Don’t drink, sleep, and fly: The combined effects of alcohol and inflight sleep at cruising altitude on sleep quality, oxygen saturation and heart rate

Abstract

The hypobaric environment in an aircraft cabin at cruising altitude is known to impair sleep quality and decrease oxygen saturation (SpO₂) reaching lowest levels during sleep. Alcohol is frequently consumed inflight and, as potent somnogen, facilitates sleep. We examined the combined impact of hypobaric hypoxia and alcohol on SpO₂, heart rate, and sleep. Method: Two groups of healthy volunteers slept two nights with 4-hours duration (0:00 to 04:00 h), the Control Group under normobaric conditions (N=23, 9 females, mean age ± standard deviation 26.43 ± 5.75 years, sleep lab at 53 m altitude) and the InFlight Group under hypobaric hypoxia (N=17, 9 females, 26.41 ± 4.74 years, pressure chamber at 753 hPa simulating 2438 m altitude). In a counterbalanced design, participants consumed vodka one hour before bedtime on one of the two nights. The blood alcohol concentration 15 min before bedtime was 0.042 ± 0.015% in the Control Group and 0.043 ± 0.021% in the InFlight Group. Two 8-hour recovery nights were scheduled between conditions. Polysomnography and heart rate were analysed with mixed ANOVAs and Tukey-Kramer adjustment and SpO₂ with paired and unpaired Wilcoxon tests and Bonferroni adjustment. Results: The Control Group had a median (25th/75th percentile) SpO₂ of 95.88% (95.72/96.36) and heart rate of 63.74 bpm (55.55/70.98) during total sleep time (TST) of the non-alcohol condition which fell to 94.97% (94.59/95.33) and increased to 76.97 bpm (65.17/79.52), respectively, in the alcohol condition (both p<0.001). In the alcohol condition of the InFlight Group, SpO2 was 95% of TST (i.e. 201 min) below the hypoxia threshold of 90% SpO₂. SpO₂ was lower (85.32% (82.86/85.93)) and heart rate higher (87.73 bpm (85.89/93.86)) during TST compared to all other conditions (all p<0.001; non-alcohol condition InFlight: 88.07% (86.50/88.49), 72.90 bpm (70.90/78.17)). In the alcohol condition of the InFlight Group, REM and N3 duration were reduced (REM: compared to all conditions p<0.047; N3: compared to both laboratory conditions p<0.003). Conclusion: We observed clinically relevant desaturations of extended duration with pronounced cardiac response in healthy volunteers after moderate alcohol intake during sleep inflight. This might increase the emergency risk especially in older passengers and those with pre-existing medical conditions.