Travel fatigue affects many people, but there are ways to minimise the effects, writes Dr Giles Warrington.
Many Irish families and individuals will soon be heading abroad for their summer vacation. Through the emergence of budget airlines, air travel has become more accessible, with more of us travelling to foreign destinations than ever. For many, the travel experience will require packing up the family, spending extended time queuing and waiting in crowded airports, not to mention the dreaded flight delays.
Travel is associated with a number of negative symptoms, collectively termed "travel fatigue". These negative effects (which include fatigue, disorientation, headaches and general travel weariness) are associated with a disruption to normal routine and the stresses associated with travel. With appropriate planning and effective coping strategies, symptoms will disappear within one or two days.
Long-haul travel can result in jet lag, due to a disturbance of your body clock as a result of travelling across a number of time zones. Jet lag is generally associated with - among other things - weakness, fatigue, loss of appetite, poor concentration, headache, irritability, poor motivation/drive, reduced physical and mental performance.
Current evidence suggests that travelling in an easterly direction requires a phased advance of the body clock of eight hours (eight time zones), which would take about seven days to achieve. However, the rate of adaptation is determined by a number of factors and, as a result, some individuals may require more time to fully adapt.
Jet lag affects individuals differently, both in terms of severity and rate of recovery, which is determined by a number of factors: the number of times zones crossed; the direction of travel; fitness levels (individuals with higher levels of physical fitness generally adapt more rapidly); age (younger individuals are generally more flexible and have less difficulty coping with jet lag). However, contrary to this, evidence suggests that older individuals are better able to pace themselves when dealing with sleep loss.
Travel experience can also have an effect - the more you travel and the more effective your coping strategies become for dealing with jet lag, the more rapidly you are likely to adapt. Chronotypes or "morning" people tend to adjust more readily to travel in an easterly direction than "night" people, and vice versa.
Most modern commercial passenger planes typically fly at an altitude of 9,000-12,000 metres (30,000-40,000 feet) with the outside air temperature possibly reaching -55 degrees. At such altitudes, the air is very thin and the availability of oxygen to sustain normal physiological function is significantly lowered.
If you consider mountaineers climbing Mount Everest, at an elevation of 9,000 metres above sea level, they usually require specialist breathing apparatus to reach the summit. As a consequence, airline cabins are de-pressurised to an altitude equivalent to about 1,500-2,500 metres so that supplementary oxygen is not required.
Nevertheless, the lower cabin pressure compared with sea level lowers the oxygen saturation in the blood and may lead to some degree of discomfort for the frail, and particularly those with cardiovascular disease.
The circulating air within the plane is also generally very dry and may lead to significant fluid loss, particularly from the respiratory tract, which may cause a dry mouth and throat as well as dehydration.
The air circulating in modern planes is usually a combination of fresh and re-circulated air, which is normally filtered. It is suggested that the risk of picking up an airborne infection during a flight is probably no different to other confined public areas such as offices, trains and cinemas.
The economy seating in most planes is usually cramped with minimal leg room. Prolonged periods of remaining seated and immobile in a confined position can lead to swelling in the ankles and lower legs, caused by the build-up of excessive fluid in the tissue spaces.
Of even greater concern is the prevalence of deep vein thrombosis (DVT), commonly referred to as "economy-class syndrome". DVT is caused by the formation of a blood clot within a blood vessel and generally occurs in the legs, but may also be found in other parts of the body.
Evidence would suggest that the risk of DVT due to immobilisation approximately doubles after a long-haul flight of greater than four hours. The level of risk appears to increase with the duration of flights as well as multiple flights over a short period of time and has also been linked to other risk factors such as genetics, obesity, extremes of height, diabetes and age.
Nevertheless, the absolute risk is still low and has been shown to be about one case in 6,000 individuals. For those deemed to be at risk, the use of compression stockings during travel is commonly recommended.
Travel - in particular long-haul travel - by its very nature can be extremely stressful and tiring. Effective preparation is the key to making sure that the disruption of travel is minimal and that the transition to local time of destination is as smooth as possible - this requires planning and preparation.
• Dr Giles Warrington is a sports and exercise physiologist and lecturer in the school of Health and Human Performance at Dublin City University