Mixing your long plane ride with alcohol could be a dangerous cocktail for your heart, new research out Monday suggests. The small trial found that healthy volunteers experienced a greater drop in their blood oxygen level and corresponding rise in heart rate after drinking alcohol while sleeping in high-altitude conditions than they did without having a drink. The mix could be much more risky to people already vulnerable to cardiovascular problems or the elderly, the study authors say.
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It’s already known that long-haul flights (usually any flight longer than six hours) can take a minor toll on the body. The high-altitude environment exposes us to lower atmospheric pressure, which can then reduce the level of oxygen saturation in our blood, especially when we’re sleeping. To compensate for this loss, the heart has to work harder, leading to an increased heart rate.
The research was led by scientists at the German Aerospace Center’s Institute of Aerospace Medicine. They knew of past studies showing that drinking alcohol before bed can also decrease blood oxygen saturation and increase heart rate while sleeping. So they wanted to know if a combination of alcohol and long-haul flying would make the problem even worse.
The team recruited healthy volunteers between the ages 18 to 40 for their experiment. Half were asked to sleep under normal atmospheric conditions (sea level) and half slept in an altitude chamber that could mimic the conditions of a plane’s cabin pressure at cruising altitude (8,000 feet, or 2,438 meters, above sea level).
Within each group, half were first assigned to drink a moderate amount of alcohol—about two drinks worth— right before bed, while the other half slept normally. After two recovery nights, the two halves swapped conditions (this kind of set-up is done to ensure that an important variable, such as drinking alcohol before bed, isn’t affected by the timing of the experiment). All in all, the team collected data from 23 volunteers in the control sleep lab group and 17 in the simulated high-altitude group.
Blood oxygen saturation is measured via a reading of our arterial oxygen partial pressure (PaO2), with a healthy level being above 95%. A level below 90% is considered low and could merit medical attention.
People resting in the sleep lab had normal blood oxygen levels throughout, though their heart rate did increase a bit on the night when they drank alcohol first. Those sleeping in the altitude chamber fared worse, especially after drinking. When drinking, their median blood oxygen level sank to 85%, compared to 88% when not drinking, and their heart rate increased more as well. The volunteers also had shorter bouts of deep and REM sleep while drinking compared to every other condition, both of which are important to our overall sleep quality.
The team’s findings, published in the journal Thorax, are based on a small sample size. The volunteers also slept in a typical supine position (lying face up), which is typically only possible for people flying first class. So it’s not clear yet whether the same pattern would be true for those drinking and sleeping while sitting. At the very least, it will take more research to confirm the potential additive effects of alcohol and long haul flying on the heart. But given that these changes could already be seen in perfectly healthy people, the authors are worried such a combination could be particularly dangerous to those in weaker cardiovascular health.
“Together these results indicate that, even in young and healthy individuals, the combination of alcohol intake with sleeping under hypobaric conditions poses a considerable strain on the cardiac system and might lead to exacerbation of symptoms in patients with cardiac or pulmonary diseases,” the authors wrote.
Medical emergencies on a plane are fairly rare (occurring around once in every 604 flights, according to a 2018 review), but 7% of them are attributed to cardiovascular problems. So it might be worth changing the rules around serving alcohol on long-haul flights, the authors argue, or at least making sure that people know about the possible danger.
“Practitioners, passengers and crew should be informed about the potential risks, and it may be beneficial to consider altering regulations to restrict the access to alcoholic beverages on board aeroplanes,” they wrote.
