Jet lag is an unpleasant feeling of generally having lost your rhythm, and feeling tired or confused. It comes on when a traveler crosses several time zones, especially from west to east. It is more frequent in people over 60 years, and with very long flights. Its symptoms vary, but are due to the disruption of the body’s natural patterns of activity.
Biological or Circadian rhythms are 24-hour patterns of bodily activity. They regulate vital functions, including digestion, sleep, memory, heart rate and blood pressure. These depend upon the settings of the biological clock, which is located in the suprachiasmatic nucleus of the hypothalamus, deep in the brain.
This part of the brain is also the part which receives light signals from the retina, in the eyes. Thus it regulates the diurnal variation in the secretion of melatonin and other brain chemicals. These in turn set the rhythm for the daily patterns of nerve stimulation and endocrine secretion, which finally control all the other body processes.
Symptoms of jet lag
When you have jet lag, you may:
- Find it difficult to get to sleep
- Experience very light or fitful sleep, with frequent awakenings
- Feel sleepy during the day
- Be less alert than usual, and find it hard to concentrate
- Perform normal tasks less well than usual
- Feel tired and irritable
- Experience memory lapses
- Show poor judgment
- Feel apathetic or depressed, with loss of interest in routine things
- Have an upset stomach
- Have disturbed bladder and bowel routines
Does jet lag really matter?
With frequent fliers who travel long miles by air, the disturbances can become permanent. The sequelae of jet lag include:
- Alterations in menstrual cycles
- Altered memory and cognition, or mental processing
- Atrophy of the temporal lobe
- Cardiovascular disease, including stroke and heart disease, diabetes, and similar metabolic illnesses, resulting from eating at times which do not match the body’s ‘home time’ digestive rhythms
- Higher chances of cancer and, in mouse research, reduced survival periods after the diagnosis of cancer
Factors affecting the occurrence of jet lag
Not all people experience jet lag to the same degree or for the same duration. The factors which determine the severity of jet lag may include:
- Individual constitution, which determines the ability of the circadian clock to advance or delay its phase in keeping with the external environment.
- Number of time zones crossed – when more than two time zones are crossed, symptoms usually occur.
- Age – the ability of the biological clock to shift rapidly decreases with age, so that those over 60 years, generally take longer to overcome jet lag.
- Direction of the flight – phase advance of the biological clock takes longer than phase delay to re-entrain to the time of the destination time zone, so that symptoms take longer to resolve if a person flies east rather than west.
Significance of jet lag
Since jet lag symptoms affect a person’s peak mental, physical and emotional performance, it can cause undesirable effects which reduce athletic fitness and negative affect peak performance. Similarly, jet lag can result in impaired judgment, leading to poor decision-making and strategic skills during the recovery period, which could affect international relations. The same applies in the financial and business world. Thus the symptoms of jet lag are far from being a trivial affair.