Jet lag is worse when travelling eastwards, according to new research.
And young adults feel the negative effects on sleep of long flights more than people in their 60s, say scientists.
The biggest ever study of its kind found that travel-related sleep disruption takes even longer to recover from than previously thought.
The findings showed that while sleep duration recovers quickly, sleep timing can take “significantly longer” to realign when traveling across time zones.
Researchers at the Centre for Sleep and Cognition at the NUS Yong Loo Lin School of Medicine in Singapore teamed up with Finnish tech firm Oura Health to analyse sleep patterns during 60,000 trips of more than 600 miles.
The team used 1.5 million nights of de-identified data from the Oura Ring – a smart device used to track sleep and physical activity – to provide the first large-scale, real-world study of jet lag recovery to date.
The research team explained that previous studies on jet lag have either been conducted under controlled laboratory conditions or involved specific groups, such as athletes or military personnel, whose characteristics may not reflect those of the general traveling public.
Study lead researcher Dr. Adrian Willoughby, Senior Research Fellow at NUS Medicine, said: “We’ve known for some time that jet lag is a challenge for travellers, but this study provides data-driven evidence of just how persistent the impacts are, particularly when it comes to adjusting sleep timing to a new time zone.”
Dr. Willoughby pointed out that jet lag is a known cause of sleep disturbance during travel, but it is not the only factor.
He said that travellers often wake up early to catch flights, shortening sleep the night before departure.
While flights later in the day tend to have less impact on sleep the night before traveling, the researchers said sleeping on overnight flights poses challenges, often leading to impaired performance and increased daytime sleepiness.
Dr. Willoughby said, “This restricted sleep typically results in early bedtimes and extended recovery sleep the next night.
“However, crossing time zones complicates this recovery by disrupting the ability to fall asleep at the appropriate local time.”
The study found that the sleep duration usually returns to normal within around two days.
But changes in sleep timing and structure – such as more night time awakenings – can take more than a week, with eastward travel and crossing multiple time zones amplifying the disruption.
Jet lag was more severe following eastward travel – especially for shorter trips of up to three time zones, according to the study published in the journal Sleep.
But for longer journeys, the disruption from habitual sleep patterns was similar, regardless of direction, with sleep occurring 60 to 70 minutes earlier or later than usual.
In some cases, restoring normal sleep timing and structure can take more than a week.
The findings also showed that sleep duration generally recovers quickly, aligning within 15 minutes of habitual sleep duration within the first few days post-travel.
The researchers found minimal differences between men and women in travel-related sleep disruption.
However, older travellers experienced slightly less impact, with a 20-year-old experiencing a 15-minute greater reduction in sleep compared to a 60-year-old over the initial post-travel days.
A notable feature of the study was its measurement of habitual sleep before travel over an extended period as well as a long post-travel follow up.
Professor Michael Chee, director of the Centre for Sleep and Cognition at NUS Medicine, said: “Wearable devices like Oura Ring that track health behaviours over time, are opening new doors for health data collection on a large scale.
“Travellers looking at this dataset can determine how much better or worse off they are than the population average given their existing sleep habits, trip parameters, and number of days after travel.”
He added: “People like to know where they stand compared to others and this dataset provides a solid basis for assessing that.”
The research team said future work will assess lifestyle factors contributing to slower or faster recovery from jetlag, and whether efforts to time light exposure and melatonin ingestion help.
Source: Talker News / Digpu NewsTex
