A recent study published in the journal Thorax found that drinking alcohol in-flight, combined with the low air pressure on airplanes, can have troublesome effects on your health. Mainly, it can drop your blood oxygen to worrying levels and speed up your heart rate. For folks with pre-existing health conditions, this is quite concerning.

Dr. Eva-Maria Elmenhorst is the co-author of the study and Deputy Head of Sleep and Human Factors Research at the German Aerospace Center. She emphasized that flying is already stressful on the body without alcohol. The dry cabin air can dehydrate you, and cramped seating can lead to blood clots. Plus, the lower oxygen levels at cruising altitudes (6,000 to 8,000 feet above sea level) mean your body gets less oxygen with each breath.

Researchers were surprised by the strong impact of alcohol in-flight

They found that blood oxygen saturation dropped to 85%, and heart rates rose to 88 beats per minute in people who drank alcohol before sleeping in an altitude chamber. For those who drank at sea level, oxygen levels only dropped to 95%, and heart rates increased to 77 beats per minute. Drops below 90% in oxygen saturation are considered concerning.

NBC News reported that several experts agree with the study’s conclusions. Dr. Deepak Bhatt from Mount Sinai Fuster Heart Hospital in New York supports the findings, suggesting that drinking on flights can pose serious risks, especially for people with heart conditions. The study could explain why drinking on flights might trigger heart attacks, strokes, or blood clots in susceptible individuals.

Mariann Piano, a nursing professor at Vanderbilt University, found the oxygen saturation drop particularly alarming. It indicates that it could affect the delivery of oxygen to body tissues. This is especially dangerous for those with chronic obstructive pulmonary disease, who already have lower baseline oxygen levels.

Dr. Prashant Vaishnava, a cardiologist at Columbia University, advises that people with underlying health issues should avoid alcohol when flying. Healthy individuals who really want a drink should limit themselves to one to avoid potential risks.

Overall, while the study suggests that healthy young people aren’t at serious risk, it highlights the importance of caution. So, think twice before drinking alcohol on a plane, especially if you have any health conditions and plan on napping during the flight.