Causes of Jet Lag

Jet lag happens when your internal body clock does not match the local time after you cross several time zones.

The main cause

The body clock (circadian rhythm) is set by light and dark and controls sleep, hunger, body temperature and hormones such as melatonin. After fast travel across time zones, the clock stays on home time for days and the new day-night pattern does not fit it.

What makes it worse

• Number of time zones crossed: more than 3 zones usually causes symptoms
• Direction of travel: flying east is usually harder than flying west, because it means going to sleep earlier than the body wants
• Sleep loss before and during the flight
• Alcohol and caffeine on the flight, which disturb sleep and cause dehydration
• Dry cabin air and long sitting
• Stress and a heavy travel schedule
• Age: older travellers often recover more slowly, and some people are more sensitive
• Light at the wrong time: bright light at the wrong hour can shift the clock the wrong way

Related factors

• Shift work and frequent travel add to the effect
• Existing sleep problems such as insomnia make jet lag harder

Not a disease

Jet lag is a temporary body clock mismatch and not an infection or a lasting illness.

Ayurvedic view

Ayurveda would describe it as Vata disturbance from travel, irregular routines and disturbed sleep. This is a traditional view and not a modern explanation.

Key point

Jet lag comes from a clock mismatch. Light timing, sleep habits and the direction of travel decide how severe it is.

Before your appointment

Note where and when you travelled, how many time zones you crossed, and how long your sleep problems have lasted. List all medicines, melatonin, herbs and supplements you take, and your caffeine and alcohol use. Mention snoring, low mood, anxiety, leg pain or swelling, and any existing conditions such as diabetes or epilepsy. If you are pregnant or travelling with a child, say so. Ask about safe sleep aids and the warning signs that need urgent care. Call 112 for chest pain or severe breathlessness.