnose sleep apnea is known as polysomnography. During this test, the child must spend a night in the hospital. At the same time, a wide range of vital medical signals, such as the electrocardiogram, are recorded. These signs are then evaluated by specialists to confirm the presence (or absence) of the disease.
Recording the mentioned signals involves the use of numerous sensors and wires attached to the body, which makes the test especially disturbing for children. This, combined with sleep-outs, costs and long waiting lists, means there is increasing interest in finding an alternative diagnostic test.
Biomedical signals
From the Biomedical Engineering Group at the University of Valladolid, we have been working for some time to study disease using a small number of biomedical signals. Measuring blood oxygen saturation or airflow during sleep has given very good results. We have recently made great progress through ECG analysis alone.
While we sleep, our bodies are controlled by the autonomic nervous system, something similar to running on autopilot. This system is responsible for controlling the body's performance during sleep, ensuring that the heart adapts to a possible lack of oxygen. Thus, when breathing is interrupted, the heart slows down, and then accelerates when normal breathing is restored.
Until recently, sleep apnea studies that looked at this variation in heartbeats focused on frequency bands that focused on patterns of normal autonomic nervous system behavior. However, we knew that the heart generates a distinct pattern in response to disease. In other words, sleep apnea leaves an imprint on the heart's signal during the night.
We then wondered if we could find some frequency bands dedicated to studying these changes due to sleep apnea. By comparing heart rate variability in children with the disease and healthy children, we got the answer. In a recent study, we discovered that there are three specific frequency bands for sleep apnea in children.
Heart rate variability
The discovery of new frequency bands led us to another experiment. In this we obtained the heart signal of 404 children aged between five and ten years suffering from sleep apnea. These children were treated and their heart activity was measured again after seven months. We then decided to evaluate differences between the time before treatment and the months following.
The results of the study allowed us to establish a causal relationship between the recovery of the disease and changes that occurred in one of our frequency bands. This band, called BW2, has been linked to frequent stopping of breathing throughout the night. We also observed differences in BW2 activity between recovered and non-recovered children.
Early treatment
These results are promising and allow us to identify changes in BW2 activity as a potential biomarker for disease recovery. In addition, we only need to record cardiac activity, which we achieve using very few electrodes. Simpler diagnosis and early treatment means healthier children.
Although everything seems to indicate that we are on the right track, there is still a lot of work ahead of us. However, with this research, we are one step closer to accelerating the detection of apnea in children. With this, we hope to finally make sleep a dream for all children.
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