Young passenger enjoying drink during flight

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WASHINGTON — If you typically enjoy a cocktail or two when you fly, you might want to do your best to stay awake. A new study reports that the combination of alcohol consumption and sleeping at high altitudes can lead to significant drops in blood oxygen levels and increased strain on the heart, even in young, healthy individuals.

Commercial airplanes are typically pressurized to an altitude of around 8,000 feet (2,438 meters) — about the height of a small mountain. At this altitude, the air is thinner and contains less oxygen than at sea level. While the body can usually adjust to these conditions, adding alcohol to the mix may disrupt this delicate balancing act.

Methodology

The study, conducted by researchers at the German Aerospace Center, involved 40 healthy participants between the ages of 18 and 40. They were divided into two groups: one that slept in a normal sleep laboratory at sea level (53 meters) and another that slept in a simulated airplane environment inside an altitude chamber pressurized to 2,438 meters, equivalent to the air pressure inside a plane at cruising altitudes.

Within each group, participants spent one night sleeping after consuming alcohol (vodka) and another night sleeping sober. The amount of alcohol was calibrated to bring their blood alcohol level to 0.04%, roughly equivalent to two beers or two glasses of wine. Sleep was limited to a 4-hour window from midnight to 4 A.M. to mimic a typical inflight sleeping period.

Results

The results, published in Thorax, were eye-opening. The “passengers” who drank alcohol before sleeping at altitude saw their blood oxygen saturation plummet to a median of 85%, with some dipping even lower. In contrast, the sea-level group who consumed alcohol only dropped to 95%. Spending too much time with oxygen levels below 90% can be considered clinically relevant hypoxia, a state of oxygen deprivation. Surprisingly, the altitude group that didn’t drink still spent over 80% of their sleep time in this hypoxic state.

As if gasping for air wasn’t enough, the altitude plus alcohol group also experienced significant jumps in heart rate as their cardiovascular system attempted to compensate for the lack of oxygen. Median heart rates reached 88 beats per minute, compared to 77 in the sea-level drinkers and just 63 in the sober sea-level sleepers. Over the course of a long flight, this extracardiac strain could be a concern, especially for older travelers or those with preexisting health conditions.

Sleep quality also took a hit under the influence of alcohol and altitude. Participants spent less time in the restorative stages of deep sleep and REM, while being awake more often after initially falling asleep. This suggests that inflight snoozing after a few drinks may not be as restful or refreshing as travelers would hope.

Study Limitations

While the findings are sobering, they come with a few caveats. The study only looked at the first four hours of sleep, and participants slept in a supine position, which is more feasible in first or business class. Economy passengers sleeping upright in cramped seats might be less affected. Other factors like noise, comfort, and the timing of alcohol consumption could also influence the results.

The sample size was relatively small and only included young, healthy adults, so the results may not fully represent the general population. Older individuals or those with preexisting health conditions could potentially experience more severe effects.

Discussion & Takeaways

Still, the results suggest that the common practice of enjoying inflight libations before catching some shuteye may not be as harmless as it seems. This is especially the case for those who may be more vulnerable due to age or health status. The high-altitude environment already puts stress on the body, and adding alcohol appears to amplify these effects. For some passengers, this could potentially lead to adverse health outcomes or even medical emergencies.

“Cardiovascular symptoms have a prevalence of 7% of inflight medical emergencies, with cardiac arrest causing 58% of aircraft diversions,” the authors write.

It’s important for passengers to remember that while planes are pressurized, the air at cruising altitude still contains significantly less oxygen than at sea level. Alcohol impairs the body’s ability to absorb and utilize the limited oxygen available. Over long flights, this could place undue strain on the cardiovascular system.

Abstaining from alcohol entirely or at least moderating intake could help mitigate some of the potential risks.

Airlines and healthcare providers may also want to consider these results when formulating guidelines or advice for passengers. While more research is needed to fully understand the scope of the issue and its implications, this study serves as an important reminder that the unique stresses of the inflight environment should not be underestimated.

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