by Mike Cadogan, MB ChB

Crossing multiple time zones can produce a constellation of symptoms known as jet lag.

Jet lag is most noticeable in the first 24-48 hours following travel and can last for up to 5 days before individuals return to normal functioning. Symptoms are closely affected by both the length and direction of travel. Symptoms include: reduced alertness, night-time insomnia, loss of appetite, depressed mood, poor psychomotor coordination and reduced cognitive skills. Work capacity and peak power are also reduced.

Factors affecting poor recovery from travel include

• A lack of sleep or very restless sleep during flight
• Dehydration from dry environment of the aeroplane cabin (contribute to tachycardia and headaches)
• Number of time zones crossed
• Direction of travel (westward travel is easier to tolerate than eastward)
• Fitness levels (fitter people adapt better after travel)
• Personality (outgoing types appear to adjust quicker)

One of the major challenges of travelling with elite athletes is to minimise the negative symptoms associated with international travel in as natural a way as possible. To best refine a travel management plan it is first prudent to understand the pathophysiology of the sleep/wake cycle.

Daily circadian variation exists in elite athletes with peak performance occurring in the afternoon and early evening with improved flexibility, reaction time, strength and mood at this time of day. International travel disturbs these circadian rhythms and can have a negative impact on performance.

Melatonin

Synthesis of melatonin by the pineal gland is inhibited by light and stimulated by darkness.

Melatonin has been dubbed the “hormone of darkness.” Secretion of melatonin commences each evening as the Dim-Light Melatonin Onset (DLMO), peaks in the middle of the night, and gradually falls during the second half of the night, with normal variations in timing according to an individual’s chronotype.

Increases in the level of melatonin causes the body to feel less alert and has an important role in inducing sleep and producing the symptoms of jet lag.

Dysregulation of melatonin secretion and circadian rhythm disturbances are thought to be the common links which underlie jet lag and affective mood disorders. As a result of its regulatory effects on the circadian system, it follows that melatonin may be used effectively to treat the range of symptoms that accompany transmeridian air travel.

Melatonin acts on MT(1) and MT(2) melatonin receptors located in the hypothalamic suprachiasmatic nuclei, the site of the body’s master circadian clock. Melatonin can reset disturbed circadian rhythms and promote sleep in jet lag and other circadian rhythm sleep disorders, including delayed sleep phase syndrome and shift-work disorder. Post-flight melatonin administration works efficiently in transmeridian flights across less than 7-8 times zones.

Pharmacological implications

Despite pathophysiological evidence, there is still a persisting culture of players requesting stronger sedative agents to assist in artificially creating a new time-zone sleep/wake cycle. Agents such as bezodiazepine (diazepam) and non-benzodiazepine hypnotics such as Zolpidem are still frequently prescribed to travelling elite athletes to reduce the negative symptoms of jet lag.

I am currently implementing a more evidence based approach to the management of circadian cycle disruption by administering melatonin or the newer melatonin receptor agonists. On this South African tour we are trialling the use of direct sunlight exposure for 30 minutes each morning (in addition to daily excersise regimes) and the administration of 2-4 mg doses of melatonin at normal bedtime in the setting of darkness (22:00 local time). So far the administration of melatonin has had a fantastic effect in organing an effective sleep/wake cycle for the players and has drastically reduced the administration of previously abused agents.

Ramelteon and agomelatine are melatonin receptor agonists which, compared to melatonin itself, have a longer half-life and greater affinity for melatonin receptors and consequently are thought to hold promise for treating a variety of circadian disruptions. We will trial these agents for the next international tour.

Mike Cadogan is a physician in Australia who blogs at Life in the Fast Lane.

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