If you’ve ever taken a long-haul flight east, chances are you have first-hand experience of how jet lag feels. There’s no mistaking that distinctive combination of exhaustion and insomnia, spiced up with a sense of unreality, a screwed-up appetite, digestive problems, lack of concentration and a liberal sprinkling of irritability. A bad bout can take a week to shake off, playing havoc with your productivity and personal relationships. And in the long term, the health consequences are potentially more serious.
Scientists have now linked repeated episodes of jet lag with a higher risk of heart disease, cancer, weight gain and mental health disorders such as depression. Take a stoic, “grin and bear it” approach to jet lag and you may be gambling with your future health.
But the good news for anyone facing an unavoidable schedule of eastbound flights is that anti-jet lag pills are in the pipeline and, in the meantime, we know more about how to minimise the impact.
We’ve long known that jet lag affects the body’s circadian clock – the 24-hour cycle of biological processes that exists in both animals and plants. “You need it to fine-tune your internal physiology – it’s your body clock that cranks up your metabolism, raises your temperature when you need to be alert, and winds it down when it’s time to rest,” says Russell Foster, professor of circadian neuroscience at the University of Oxford. The typical body clock actually runs fractionally longer than 24 hours, which is why adding hours to your day when you fly west seems to have less impact than shortening it (for example, trying to get to sleep at midnight local time when your body thinks it’s 5pm) by flying east.
And while it used to be thought that the body clock was in the hypothalamus, a grape-sized nodule at the base of the brain, we now know there is a body clock gene in every one of our cells. It’s these cells that directly influence the rhythms of the heart, lungs, liver and other organs. “The hypothalamus acts like the conductor of an orchestra, keeping them all in time,” says Dr Victoria Revell, a chronobiologist at the University of Surrey.
Fly from London to Hong Kong and, during an 11am meeting, when you need to be alert and capable of coherent conversation, your body would hit its lowest temperature point because if you were still at home, it would be 4am and you’d be in the deepest sleep of the night (usually three hours before waking).
“Forcing your body to be alert and active at a time it should be asleep triggers a stress response that lowers the immune system, and puts strain on the heart,” Foster says. “We know that even after 20 years, the body doesn’t adapt.”
Making a habit of living out of kilter with your body clock is also linked to cancer – studies suggest that nurses who work nights for many years on end are up to 36 percent more likely than average to get breast cancer. This may also explain why the disease is more prevalent in female cabin crew, and why prostate cancer is more common among long-haul pilots.
The suggestion is that disruption to the body clock interferes with the production of melatonin, a powerful, cancer-fighting antioxidant. Experiments have shown that breast cancer cells actually stop growing when exposed to the amount of melatonin that the brain manufactures at night.
Repeated bouts of jet lag could also influence your weight if you find yourself eating at a time you’d normally be asleep. “The body isn’t as efficient at processing fat at night-time, and the glucose-insulin response is impaired,” Foster says.
Missing sleep also has an effect – scientists at the University of Chicago found that after only a few days of cutting back to four hours’ sleep a night, people struggled to process glucose, in a similar way to the early stages of diabetes. And it takes only two nights of having two or three fewer hours’ sleep than normal to result in 15 percent more ghrelin (a hormone that boosts appetite), and 15 percent less leptin (the “full-up” hormone) being produced.
“It results in the brain receiving the message that the body’s intake has been cut by 900 calories a day. It’s the same feeling of hunger you’d get if you were on a low-calorie diet,” says Dr Shahrad Taheri, a senior lecturer from the University of Birmingham, who carried out the research.
But it’s not just your body that takes punishment from the regular crossing of time zones. Living out of sync with your natural rhythm can also have an impact on your brain, leading to memory problems, anxiety and depression. In a recent study on hamsters exposed to the equivalent of a New York to Paris flight twice a week for a month, jet lag created changes in the hippocampus, a part of the brain that controls memory processing, for up to a month afterwards. And research from a team at Liverpool John Moores University published in The Lancet found that cabin crew had a higher risk of experiencing mental health problems, including brief episodes of psychosis.
What we still don’t understand, however, is why jet lag seems to affect some people more than others. We know that it worsens the more time zones you cross in one flight, or in a series of flights within a few days, and that most people aren’t affected by journeys north or south because they don’t cross time zones.
