Smokers with sleep apnoea reach ‘dangerously low’ oxygen levels

Smokers who suffer from sleep apnoea spend longer than non-smokers at ‘dangerously low’ oxygen levels during their sleep, increasing their risk of cardiovascular death.

Heart Research Institute lead researcher John O'Sullivan.

Smokers who suffer from sleep apnoea experience “dangerously low” oxygen levels which could increase their risk of cardiovascular death.

Sleep apnoea, which occurs when a person’s throat and upper airway become partly or completely blocked, affects as many as one in four people.

Research published in the­ journal ESC Heart Failure has found that those with high levels of nicotine within their blood spend an average of two minutes 18 seconds longer than a non-smoker at an oxygen saturation level below 90 per cent.

Lead researcher John O’Sullivan, from the Heart Research Institute, said the discovery provided a definitive answer to years of speculation of links between sleep apnoea and smoking.

“We know smoking is bad for the heart … and ­although smoking is known to increase risk of sleep apnoea, the interaction of smoking with sleep apnoea has not been quantified,” he said.

“We were able to find a linear correlation between the levels of the metabolite cotinine, a molecule formed once nicotine enters the body, and the degree to which blood oxygen levels reduce during sleep.

“The more cigarettes you smoke, the higher levels of cotinine you’ll have.”

The findings were particularly important given that sleep apnoea is estimated to affect a billion people globally, Dr O’Sullivan said, adding that normal oxygen saturation levels while a person is asleep are between 95 and 100 per cent.

“People who spend more time with an oxygen saturation less than 90 per cent end up with more cardiovascular death than people who don’t,” he said.