Jet lag is a temporary sleep disturbance that can occur after travelling rapidly across several time zones. It happens because the body’s internal timing system remains aligned, for a while, with the time zone you left rather than the one you have arrived in.
Why jet lag happens
The circadian system helps coordinate sleep and wakefulness over roughly 24 hours. Light is one of its strongest timing signals. After a long-haul flight, local daylight, bedtime and mealtimes may suddenly occur several hours earlier or later than the body expects, producing tiredness, difficulty sleeping at the desired time and reduced concentration.
What may reduce its effects
The NHS advises travellers to arrive well rested where possible, adapt to the destination’s sleep schedule, spend time outside in daylight after arrival and avoid excessive alcohol or caffeine during the flight. Staying hydrated and moving around the cabin regularly are also sensible during long journeys.
Some travellers gradually shift their sleep and wake times before departure, particularly when crossing several time zones. The usefulness and timing of light exposure can differ depending on the direction and number of time zones crossed, so broad advice such as “always seek morning light” can be misleading.
Jet lag usually improves as the body adjusts. Persistent or severe sleep problems deserve a different assessment rather than being assumed to be jet lag. People with ongoing health conditions, or those considering medicines or supplements for sleep, should seek individual advice from a qualified healthcare professional.
For current general guidance, see the NHS information on jet lag.
