exhausted business man with jet lag (1500 x 1000 px)

I am getting ready to take a couple of long trips in the next few weeks, and as always on such trips, I am tethered to my laptop computer, monitoring information and making business decisions. I have been doing it all throughout my working years and thought that I was a master at it. I was proud of being awake and alert during interminable business meetings overseas, and making important decisions with aplomb, running on gallons of caffeine, adrenaline and willpower.

Until I realized that I was not always as smart as I thought. Countless times I had to modify, or even rescind decisions that had seemed pretty astute at the time. Why did I dismiss that suggestion out of hand? Did I really listen carefully, or did I react with impatience and a dash of annoyance? And what was it that we discussed at 3 pm in London? For the life of me, I could not recall a thing.

What is this so-called ‘Clock’

Well, there are actually many clocks in the body but fortunately none of them marches to its own drummer -the are all highly coordinated.

The central clock is made up of 20,000 neurons that make up the suprachiasmatic nucleus (SCN), located in hypothalamus. If you checked the activity of these cells in the lab you’d find them cycling through approximately 24 hours cycles; 12 hours of light-related neuronal activity and 12 hours of dark-related activity. But our days are rarely neatly divided into 12 hour periods. So how does the SCN adjust to reflect this reality?

The main modifier of the neurons in the SCN is light. There is a specially dedicated neuronal pathway, going from the retina to the SCN, that transmits the status of external light. This in turn regulates certain genes, known as clock genes, that determine the activity of the cells. There are other influences that modify the central clock, such as temperature and mealtime.

You don’t have to be a scientist to know that jet lag doesn’t affect your sleep pattern only. It wreaks havoc with your appetite, your bowel function, your exercise performance, etc. This is because every organ, every tissue, every cell, have their own internal time keepers. This could be a recipe for disaster if each of those clocks asserted their independence and marched to their own drummer. So how was such a scenario of biological chaos averted? Through central control. The SCN takes the information on the lengths of the day and night from the retina, interprets it, and passes it on to the pineal gland, a tiny structure shaped like a pine cone and located on top of the thalamus. In response, the pineal secretes the hormone melatonin. Secretion of melatonin peaks at night and ebbs during the day and its presence provides information about night-length. This hormone reaches all the cells in the body through the circulation, and so causes the “slave” peripheral timekeepers to synchronize with the “master” timekeeper in the brain.


You can fool yourself, but not your biological clock

There is a surfeit of studies showing that travel across time zones plays havoc with your health. It has been documented that people who have to frequently change their sleep patterns suffer a higher rate of hypertension, atherosclerosis, diabetes and cancer.

What about the brain? Your circadian rhythm gets out of synch, you are tired in the morning, perking up at bedtime. And even a ton of coffee is not going to sharpen your performance much. For neurobiologists, it has been “obvious” that disruption of the biological clock is at fault. But how? What’s the mechanism underlying this scourge of all road warriors and night shift workers?

An article in Wired magazine (“Jet lag makes you stupid”) reports on work presented November 15, 2010, at the annual Society for Neuroscience meeting. Erin Gibson of UC Berkeley and her colleagues subjected hamsters to jet lag by advancing their day and night schedule by six hours every three days for nearly a month. As Gibson put it, “It would be like a flight from New York to Paris every three days”. The hamsters’ total sleep amount didn’t change, but the hours spent awake and asleep were completely unrelated to the external environment. I have in mind one guest of ours from the East Coast who would wake up and start calling people 3 AM California time.

What the researchers found was the anatomical explanation for jet lag: it decreases the numbers of new neurons being born in the hippocampus by about 50 percent. Now, when it comes to memory the hippocampus is the central depot, where auditory (sound), visual, olfactory (smell) and tactile (touch) sensations are organized, packaged, and sent back to various storage areas in the brain, to be retrieved by it when called upon.

What about learning ability? We know that memory is an essential part of learning. Indeed, the jet-lagged hamsters were worse at learning which of two chambers contained a desirable running wheel. Even after 28 days of a back-to-normal schedule, the formerly jet-lagged hamsters still showed learning and memory problems. The mismatch between the internal body clock and the external environment “is having a long-term effect on learning and memory,” Gibson said.

So we can see now that messing with your hippocampus goes beyond unpleasant; the extent of the damage (50% reduction in new neurons!) is, well, mind boggling.

These studies are still preliminary, of course. We still don’t know how the biological clock controls all those physiological functions that are being disrupted in jet lag and night shift work. And hamsters are not humans; we still have to demonstrate the same phenomena and quantify them in human beings. Nevertheless, the study is a great step forward in understanding the impact of this unhealthy byproduct of the modern world.


Are there remedies for jet lag?

There are literally hundreds of remedies for jet lag. Adjust your circadian rhythm to your destination a few days before departure; take melatonin; eat carbohydrates; eat proteins; skip meals; keep well-hydrated; don’t drink alcohol (this one is the worst ideas I’ve come across). The fact that there are so many suggestions means that none of them is really effective.

I am sure that each one of you has his own miracle formula. Please, don’t inundate my mailbox –I’ve tried them all. Me? I just load up on sleep. I knock myself out on the flight with a sleeping pill, I take one for the night, every night until I adjust. Not perfect, definitely not “physiological” –but it works for me. Sort of.

Updated 6/4/14

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.


  1. Thanks for the sleep article Dov. It was quite timely for me as I will be traveling internationally most of the winter. I agree with you. The thing that works best for me are sleeping pills. It takes me about 3-4 days to adjust and then I stop the pills. My issue is picking up viruses in flight. Those are hard to avoid. Any ideas?

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