Why do airplanes make me sleepy?

Why Airplanes Make Us Sleepy: The Science Behind the Drowsy Effect

Air travel is a common experience for many, but some may notice an unusual side effect: drowsiness. While the reasons for this are complex, research has identified a key factor that contributes to the phenomenon – subtle changes in air pressure.

Cabin Air Pressure and Oxygen Levels

Commercial airplanes maintain a cabin air pressure equivalent to altitudes of approximately 6,000-8,000 feet above sea level. At such heights, the air pressure is naturally lower than at ground level. As a result, the partial pressure of oxygen in the cabin is also slightly reduced compared to the ground.

Mild Hypoxia and Fatigue

This mild reduction in oxygen intake, known as hypoxia, is typically harmless at aircraft altitudes. However, it can lead to subtle changes in brain function, including a reduced level of arousal. This decrease in alertness can manifest as drowsiness and fatigue, making a nap particularly inviting during air travel.

Additional Factors

While cabin air pressure is a primary factor in airplane drowsiness, other factors may contribute to the effect. These include:

• Recirculated Air: Air conditioning systems in airplanes recirculate a significant portion of cabin air. This can lead to higher levels of carbon dioxide, which can further contribute to fatigue.
• Reduced Humidity: Aircraft cabins tend to have low humidity, which can dry out nasal passages and airways, making breathing less comfortable and potentially inducing drowsiness.
• Motion Sickness: Some people experience motion sickness during air travel, which can lead to nausea, dizziness, and drowsiness.

Conclusion

The subtle reduction in cabin air pressure on airplanes, mimicking high altitudes, leads to a mild decrease in oxygen intake. This mild hypoxia, while generally harmless, can induce drowsiness and fatigue, making a nap feel appealing during air travel. While other factors may also contribute to airplane drowsiness, cabin air pressure remains a key contributing factor to this common experience.