Drinking on a plane has a unique effect on your body

You’re settled into your long-haul, international flight. The cabin pressure has stabilized, the seat belt sign is off, and the bar cart is heading down the aisle. Finally time to unwind—and there’s nothing like a Bloody Mary or a glass of wine to help you doze off for a few hours, right? Perhaps you consider a drink-induced nap a necessity, to stave off jet lag or anxiety.

As relaxing as it might seem, that drink might be doing more harm than good. New research found that alcohol compounds the effects of high altitude on people’s bodies, putting an extra burden on the cardiovascular system, reducing blood oxygen levels, compounding dehydration, and impairing sleep quality. It can also make you even more anxious.

“Why not just avoid drinking it in a situation that is already stressful for the body?” says study author Eva-Maria Elmenhorst.

Still, questions remain about how exactly alcohol may interfere with the in-flight experience, especially sleep—and who’s at greatest risk of health impacts. Experts discuss the science behind this research and what passengers can do to avoid the worst effects.

The additive physiologic effects of alcohol and altitude 

Much like ascending a mountain, flying puts a strain on the body. With increased altitude comes decreased air pressure, which decreases the concentration of oxygen in the air—also known as hypobaric hypoxia—and results in reduced oxygen in our lungs and bloodstream (called hypoxemia).

Although airplanes are pressurized to minimize the impact, a plane at standard cruising altitude (30,000 to 40,000 feet) would still have a cabin pressure matching that of an altitude above sea level, around 8,000 feet, says Peter Hackett, a high altitude expert and emergency physician. For a healthy person, that amount of elevation gain may not be noticeable, especially because our bodies have natural adaptation mechanisms.

“Your heart rate’s higher, you breathe more—either take more breaths each minute and/or take deeper breaths,” says physician and University of Washington professor of pulmonary, critical care, and sleep medicine Andrew Luks. These are just some of “a whole range of physiologic responses in the body, most of which are intended to help your body adjust to the low oxygen conditions and compensate for it.”

However, consuming alcohol may disrupt this response, Hackett says. Though the mechanisms are not fully understood, experts suspect that alcohol inhibits ventilation and, thus, oxygen intake. “[Alcohol] is what we call a respiratory depressant,” Hackett says. While a sober body will respond to high altitude by increasing breathing rates, he says, “alcohol blunts that response.”

Indeed, the researchers found that participants who consumed alcohol before sleeping at simulated high altitude clocked elevated heart rates (15 bpm higher than non-drinking participants) and decreased blood oxygen levels (three percent lower blood oxygen concentration than sober group). Both of these effects strain the cardiovascular system. 

You May Also Like

SCIENCE

Why hiking is uniquely beneficial for your body and your brain

SCIENCE

This is the biggest health challenge women face in their 40s

SCIENCE

These are the biggest health challenges women will face in their lifetimes

Why sleeping in-flight is a challenge even without a drink

Sleep quality and duration already suffer at high altitude, even for healthy and sober folks, according to Luks. “People spend much less time in the deeper stages of sleep and in REM sleep,” he says. Lower oxygen levels cause people to wake up more frequently and experience periods of breathing punctuated by periods of apnea, a phenomenon called periodic breathing. 

Of course, all the noise, turbulence, cramped seats, and frequent interruptions of a flight also contribute to a less than ideal sleeping environment. “There are any number of other things that are equally contributing to the problem,” Luks says. 

Although a glass of wine might seem like a good relaxant, alcohol actually has an adverse effect on sleep quality, Piano says. Even at sea level, alcohol has been shown to elevate heart rates, which can interfere with REM sleep and disrupt cardiovascular relaxation.

“When you drink a lot of alcohol, it does have a depressant effect, and you feel sleepy,” she explains. “But as you’re sleeping, your blood alcohol level is declining and, at certain blood alcohol levels, it actually becomes more of a stimulant and it wakes you up.”

The circulation of dry, cool air on flights has a dehydrating effect that can be exacerbated by alcohol. Alcohol inhibits antidiuretic hormones, which cause people to urinate more frequently, removing water from the body—and further interrupting sleep. Add the disruptive effects of altitude on breathing and rest, and you have a recipe for a fairly restless flight.

Alcohol and altitude affect some more than others

The mix of alcohol and altitude caused healthy participants in Elmenhorst’s study a degree of cardiac stress that Hackett says is comparable to “taking a walk.” The drop in oxygen levels, on the other hand, could cause headaches or dizziness, though he says it’s likely negligible for people in good health.

Luks agrees, noting that young, healthy people—including all of the participants in the study—“can generally tolerate fair degrees of hypoxemia.” While reduced oxygen levels over a prolonged period can cause tissue damage, in most cases, such as on flights, even the compounded effects of alcohol and altitude are mild, short-term, and will recede shortly after returning to sea level.

The implications may be more serious among people who are older or suffering from preexisting conditions, like heart or lung diseases, says Mariann Piano, a substance abuse expert and professor of nursing at Vanderbilt University. Theoretically, she says, an increase in heart rate or a drop in oxygen saturation levels could cause an “acute physiologic consequence,” such as heart failure. 

Practical tips for those who like to partake

If that casual inflight drink isn’t something you’re quick to forgo, experts offer some tips to minimize sleep and health impacts.

Piano recommends consuming no more than one alcoholic beverage over the course of a flight. Best to have that glass of wine or cocktail with food and supplement with extra water, she adds. And, as on land, the effects of alcohol are stronger on an empty stomach. 

Ultimately, when looking at the effects of alcohol, it “always comes down to a question of how much,” Luks says. “Go ahead and have a beer or a glass of wine, but don’t overdo it.”