Age may be a factor – a survey of 1,002 business travellers commissioned by British Airways a few years ago found that older executives reported fewer problems coping with jet lag than younger managers. “Most people tend to become ‘larks’ as they get older,” Revell says, “and people who are natural ‘larks’ will find flying east less disruptive than those who are ‘owls’.”
The researchers also suggested it may be down to self-selection – people who can tolerate jet lag are more likely to stick at a job that involves travel. Lifestyle factors can also influence how bad it feels, Revell says. “General fatigue will make jet lag symptoms feel worse, so sleeping on the plane, not drinking alcohol, and staying hydrated are important,” she says.
In the meantime, it’s possible to fly without jet lag if you gradually adjust your sleep schedules before flying, says Dr Charmane Eastman, director of the biological rhythms research laboratory at Rush University Medical Centre in the US. She devises personalised programmes of adjusted sleep times, exposure to bright light – from the sun or a light box – at specific times during the day, avoidance of bright light at other times, and melatonin supplements, which should mean you will hopefully arrive at your destination perfectly in sync with the time there.
In the week before a westward flight from London to LA, for example, you’d go to bed and get up two hours later each night for five nights before you depart. Flying east, you’d shift your sleep schedule earlier.
The downside is the practicality of going to bed before the kids and getting up in the middle of the night, or staying up until 3am and rolling into work just before lunch, for a week before you fly. But it could be worth it if there’s a lot riding on your performance at your destination, if you’re taking the holiday of a lifetime, or if you’re flying somewhere to take part in an extreme physical challenge.
“It’s used by athletes and the military,” Eastman says, “although I’d like to see it adopted by politicians and the diplomatic service, or anyone who is making important decisions on our behalf.” You can see her point when you consider that jet lag can reduce communication skills by 30 percent, memory by 20 percent, decision-making by up to 50 percent, and attention by 75 percent, according to research by leading sleep expert Dr Chris Idzikowski for BA.
Revell says: “Not making any attempt to shift your sleep schedule will prolong your jet lag. If you’re flying east and your trip is longer than two or three days, it’s worth making the effort to get up two hours earlier for a few days before you go, and preferably use an LED light [see panel, right] as soon as you get up.”
If that still sounds like too much effort, take heart – the race to license the first anti-jet lag pill is on. Pfizer is funding research by Andrew Loudon, a professor at the University of Manchester, who has discovered an enzyme, casein kinase, that controls the biological clock. “We’ve found that we can control one of the key molecules involved in setting the speed at which the clock ticks and, in doing so, actually kick it into a new rhythm,” he says. “We’ve shown that it’s possible to use drugs to synchronise the body clock of a mouse and so it may also be possible to use similar drugs to treat a whole range of health problems associated with disruptions of circadian rhythms. This might include some psychiatric diseases and certain circadian sleep disorders. It could also help people to cope with jet lag and the impact of shift work.”
A team from Germany’s Max Planck Institute is investigating how peaks and troughs in the hormone cortisol can influence circadian rhythms. They used a drug called metyrapone to adjust cortisol levels in mice. “By shifting the cortisol peak to an earlier or later time, one can alleviate jet lag in our mouse model and that strategy may also work in the case of humans,” says researcher Gregor Eichele. “We would want to develop a pill that one would have to take a day or so before travelling.”
For now, if you’re nodding off in your meeting, there’s always the tried-and-tested fallback of every business traveller –– the strong cup of coffee. Caffeine won’t eliminate the effects of jet lag, but it could help make them less obvious.
Jet lag therapy
You’ll find anti-jet lag treatments on the spa menu of most good hotels, and a relaxing massage is a better way of tackling insomnia than the minibar – alcohol disrupts the amount of deep and REM (rapid eye movement) sleep you get, so you don’t wake up refreshed.
* Therapists at Elemis spas (www.elemis.com) use a blend of sleep-promoting essential oils such as geranium, marjoram and lavender to relieve muscle tension and start the wind-down process. An invigorating massage early in the day, such as the “jet lag reviver” from Espa (www.espaonline.com) or the “energy re-balancing massage” at Hong Kong’s Regal Airport Hotel (www.regalhotel.com) could counter grogginess by improving blood flow to the brain.
