Joyce K. Lee-Iannotti, MD, FAAN, is a noted sleep expert, but even she was surprised by the severity of the jet lag she suffered after returning to Arizona from a meeting in Singapore.
Crossing 15 time zones meant the Phoenix-based physician’s brain was buzzing at 3 a.m. and slow-moving at noon. She was irritable, had trouble forming words, and sometimes felt like her heart was racing.
“It felt like circadian rhythm whiplash,” says Dr. Lee-Iannotti, chair of the American Academy of Neurology’s Sleep Section and Director of the American Academy of Sleep Medicine’s Board of Directors. “I’m a sleep neurologist, and I know about jet lag, but I think I underestimated the impact.”
Our bodies love to follow a schedule so they can prepare us for what happens next. If someone eats dinner at the same time each day, the body knows when to start the digestion process. When people follow a standard sleep schedule, for example sleeping from 11:00 p.m. to 7:00 a.m. every night, the pineal gland starts increasing production of melatonin before that standard bedtime to encourage the body to rest.
But traveling across multiple time zones confuses the body’s schedule. That’s why jet lag is also called “circadian misalignment.” While fatigue is the most common symptom of jet lag, the condition can affect the entire body, causing digestive issues, unexpected mood changes, and metabolic problems.
What Are Circadian Rhythms?
“Circadian rhythms are our body’s timekeeper,” says Karin Johnson, MD, a professor of Neurology at UMass Chan School of Medicine – Baystate and medical director of Bay State Health Regional Sleep Medicine. “The main thing that drives those rhythms is light exposure.”
Morning light tells the body to wake up and increasing darkness signals it’s time to rest. When we travel across time zones, we’re changing our standard exposure to light and dark.
“We generally say that it takes one day for each time zone crossed to readjust,” Dr. Johnson says. “It can get really complicated depending on how far you’re traveling.”
Moving west to east is generally harder on the body, but exactly how an individual responds to crossing time zones varies from person to person. Individuals who require a solid eight hours of sleep each night may be more impacted than someone who feels rejuvenated after six hours of rest.
How to Prevent Jet Lag
Frequent travelers are often eager to share tips for how to beat jet lag, but not all are based on science. Some believe walking barefoot on the ground upon arrival or walking with toes curled at one’s destination reconnects the body with the earth. Others suggest fasting before a flight, sniffing ginger or rosemary while in-flight, chewing gum when the plane is landing, or wearing sunglasses at your destination, even indoors.
Still, “general recommendations that aren’t physiologically grounded can be potentially harmful,” says Dr. Logan Schneider, MD, a sleep neurologist at the Stanford Sleep Medicine Clinic in Redwood City, CA.
Dr. Schneider often suggests using an online tool or phone app—like Jet Lag Rooster, Flykitt, and Timeshifter—to create a personalized plan to beat jet lag. These options use flight departure and arrival times, the number of time zones crossed, and an individual’s regular sleep habits to create multi-day adjustment plans. When Dr. Schneider is preparing to travel from his California home to the East Coast, he uses one of these options to prepare his body for the three-hour time difference.
Two days before a flight, Dr. Schneider adjusts his internal body clock by going to bed and waking up an hour earlier. If he needs help doing so, he knows that what works for him is to take a dose of a melatonin supplement five to six hours before he wants to sleep and use light therapy glasses to mimic morning sun to wake up. (Both of those items are small enough to pack in your luggage for the return trip.)
But pre-planning like this becomes much more difficult when there are more time zones to cross. “When you move beyond eight hours, you’re just going to suffer in one time zone or another,” Dr. Schneider says.
Still, there are ways a traveler can make a trip easier on their body. Before the flight, a traveler should aim for enough sleep in the days prior so they feel fully rested when arriving at the airport— “sleep-deprived individuals are more susceptible to jet lag,” Dr. Johnson says.
During the flight, travelers can determine whether they should sleep or stay awake by looking at their departure and destination times to figure out if they need to advance or delay their inner clocks. Someone who opts to sleep enroute might want to pack earplugs, an eye mask, and a neck pillow. Those who aim to stay awake should try to keep their bodies and minds occupied. That could mean walking around the plane and performing stretch exercises, watching a lively movie, or playing a game.
Dr. Lee-Iannotti could have made her reintroduction to Phoenix-time easier if she’d taken a few days off from work after returning. Using light therapy and a melatonin supplement could have helped reset her internal clock.
And even with a 15-hour time difference, she could have entered her travel details into a jet lag app while still in Singapore to see if there were small things she could do proactively to address the looming adjustments.
“It literally took me two and a half weeks to finally feel normal, and I was really struggling the entire time,” Dr. Lee-Iannotti says. “Jet lag is a true thing.”
Jet lag is more than a temporary inconvenience—it creates a disruption to the brain’s internal clock that can affect sleep, mood, thinking, and overall health. Neurologists emphasize that preparation, light exposure, and sleep timing are key tools for recovery. With evidence-based strategies, travelers can reduce symptoms and return to normal functioning more quickly.
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