Research from the NUS Yong Loo Lin School of Medicine in Singapore indicates that jet lag is more severe when travelling eastward due to the body’s circadian rhythm being disrupted.
The study examined data from 60,000 trips, revealing that sleep duration returns to normal within two days, while sleep timing recovery can take over a week.
Short trips of up to three time zones show a severe impact from jet lag, illustrating how even brief journeys can affect sleep patterns.
Younger adults are more adversely affected by sleep disruptions during long flights than older individuals, according to the study’s findings.
The researchers utilised 1.5m nights of data from the Oura ring, presenting the first large-scale study on jet lag recovery based on real-world conditions.
The work highlights the influence of cultural and regional factors, particularly work-related practices, on sleep variability and jetlag, calling for further exploration of these differences to understand normative sleep patterns globally.
Nocturnal sleep in Asia is shorter and starts later compared to other regions, yet sleep efficiency is lower and weekday sleep variability is higher.
Social Jetlag: Cross-country differences in social jetlag exist, though they are less pronounced than differences in weekend sleep extension.
Europe and the USA show longer weekend sleep extension compared to Asia, but this is only partially linked to shorter weekday sleep duration.
The study suggests that high weekday sleep variability and short sleep in some countries may indicate culturally distinct coping mechanisms for sleep debt, challenging the use of weekend sleep extension as a universal indicator of sleep debt.
In an earlier study published in Sleep Medicine (2023), Willoughby and colleagues analyzed over 50m nights of sleep data from approximately 220,000 users across 35 countries, with each participant contributing an average of 242 nights of data. The study examined sleep duration, timing, efficiency, weekday sleep variability, weekend sleep extension, and social jetlag, assessing the impact of country of residence through multiple regression analysis.
Adrian Willoughby, the study’s lead author shared “We’ve known for some time that jet lag is a challenge for travellers. This study provides data-driven evidence of just how persistent the impacts are. Crossing time zones complicates this recovery by disrupting the ability to fall asleep at the appropriate local time.”
