Sleep apnoea and cardiovascular disease
by Maryke Steffens
Some research suggests there are links between sleep apnoea and cardiovascular disease. But does every severe snorer need treatment?
Published 23/07/2009 http://abc.gov.au/health/thepulse/stories/2009/07/23/2633402.htm
We all know that eating too many cheeseburgers, never exercising and smoking can all contribute to cardiovascular disease, but what about
Most of us consider snoring as little more than an annoyance. But there is some suggestion that an extreme form of snoring, known as obstructive sleep apnoea (OSA), can put you at increased risk of certain life-threatening cardiovascular conditions.
OSA is a condition where the muscles in your throat and upper airway collapse repeatedly while you sleep, preventing you from breathing and partially rousing you from sleep many times during the night. It affects roughly 25 per cent of men and 10 per cent of women over the age of 30, although it's more common in those over 65.
In the past, you were only treated for sleep apnoea if you felt excessively sleepy during the day, but we now know that OSA doesn't just fragment your sleep. These prolonged pauses in breathing can cause your blood oxygen levels to fall and your heart rate and blood pressure to rise. It's been theorised that this may put you at increased risk of more life-threatening cardiovascular conditions such as hypertension (high blood pressure), atherosclerosis (clogging and hardening of the arteries), heart failure and stroke.
So if you have obstructive sleep apnoea, but don't feel sleepy during the day, should you seek treatment?
What causes sleep apnoea?
First, it's important to know whether you have OSA or not. The disorder is caused by a number of factors, says Ron Grunstein, a professor of sleep medicine at the Woolcock Institute of Medical Research in Sydney, including the shape of your face.
"If you have a flatter or rounder face, you're more likely to have sleep apnoea. If you have a receding jawline, you're more likely to have sleep apnoea," he says.
These facial structures tend to narrow the upper airway and can also cause you to snore. If you are overweight, you are also more likely to have sleep apnoea as the fat around your throat puts pressure on your upper airway.
OSA is usually diagnosed using clinical tests and a sleep study, where your brain activity, breathing and blood oxygen levels are measured overnight by a technician in a lab.
Many people pause during breathing while they sleep, but if the study finds that these interruptions (apnoeas) are longer than normal, that is from 10 seconds up to as long as a minute, and occur five or more times an hour, then you may have a mild form of OSA. Moderate OSA is defined as between 15 and 30 apnoeas per hour, and severe OSA as more than 30 apnoeas per hour.
Is there a link with cardiovascular disease?
Because obstructive sleep apnoea appears to put the cardiovascular system under stress, various research groups have looked into the association with cardiovascular disease.
A medium-sized observational study found that people with untreated, severe OSA have more heart attacks and strokes than people of the same age, weight and gender who don't have sleep apnoea. Another small study looking at people with coronary artery disease found that those who also have OSA were more likely to die from their heart disease within five years than those who don't have OSA.
The problem with these studies, says Grunstein, is that many people with sleep apnoea are also overweight or obese, and it's difficult to tell whether their cardiovascular health problems are due to their weight, or whether their sleep apnoea is contributing as well.
One way to get stronger evidence is to compare people who receive treatment for their sleep apnoea with those who don't. Sleep apnoea is usually treated by CPAP (continuous positive airway pressure) a mask attached to a machine that keeps your airway open by forcing air through the nose and mouth.
Several small- to medium-sized observational studies seem to suggest that treatment (primarily with CPAP) reduces your cardiovascular risk. But before you book yourself in to get a CPAP machine, remember that we still don't have definitive evidence the type provided by large randomised controlled trials. A large trial of 5000 people (including Australians) is ongoing at the moment, but it's not due to finish for several years.
Should you seek treatment?
If your sleep apnoea is severe and you also have other risk factors for cardiovascular disease for example you are overweight, have high blood pressure or high cholesterol Grunstein recommends that you consult your doctor. If a sleep study finds that you have large drops in your blood oxygen levels during sleep, your doctor may well recommend treatment with CPAP. "We think that the links between severe lack of oxygen and the risk of [cardiovascular] disease, especially in people who are already at risk, is probably unacceptable, and we need to treat those people," says Grunstein.
However, if your partner says you snore a bit, but you're not sleepy and otherwise feel fine, then you probably don't need to be overly worried about seeking treatment, says Grunstein. Just because you have sleep apnoea doesn't mean it's impairing your health, he says, and the treatments like CPAP, or alternatives such as surgery or wearing a mouthguard, can be unappealing or uncomfortable to use.
What you can do is ramp up your exercise and eat healthily to lose any excess weight. Studies have shown that this can decrease the severity of your sleep apnoea. If you take this path, not only will your heart thank you, your partner and possibly the neighbours may too.