What is jet lag?

The flights are over, the bags are unpacked ( or maybe not quite yet!) - but your sleep hasn’t quite caught up. Jet lag is one of the most frustrating parts of travel, lingering well beyond the journey and affecting how you sleep, think, and feel during the day. Read on to find out what is jet lag and why it affects your overall sleep.

What is Jet Lag?

Jet lag happens when your body’s internal clock, known as the circadian rhythm, becomes misaligned with the local day–night cycle after crossing time zones. This clock regulates sleep, alertness, hormones, and body temperature. When travel is rapid, your body continues to operate on “home time,” even though your environment has changed. This makes it harder to fall asleep at the new bedtime, leads to lighter and more fragmented sleep, and can cause early waking or daytime sleepiness. Jet lag is often intensified by long flights, disrupted routines, dehydration, and prolonged sitting. Changes in light exposure play a major role, as light is the strongest signal for resetting the body clock. Alcohol used to fall asleep and excess caffeine used to stay alert can further disrupt sleep and delay adjustment.

Overcoming Jet Lag

Recovering from jet lag takes patience, but several strategies can help. Gradually adjusting your sleep schedule before travel, getting appropriate daylight exposure at your destination, and keeping regular meal times can support circadian realignment. Staying hydrated, limiting alcohol, avoiding late naps, and maintaining a consistent bedtime routine can also improve sleep quality during recovery.

How Long Does Jet Lag Last

Jet lag typically lasts about one day for each time zone crossed. For example, crossing five time zones may take around five days to fully adjust. Eastward travel often takes longer to recover from than westward travel, as it requires falling asleep earlier rather than later.

The Impact Of Jet Lag On Sleep Rebound, Fragmented Sleep, And Daytime Fatigue

After travel-related sleep disruption, the body often responds with what is known as sleep rebound. This is a natural drive to recover lost sleep by pushing more quickly into deeper stages of sleep once rest finally occurs. While this may sound beneficial, deeper rebound sleep is associated with reduced muscle tone in the upper airway, which can increase snoring and breathing disturbances in susceptible individuals. At the same time, jet lag commonly causes fragmented sleep. Frequent awakenings, early morning waking, and difficulty maintaining sleep are common while the body clock is misaligned. These interruptions prevent sustained deep and REM sleep, reducing the restorative quality of sleep even when total time in bed seems adequate. The combined effect of rebound sleep and fragmentation often leads to persistent daytime fatigue. People may feel heavy, foggy, or mentally slowed during the day, with reduced concentration and motivation. This fatigue can linger for several days after travel, particularly as work and daily responsibilities resume, making jet lag feel more disruptive than expected.

That said, is it going to stop me from going on a holiday? Not really, but a few handy tips won’t go to waste! Stay tuned for SleepWise’s Sleep Better Hub articles on jet lag, the science behind it and helpful hints on how to manage jet lag