“Sleep apnea is when you’re sleeping and your airways collapse, causing difficulty breathing,” says Professor Imbeault. People affected by sleep apnea may think they’re asleep, but their nervous system stays on high alert because of the lack of oxygen in their bodies. This severely reduces the quality of their sleep. People with obesity are at an especially high risk of sleep apnea because the build-up of adipose tissue (or fat) can put pressure on airways.
Your brain and heart under pressure
“Normally, we take around 12 breaths per minute to ensure we can maintain a good oxygen supply and expel the CO2 we produce,” explains Imbeault. However, people with sleep apnea stop breathing several times or take fewer breaths in their sleep. “It’s a bit like if you asked someone to hold their breath for several minutes, until they absolutely needed to start breathing again,” he says.
Lack of oxygen causes the affected individuals to wake up briefly — so briefly they may not even realize they’ve woken up. According to Imbeault, this puts a great deal of stress on our bodies, especially the brain given that one of the roles it plays is to ensure we have a steady oxygen supply.
The heart is affected as well: to compensate for the lack of oxygen, it beats faster, increasing blood flow. Normally, your heart rate drops when you’re asleep, but for people with sleep apnea, “it’s like they’re up and walking all night; there’s a huge strain on the heart to make up for the lack of blood oxygen,” Imbeault explains.
He notes that people affected by sleep apnea are at greater risk of heart disease — and two to three times more likely to die of it. Imbeault and his team have also found in their recent work that sleep apnea affects the body’s ability to manage blood lipid levels, i.e., fats circulating in the bloodstream.
A unique laboratory to study the effects of sleep apnea
It would be quite the challenge to conduct blood tests on sleep apnea patients while they’re asleep, so the research team had to find other ways of simulating this disorder. Before the new Faculty of Health Sciences building opened, study participants would wear a mask that reduced their oxygen intake to simulate a drop in blood oxygen levels (hypoxia).
Those days are over: now, researchers can monitor participants in a hypoxic chamber at the new building. In this chamber, the proportion of oxygen in the air participants breathe drops from 20.93% to 12% or 13%. Participants stay in the chamber for seven hours. During that time, the researchers give them food and take blood samples to show that when the body is experiencing hypoxia, it can’t manage blood lipid levels as effectively.
In other words, “lipids stay in our blood for longer than they should, which can be a problem because they’ll end up sticking to the walls of our blood vessels like grime on a window, forming plaque build-up and increasing the risk of heart disease.” Imbeault is proud that his research team was one of the first to show this happening in humans. Previously, it had only been demonstrated in rats.
How does it feel to be in the hypoxic chamber? Participants may experience nausea or even symptoms similar to drunkenness. “It’s a bit like if you were asked to go hiking at a high altitude, but instead of getting to adapt gradually to it, your body was all of a sudden put into very extreme conditions,” says Imbeault. The brain fights back against the lack of oxygen in the body, he adds, which affects participants’ “ability to move and analyze their environment.”
In the end, sleep apnea doesn’t just rob us of sleep: it’s also hard on our bodies. Thanks to Professor Imbeault’s innovative research, we now have a clearer picture of how this disorder works, bringing us one step closer to finding treatments that could bring a better night’s sleep to thousands.