Many people have a fear of flying, but a new study suggests it may not be the aircraft crashing that is the biggest danger.
Falling asleep on a plane after drinking could be deadly, scientists have warned, after finding alcohol, sleep and low cabin pressure combine to create a toxic mix that puts a strain on the heart.
Although passengers often have a few drinks to help them nod off on a long-haul flight, experts say it causes oxygen levels in the blood to drop, forcing the heart to beat faster to compensate.
The higher the alcohol consumption, the greater the effects might be, researchers believe, and say it might be time to consider restricting alcohol on long-haul flights.
Although the elderly and those with heart or lung conditions are likely to be at the greatest risk, effects were seen even in young, healthy people.
‘Avoid drinking alcohol on planes’
Dr Eva-Maria Elmenhorst, of the German Aerospace Centre in Cologne, said: “The oxygen levels that we observed in our study were not dangerous for our participants, otherwise we would have woken them up.”
But she added: “The situation might be different for passengers with pre-existing medical conditions. Their oxygen saturation might be low to begin with and then drop to even lower levels. So medical conditions might exacerbate leading to inflight medical emergencies.
“I would advise people with heart or lung conditions to avoid drinking alcohol on planes.”
Atmospheric pressure decreases with altitude, and it is known that the oxygen saturation falls to around 90 per cent in passengers at aircraft cruising height.
It is also known that altitude sickness often occurs after sleep, and that alcohol can further decrease oxygen saturation and cause the heart to beat faster, so researchers wanted to study the impact of all three combined.
In the new study, 48 people aged between 18 and 40 were asked either to sleep in a laboratory or an altitude chamber that mimicked cabin pressure at 8,000 feet.
Twelve participants in each group drank the equivalent of two cans of beer or two glasses of wine, and their sleep cycle, heart rate and blood oxygen levels were measured.
After a two-day recovery period, the test was reversed and carried out for a second time with the participants in the lab asked to sleep in the chamber and vice versa.
People in the sleep lab who had not drunk alcohol had oxygen saturation levels of around 96 per cent, and a heart rate of 64 beats per minute.
However, drinkers in the simulated cabin pressure chamber had oxygen saturation levels of around 85 per cent and heart rate of 88 beats per minute.
Those who slept in the chamber but did not drink had oxygen levels of 88 per cent and a heart rate of 73 beats per minute, showing alcohol had a significant impact above altitude effects.
Usually, at high altitude, receptors in the brain sense the lack of oxygen to make breathing deeper and more frequent to compensate, but sleep and alcohol appear to disrupt the mechanism.
‘Underestimated health risk’
Participants in the experiment slept horizontally on a bed, and researchers are concerned that an economy upright position could make the problem worse, as could frequent flying.
Writing in the journal Thorax, the researchers warned that the consumption of alcohol on board flights is ‘an underestimated health risk which could be easily avoided’ and said that passengers and crew should be informed about the danger.
“It may be beneficial to consider altering regulations to restrict the access to alcoholic beverages on board aeroplanes,” they concluded.
Dr Elmenhorst added: “We found that sleep aggravates the drop in oxygen saturation. We also expected that alcohol, that is frequently consumed inflight, might act synergistically and decrease the oxygen saturation even more.
“We do not know whether the repeated exposure e.g. of frequent travellers might increase their health risk in the long run.”
The study found that oxygen levels fell below the healthy clinical norm (90 per cent) in the high altitude drinkers for more than three hours, with deep sleep reduced to just 46 minutes.
Commenting on the research Professor James Leiper, Associate Medical Director at the British Heart Foundation, said: “There’s already a wealth of evidence showing that alcohol is bad for your heart.
“This small study suggests that there might be an additional impact during long-haul travel.
“More research will be required to fully understand the longer-term health impacts of drinking alcohol while flying.”
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