Alcohol and stress pose risks to airplane passengers’ hearts

The researchers compared a group of 23 people sleeping in a laboratory to another group of 17 people who did so in an altitude chamber replicating the conditions that occur at an altitude of about 2,400 meters above sea level. Combination of alcohol consumption and hypobaric hypoxia during the simulation «Decreased sleep quality, stress on the cardiovascular system, and prolonged hypoxemia,

The study suggests that the greater the alcohol consumption, the more pronounced these effects may be, particularly in older travellers and those with pre-existing medical conditions. The researchers suggest it’s time to consider restricting access to alcohol on long-haul flights.

Atmospheric pressure decreases rapidly with altitude, causing blood oxygen saturation levels to drop to about 90% in healthy travellers at high altitude. A further drop in SpO2 below this limit is defined as Hypobaric HypoxiaA condition of low blood oxygen.

Alcohol relaxes blood vessel walls, which increases heart rate during sleep, an effect similar to hypobaric hypoxia. The researchers wanted to find out if the combination of alcohol and cabin pressure at cruising altitude could have an additional effect on sleeping passengers.

The study randomly divided 48 people between the ages of 18 and 40 into two groups. Half were assigned to a sleep laboratory in normal air pressure (sea level) conditions and the other half were assigned to an altitude chamber that simulated cabin pressure at cruising altitude (2438 meters above sea level).

Reversible process

Twelve people in each group slept for 4 hours without drinking, while the other 12 slept for 4 hours after drinking alcohol overnight. After two nights of recovery, the process was reversed.

Participants drank the equivalent of 2 cans of beer (5%) or 2 glasses of wine (175 ml, 12%) in pure vodka at 11:15 p.m., and their sleep cycles, SpO2 and heart rates were continuously monitored until 4 a.m.

The final analysis included results from 23 people in the sleep lab and 17 people in the altitude chamber. The results showed that the combination of alcohol and simulated cabin pressure at cruising altitude caused an average drop in SpO2 of more than 85% and an average compensatory increase in heart rate of about 88 beats per minute during sleep.

In comparison, those sleeping in the high-altitude chamber without alcohol showed a SpO2 of slightly over 88% and a heart rate of just under 73 beats per minute. In the sleep lab, those who drank alcohol had a SpO2 of just under 95% and a heart rate of just under 77 bpm, while those who did not drink showed a SpO2 of just under 96% and a heart rate of just under 64 bpm.

Oxygen levels below the clinically healthy range (90%) lasted for 201 minutes with the combination of alcohol and simulated cabin pressure, compared to 173 minutes without alcohol and 0 minutes under normal sleep laboratory conditions.

Additionally, deep sleep (stage N3) was reduced by 46.5 minutes under combined exposure to alcohol and simulated cabin pressure, compared to 84 minutes with alcohol and 67.5 minutes without alcohol in the sleep laboratory. Those exposed to hypobaric hypoxia and alcohol also had shorter REM sleep durations, both stages important for sleep recovery.

The researchers acknowledge the small sample size and that the participants were young and healthy, which does not reflect the general population. Additionally, the participants slept in a supine position, a luxury usually only afforded to those flying first class, so the findings may not apply equally to most economy class passengers.

However, they concluded that “these results demonstrate that, even in young, healthy individuals, the combination of alcohol consumption with sleep under hypobaric conditions places considerable stress on the cardiovascular system and may exacerbate symptoms in patients heart or lung disease». These effects may be greater in older people, suggesting that “professionals, passengers and crew should be informed of the potential risks, and it may be beneficial to consider modifying rules to restrict access to alcoholic beverages on board the aircraft.”

In statements to the Science Media Center, Esteban Ortiz Prado, professor and researcher at the University of the Americas (Ecuador), has clarified that although the findings are interesting and come from a well-conducted and controlled experimental model, “it is important to interpret them with caution. Taking this study out of context could cause unnecessary anxiety in passengers, leading them to avoid moderate alcohol consumption during flights, when in reality, with an adequate diet, this moderate consumption should not represent a significant health risk.”