For Australians, almost every big overseas trip means crossing many time zones. Here’s what jet lag actually is, why some flights hit harder than others, and what the science says helps.
Jet lag is a temporary sleep problem that happens when you travel quickly across several time zones. Your body is still running on the time back home, while the clock around you says something else.
Symptoms can include trouble sleeping at night, tiredness during the day, difficulty concentrating, headaches, an upset stomach and a general feeling of being unwell.
The body clock
Almost every cell in the body runs on a roughly 24-hour cycle, known as the circadian rhythm. It controls when we feel sleepy and alert, as well as body temperature, hormones and digestion.
A master clock in the brain keeps those rhythms in sync, mostly using light. Daylight entering the eyes tells the brain what time it is.
After a long flight, that clock needs time to adjust. A common rule of thumb is that it shifts by about an hour a day, although that varies from person to person.
Why east is harder
Most people find flying east harder than flying west.
The body’s natural clock tends to run slightly longer than 24 hours, so it’s easier to stay up later and stretch the day, as when flying west, than to fall asleep earlier and shorten it, as when flying east.
For Australians, flights to the U.S. and South America head east, while flights to Europe head west, although they cross so many time zones that both can be tough.
The flight itself
Long-haul flights can add to the problem. Cabin pressure, dry air, sitting still for many hours and poor sleep can leave travellers feeling worse, whether or not they’ve crossed time zones. Airlines have designed newer aircraft, such as the Boeing 787 and Airbus A350, with higher cabin humidity and lower cabin altitudes to reduce fatigue.
What helps
Light is the most powerful tool. Getting daylight at the right time of day, and avoiding bright light at the wrong time, helps the body clock adjust faster.
Other tips from sleep experts include gradually shifting sleep times before travelling, setting your watch to the destination’s time when you board, drinking water, limiting alcohol and caffeine, and trying to stay awake until a normal local bedtime on arrival.
Melatonin, a hormone that helps regulate sleep, is sometimes used for jet lag. In Australia, it’s available over the counter only for people over a certain age, and otherwise requires a prescription. Travellers should check with a doctor or pharmacist.
Research flights
Qantas worked with the University of Sydney’s Charles Perkins Centre to study ways to reduce jet lag on ultra-long-haul flights, including meal timing, lighting and movement, as part of its Project Sunrise plans for direct flights from Sydney and Melbourne to London and New York.
