Have you ever suffered jet lag after travelling long distance by aeroplane? Have you ever found that as well as a disrupted sleeping and eating pattern, your brain isn’t quite as switched on as usual? Does it sometimes take a day or two for you to adjust to your new time zone? Jet lag is a well-described phenomenon, which affects people to varying degrees. It has also been recognised that flying across time zones going east is more likely to disrupt our body’s internal clock than flying west.
Up until now though, there has not been any information available as to what effects if any long distance air-travel has on how our brain works in the longer term.
The results of a new study from Berkeley University of California published in PLoS ONE, have revealed some surprising findings.
In this study, female Syrian hamsters were subjected to the equivalent of flying from New York to Paris (that’s crossing six time zones) twice a week for four weeks. The hamsters’ performance for learning and memory was assessed in the last two weeks of the simulated jet lag and for a month afterwards.
Not surprisingly the hamsters had difficulty performing simple learning tasks in the two-week period of long distance flying. However what was of surprise to the researchers was that these deficits lasted for a month after the hamsters returned to a regular day/night schedule.
More specifically changes were found in the area of the brain called the hippocampus, a key brain area for learning and memory. It was found that on a cellular level the number of new brain cells being formed there were only half the expected number. The main issue here was that fewer new brain cells were surviving to maturity. It was also shown that the effect was not just through increased cortisol levels as part of the stress response.
For infrequent air travellers, jet lag is a minor annoyance that settles in a few days as the body’s internal clock resets itself. However for those having to use air travel, which requires crossing time zones frequently, and similarly for shift workers, the long-term impact can manifest itself in learning and memory problems, decreased reaction times, and an increase in the incidence of diabetes, hypertension, heart disease, cancer and even reduced fertility.
Why hamsters were chosen for this study was because apparently they have very precise body rhythms. The females ovulate every 96 hours within a variability of just a few minutes. (Syrian hamsters are widely kept as pets and their name is derived from the fact they were first discovered in Syria in 1839.) I’m glad though, not to be a female hamster; the thought of having to go through all that PMT would be hideous.
The World Health Organisation has listed shift work as a carcinogen. In the light of these findings, should long distance air travel be classified similarly?
The current recommendation to avoid jet lag being too much of a nuisance is to allow one day of recovery for every one-hour time zone shift. So flying from Perth to Sydney I would need to allow three days for my brain to recover. Which, as I don’t do this very often, is not really an issue. But if you are having to flying across Australia regularly or are working as air- crew the implications would appear to be far more significant.
Ref: University of California - Berkeley (2010, November 25). Jet-lagged and forgetful? It's no coincidence: Memory, learning problems persist long after periods of jet lag. Science Daily.