For the Sake of Your Heart, Don't Drink on the Plane

"Please don't drink alcohol while being on an airplane." That's the advice of Dr. Eva-Maria Elmenhorst, a researcher at the German Aerospace Center's Institute of Aerospace Medicine and co-author of a new study showing the combination of alcohol, low air pressure, and sleep can trigger dangerously low blood oxygen levels in some fliers. "We were surprised to see that the effect was so strong," Elmenhorst tells NBC News. Both alcohol and low atmospheric pressure can reduce blood oxygen saturation, meaning the heart has to work harder to deliver enough oxygen to organs and tissues. Sleep also triggers a drop in blood oxygen levels, though not enough to be concerning. The problem comes when all three combine.

Normal blood oxygen saturation is 95% to 100%. When it drops below 90%, the body generally isn't getting enough oxygen to keep organs and tissues functioning properly. When it drops below 90% in people with heart disease, a heart attack, stroke, or blood clots could follow, Dr. Deepak Bhatt, director of the Mount Sinai Fuster Heart Hospital, tells NBC. The small study published Monday in Thorax involved 48 healthy adults aged 18 to 40 who were examined while sleeping sober and after consuming two alcoholic drinks. Half were examined in a lab with air pressure at sea level. The other half were examined in an altitude chamber with air pressure similar to that found on planes at cruising altitude, or 8,000 feet above sea level.

Researchers found blood oxygen saturation fell to 85% among those who drank before sleeping in the altitude chamber, compared with 88% in those who didn't drink, while heart rates rose to nearly 88 beats per minute on average. Among drinkers in the sleep lab, average blood oxygen saturation was 95% and heart rate at 77 beats per minute. "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 study reads, per Gizmodo. Indeed, "it may be beneficial to consider altering regulations to restrict the access to alcoholic beverages on board (airplanes)."