Travel Health: Jet Lag
Crossing multiple time zones throws your body clock off balance. Here's everything you need to know to arrive at your best.
Jet lag is a temporary but disruptive sleep disorder that occurs when you travel rapidly across multiple time zones. Your body's internal clock — the circadian rhythm — stays tuned to your home time zone while the world around you operates on a different schedule, causing a mismatch that can take days to resolve.
🕐 What is Jet Lag?
Our biological clock is synchronised with local light and darkness, regulating when we feel hungry, alert, and sleepy. When you fly across multiple time zones in a matter of hours, your body hasn't had time to adapt — it still expects daylight when it's dark, and sleep when it's morning. This mismatch is jet lag.
Jet lag is temporary and not dangerous for most travellers, but it can significantly affect your comfort, productivity, and enjoyment of your trip — especially in the first few days after arrival.
🤒 Symptoms of Jet Lag
Symptoms vary from person to person. You may experience just one or several at once, and severity typically increases with the number of time zones crossed.
Fatigue & Sleepiness
Feeling exhausted during the day or struggling to stay awake at inappropriate times.
Cognitive Effects
Memory lapses, difficulty concentrating, and a general "brain fog" feeling.
Digestive Upsets
Nausea, constipation, diarrhoea, or loss of appetite due to disrupted gut rhythms.
Irritability
Mood swings and short-temperedness are common, particularly after eastward travel.
Menstrual Disruption
Women may experience delayed or irregular periods after long-haul travel. Those on oral contraception should be aware of timing complications when adjusting to a new schedule.
Disrupted Sleep
Difficulty falling asleep, staying asleep, or waking far too early at your destination.
⏱️ How Long Does Jet Lag Last?
A useful rule of thumb: allow one to three days of recovery for each time zone crossed. So a flight from London to New York (5 time zones) could mean up to 5–15 days of adjustment — though most people feel significantly better after 3–5 days.
⚠️ Long-Term Consequences
For occasional travellers, jet lag is a temporary inconvenience with no lasting health effects. However, research on frequent flyers — particularly airline crew and shift workers — tells a more concerning story.
- Elevated risk of weight gain and metabolic disruption
- Increased likelihood of developing type 2 diabetes
- Chronic fatigue and cognitive impairment
- Higher rates of mood disorders including anxiety and depression
- For pilots and crew: potential safety implications due to reduced alertness and slower reaction times during duty
🏅 Jet Lag and Athletes
International travel is unavoidable in modern elite sport, and jet lag can significantly undermine performance for both individual athletes and entire teams.
📉 Performance Impacts
- Reduced accuracy and reaction time
- Increased rate of errors and poor decisions
- Decreased strength and endurance
- Higher injury risk due to fatigue
🧘 Managing It as an Athlete
- Travel several days before competition when possible
- Work with a sports medicine doctor on a sleep protocol
- Use light exposure strategically to reset the body clock
- Discuss melatonin use with a team physician
🛩️ Jet Lag and Airline Crew
Pilots and cabin crew regularly work across time zones and during hours when their body clocks expect sleep. This creates a unique and persistent challenge that aviation authorities and airlines manage through strict rest regulations — though fatigue remains an ongoing safety concern in the industry.
Crew members frequently begin duty periods without being fully rested, and periods of peak fatigue can coincide with critical phases of flight. Understanding and managing this risk is a central part of modern aviation safety.
💡 How to Minimise Jet Lag
- Get well-rested in the days before departure — starting tired makes jet lag much worse.
- Eat well and exercise regularly in the week before your trip.
- Gradually shift your sleep schedule 2–3 days before departure: go to bed 1–2 hours later if travelling west, or earlier if travelling east.
- If you take regular medication (e.g. for diabetes or blood pressure), consult your doctor in advance about adjusting your dosing schedule to the new time zone.
- Change your watch to the destination time zone as soon as you board.
- Stay hydrated — cabin air is very dry. Drink water regularly.
- Limit caffeine and alcohol — both disrupt sleep quality and worsen dehydration.
- Move around — walk the aisle and stretch your legs and arms regularly on long-haul flights.
- Sleep strategically — try to sleep if it is night at your destination. Eye masks and earplugs can help.
- Adopt local time immediately — eat meals and sleep according to the local schedule, not your home time.
- Get outside in natural daylight — sunlight is the most powerful reset for your body clock.
- Stay awake until local bedtime on your first day if at all possible — avoid napping if it's daytime.
- Exception: if your stay is 2 days or fewer, it may be more practical to remain on home time rather than adjusting.
💊 Medications, Melatonin & Alcohol
Melatonin is a naturally occurring hormone that regulates sleep. Some studies suggest it can help reset the body clock when taken at the right time, and it is widely available over the counter in many countries. However, the U.S. Food and Drug Administration (FDA) does not regulate melatonin, and its safety is not fully established — dosing, timing, and interactions vary. Discuss this with your doctor before travelling.
Sleeping tablets are not recommended during flights. While they may help you sleep, they increase the risk of DVT (deep vein thrombosis) by reducing movement, and they can leave you groggy on arrival.
Alcohol may seem to help you fall asleep, but it fragments normal sleep cycles and is likely to make jet lag worse — not better. Combined with the dehydrating effects of a pressurised cabin, alcohol is best avoided or kept to an absolute minimum during long-haul flights.
References
- Harvard Health, 2020 — health.harvard.edu
- Mayo Clinic, 2021 — mayoclinic.org
- Patient.info, UK — patient.info
- Aspetar Sports Medicine Journal, 2021 — aspetar.com
- Leaders in Sport, 2021 — leadersinsport.com
- Verywell Fit, Dotdash Publishing, 2021
- Institute of Aerospace Medicine, DLR — dlr.de
- CDC, 2019 — wwwnc.cdc.gov
- StatPearls, 2021 — ncbi.nlm.nih.gov
- Better Health Victoria, Australia, 2020 — betterhealth.vic.gov.au