* In the future, your hotel room could be the only therapy you need if more chains take their cue from the Westin Chicago River North (www.westinchicago.com), where showers are fitted with high-intensity lights to help reset your body clock, or London’s Rafayel (www.hotelrafayel.com), where river-view suites feature Philips’ Activiva anti-jet lag lighting.
Tips from frequent flyers
“Generally I take a nonstop day flight where possible, but where an overnight flight is the only option, a flat bed is a must. No late-night meal or alcohol on board or prior to the flight.”
“Never eat on the plane during a long-haul flight – eat at the correct local time when you land instead.”
“Set your watch to the time applicable at your destination as soon as the aircraft takes off and act on it for food and sleep.”
“The worst thing to do is take a nap when you arrive – try to stay awake until bedtime. This can be difficult but going for a walk or engaging in other physical activity helps.”
“The only time I avoid jet lag is when I completely cut out alcohol for a few days before I fly, and the whole time I’m away. I think it improves sleep quality.”
How to help yourself
* Time your light exposure. Russell Foster’s team at Oxford University recently discovered that there is a separate sensor in the eyes that detects light specifically to regulate the body clock. Put simply, exposure to light wakes you up, so getting out in daylight when you’ve flown west will help you stay up and adapt to local time – or switch on a portable LED light box for the last two hours of your flight. If you’ve flown east and wake up too early in the morning, avoiding bright light for the first few hours will help your body to adjust. Check out “Dr Sleep’s Jet Lag Advisor” on www.ba.com for personalised, journey-specific advice of when to seek and avoid exposure to light.
* Use your shades. Wear sunglasses on the plane to minimise exposure to bright light at inappropriate times. If you’re on a 9pm flight from New York to London, for instance, wear your sunglasses when they turn all the lights on for breakfast, and keep them on until you land. Then get lots of bright light on the ground.
* Have breakfast al fresco. This signals to your body that the day has begun. “Morning light is essential for synchronising our internal body on a daily basis,” says Surrey University’s Victoria Revell. “It can boost alertness and mood, and affect different levels of hormones.”
* Know your low-zone. You’ll feel worst when your body temperature hits its lowest point in its daily cycle. For most of us, it’s around 4am, approximately three hours before our usual waking time at home. If you can, avoid scheduling any meetings at your destination that coincide with that time at home.
* Don’t eat on the flight. New research suggests the brain has a second “feeding clock”, which keeps track of meal times, rather than daytime. In studies on mice published in the journal Science, when food is scarce, the feeding clock (dorsomedial hypothalamic nucleus) overrides the biological clock, keeping animals awake until they find food. “We discovered that a single cycle of starvation followed by re-feeding turns on the clock, so that it effectively hijacks all of the circadian rhythms on to a new time zone that corresponds with food availability,” says Dr Clifford Saper, a researcher at Harvard University. “Avoiding food on the plane and then eating as soon as you land should help you to adjust, and avoid some of the uncomfortable feelings of jet lag.”
* Sleep in pitch darkness. According to recent research, even a dim light in your bedroom (from a clock radio or the standby button of a TV) could interfere with the chemical structure of your brain. If you can’t block out all light, try sleeping with an eye mask. And if you have to get up in the night, avoid putting on any lights (keep a torch by your bed or night light in the hall). Even a short burst of brightness can temporarily suppress your body’s production of melatonin.
* Crank up the air con. Your body temperature naturally drops when you sleep, probably as a way of conserving energy. If your bedroom is so warm that this drop in temperature can’t occur, you won’t go into a deep sleep, and will wake up feeling groggy.
* Use melatonin (available on prescription from your GP). “A wide body of research indicates that melatonin pills do effectively shift the circadian clock and are a useful tool for reducing jet lag,” says Charmane Eastman of Rush University Medical Centre. “It seems to help you sleep or stay awake, depending on what time you take it.” Take 5mg in the afternoon when flying east (seven hours before you plan to go to bed at your destination). If you’ve flown west, take it when you get up in the morning.
* Get your “anchor sleep” – a minimum block of four hours’ respite during the local night – which is thought to be necessary to help you adapt to a new time zone.
* Get a personalised anti-jet lag schedule. Eastman devises a select few free of charge, in return for feedback. Contact [email protected]
