by Dr. Milton Lum
The world, which is a sphere, is divided up into 24 time zones. The basis for world time is the Greenwich meridian, which is an imaginary longitudinal line passing through Greenwich village in London. The time changes by an hour for every 15° travelled in either direction from the Greenwich meridian. When one goes westwards, one gains time; when one goes eastwards, one loses time.
Jet travel enables a person to travel long distances over several time zones. When one travels over at least more than 3 time zones, one may experience jet lag. The traveller's body clock is disrupted as the body has to adjust to a new routine that is different from what the traveller is usually accustomed to. The body will need time to adjust to the time. In short, jet lag is a sleep disorder that occurs when the body's biological clock does not correspond to local time.
Anyone can get jet lag. It is more common in those who are more than 50 years old and much less common in infants and children. However, it does not occur in everyone who travel long distances.
Jet lag may be challenging for frequent flyers or those who travel across several time zones. However, it does not cause serious or chronic health problems.
Everyone has a body clock, which is also called 'biological clock' and 'circadian rhythm'. It controls not only the time when sleep is required and when one is awake, but also other important body functions like hunger, body temperature regulation, production of hormones, blood pressure, bowel habits and urine production.
The body clock is usually in tandem with the local time. All the rhythms are regulated by internal and external factors that interact. This means that one feels sleepy in the night and hungry and active in the daytime.
When a traveller crosses several time zones, the body has to adjust to the new times of light and darkness as well as other body functions such as sleep and activity cycle and associated changes in physical and mental functioning. The body has to re-establish its circadian rhythm.
It is believed that the oxygen levels in the cabin of the aeroplane influence jet lag. The cabin air is at a lower pressure than on the ground. This leads to a lower oxygen concentration in the blood, thus affecting the physical and mental abilities of the traveller. There is increased lethargy and tiredness. This effect is greater in travellers who have cardiac and/or lung conditions and/or whose haemoglobin is reduced (anaemia).
People who routinely go to sleep at the same time are more likely to get jet lag. This explains why jet lag is much less common in babies and children who go to sleep at any time and are better able to adjust to the new time zone.
The commonest symptoms of jet lag are a disturbed sleep pattern and decreased performance. One may not be able to sleep at the same time as the departure site or one may get up earlier than expected. If the time difference is about 12 hours, one may be awake at night and sleepy during day time. This commonly leads to a feeling of lethargy and tiredness.
Other symptoms may include gastrointestinal disorders (loss of appetite, indigestion, nausea, altered bowel habits), loss of concentration, memory lapses, headache, irritability, anxiety and a general feeling of being unwell.
There is no agreement yet for the standardisation of the symptoms of jet lag, making it difficult to compare studies. The symptoms of jet lag usually last a few days depending on how rapidly the body adjusts to the time zone at the destination.
The symptoms are worse when travelling eastwards as compared to travelling westwards. When travelling westwards, time is gained. When travelling eastwards, time is lost. The body is more comfortable with less sleep than when forced to sleep when one is not yet ready to sleep. The body's usual rate of adjustment is 1.5 hours per day after an eastward flight and one hour per day when the flight is in a westward direction.
The likelihood of jet lag and its severity are influenced by insufficient fluid intake (dehydration), alcohol intake, insufficient sleep and stress. There is much individual variation in the symptoms, which severity depends on the number of time zones crossed and the distance travelled. Most people experience the symptoms after they have crossed at least 3 time zones. However, there are others who even experience symptoms even when the journeys are shorter.
Measures to Minimise
There are several measures that can be taken to minimise the likelihood of jet lag and its severity, such as adjusting the body's body clock towards that at the destination site. This involves staying awake when it is daylight and sleeping when it is night at the destination after flying westwards and staying awake but avoiding bright light in the morning and getting outdoors in the afternoon after flying eastwards.
The measures that can be taken prior to travelling include :
* Getting sufficient sleep as jet lag is worsened if one has had enough sleep.
* Maintaining a sensible bed time schedule. The changing of the sleep schedule a few days before travelling is helpful such as getting to bed later, if travelling westwards and getting to bed earlier, if travelling eastwards.
* Avoiding stress as it worsens jet lag.
* Plan the arrival at the destination ahead of time for important events at the destination.
The measures that can be taken during the flight include :
# Maintaining adequate hydration by drinking plenty of fluids.
# Avoiding alcohol and caffeine as it aggravates jet lag.
# Setting the watch time to that at the destination helps in a more rapid adjustment to the new time zone.
# Sleeping at times which are appropriate for sleep at the destination.
The measures that can be taken after arrival include:
* Getting into the appropriate routine at the new time zone as soon as possible such as eating and sleeping at the appropriate time in the destination and not that at the departure site.
* Spending time outdoors as natural light helps in the body clock's adjustment.
* Continue exercising at the destination but avoid exercising in late evening as it can keep one awake.
Melatonin is a hormone released by the body's pineal gland in the evening that reminds the brain that it is time to sleep soon.
There is a misconception that melatonin induces sleep. It does not. What it does is that it acts as regulator switch that moves the body clock forward or backward depending on when it is taken. If melatonin is taken when darkness starts, it reminds the brain that it is time to sleep. If taken on waking, the sleep phase is prolonged.
The effectiveness of melatonin is currently not conclusive. However, a review reported that 2mg to 5mg of melatonin taken at bedtime after arrival is effective and it may be useful to continue using it for the next 2 to 4 days with the general measures described previously.
The adverse effects of melatonin have not been studied rigorously. However, it has been reported that there has been harm in epileptics and interactions with blood thinning medicines (anti-coagulants). It would be prudent to consult your doctor about jet lag remedies.
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