Why You Should Avoid Alcohol on a Long-Haul Flight

Enjoying an alcoholic drink before drifting off to sleep on a long-haul flight might put your heart health and sleep quality at risk, according to a small study.

The study involved using an altitude chamber designed to simulate in-flight conditions. Among the 17 participants who were in the altitude chamber, their median blood oxygen levels fell to 85%, and heart rates rose to 88 beats per minute after drinking the equivalent of two cans of beer or two glasses of wine and sleeping for four hours.

Normal blood oxygen levels for healthy individuals should stay between 95% to 100%. Levels below 92% signal that the body may have entered hypoxia, when there’s insufficient oxygen at the tissue level to maintain homeostasis. This could cause symptoms like confusion, difficulty breathing, and rapid heart rate.

This study only included healthy young adults, but people with pre-existing heart or lung conditions might be at a higher risk for hypoxia, which could be life-threatening.

“They might board the airplane with an already low oxygen saturation that might drop further during sleep after alcohol intake,” said Eva-Maria Elmenhorst, MD, lead author of the study and deputy of the Department of Sleep and Human Factors Research at the Institute of Aerospace Medicine at the German Aerospace Center in Cologne, Germany.

According to Elmenhorst, a combination of reduced blood oxygen levels and increased heart rate during sleep could challenge the cardiac system and lead to a medical emergency in flight, especially for people with pre-existing conditions.

Study Simulated First Class Conditions

The study participants slept lying down, a position only available to passengers in first or business classes. While this sample doesn’t represent all air travelers, Elmenhorst said passengers in these seating sections might have an additional risk since they have easier access to alcoholic beverages.

“We also only looked at one single dose of alcohol,” she added. “In the real world, passengers might consume more or less alcohol. It is likely that the effect on oxygen saturation is dose-dependent.”

Passengers who doze off in upright economy seats might not have the same experience as the study participants. Oxygen saturation levels drop when we sleep in any position, but these levels dip more in a supine sleep position, according to Younghoon Kwon, MD, a cardiologist and sleep medicine expert with the UW Medicine Heart Institute in Seattle, who was not involved with the study.

“When you are in a sitting position, the effect is probably not as dramatic as this,” Kwon told Verywell.

Regardless of seating positions, consuming alcohol in any environment can lead to poor quality sleep.

“Even though people believe that [alcohol] will help them fall asleep quicker, as a whole, your sleep quality is much worse as manifested in this study as well. Your shallow sleep stage goes up, and in trade, your REM sleep, which is considered good sleep, dramatically seems to go down,” Kwon said.

Flying Is a Stress Test for the Body

Airplane cabin pressure typically stays between 7,500 to 8,000 feet, which is about the altitude you would experience in Aspen, Colorado.

“There’s a bit of a stress test every time we fly,” Danny J. Eapen, MD, medical director of cardiac rehabilitation at Emory Saint Joseph’s Hospital, told Verywell.

The human body adapts to altitude changes by tightening blood vessels in the lungs and dilating blood vessels in the rest of the body, causing shifts in fluids and a rise in heart rate, Eapen said.

Humidity also drops in a plane cabin. The arid conditions may contribute to increased fluid loss and dehydration, even though you may not notice these changes immediately.

Eapen said that many people arrive at the airport hungry, tired, thirsty, and anxious about their flight, and adding alcohol to the mix is not a great combination.

“Flying is not benign. There are things that happen that will magnify underlying states before you enter into the plane,” Eapen said. “Think of it like being in a desert at 8,000 feet. That’s the environment you’re going to be in for one to 12 hours.”