Santa Claus is coming to town – all towns, really – which means he'll be on a very long flight around the globe that ends with lots of toys for kids, but a terrible case of jet lag for him. Think about it: he gets on his sleigh, flies all night with no shut eye, and scarfs down milk and cookies along the way. Most sleep experts would agree it's a recipe for disaster.
Let's break it down. With all the time zones, let’s assume he's going for 24 hours in constant darkness, with lots of climbs and descents. He gets home, crashes hard because he’s so exhausted, but still rises early. His appetite is out of whack, maybe has a headache and spends some time in the bathroom. That next night, he’s in bed around 8 p.m. but wide awake at 2 a.m. It likely takes him days to get back to normal.
His long flight threw off the master “clock” in his brain that controls the many mini clocks in his body.
“When we fly across many time zones, we force our bodies to perform daily tasks at a time different from the one our bodies are used to,” said Georgios Paschos, PhD, a research assistant professor in the department of Systems Pharmacology and Translational Therapeutics. “By forcing our body to stay awake when it is used to sleeping, feed at a time it is used to fasting, and be active at a time that it is used to being sedentary, we cause irregularities in a variety of body functions, such as neuronal firing, digestion, blood circulation, and hormone secretion.”
It’s those irregularities that cause problems in the ensuing days and potentially even months or years later.
Poor Santa. “He should have the worst case of jet lag ever,” said Mitchell Lazar, MD, PhD, director of Penn’s Institute for Diabetes, Obesity, and Metabolism, who studies metabolism and the body’s circadian clocks.
There are the short-term problems that blow over after a few days: tiredness and fatigue, trouble concentrating, bowel issues, and a reduced appetite. But then there are the more serious, long-term issues many studies have associated with chronic jet lag, like cancer and heart disease. This refers to the people who fly a lot -- once a month from California to Tokyo, or every week from Los Angeles to New York, for instance.
One study in the Journal of Neuroscience found that frequent flyers had significantly higher levels of salivary cortisol, a hormone that’s been linked to cognitive deficits. Those who had been on the job longer scored lower on memory tests compared to short-timers, the researchers reported. Another study from the University of California, Berkeley, that subjected hamsters to continued disruptions of light to mimic jet lag, found that those critters had lasting learning and memory problems.
Many of the body’s “clock genes” may become out of sync or shut down because of chronic jet lag, which over time could lead to disease.
“Our bodies’ biological clocks are encoded in our genes,” Lazar said. “It’s a series of gears tuned to the 24-hour cycle, where the gears are molecules, and the molecules interact with each with other, the same way that the gears of a clock interact with each other. Muck up that system with something like flying or night shift work enough times, and those gears can go awry.”
Researchers at the University of Kentucky removed several of these “clock” genes – Bmal1, Rev-erbα, and Per – from the heart cells of mice, and found that they had abnormal electrocardiography results and were more susceptible to abnormal heart rhythms, according to a study in the Journal of Clinical Investigation last year.
A mouse study in PLOS Genetics from this past September found a link between an increase in Arntl2, a gene known to regulate the body clock, from continued sleep disruption and estrogen receptor-negative breast cancers. Researchers at Baylor College of Medicine reported in Cancer Cell in early December that chronic jet lag may also increase a frequent flyer’s risk of liver cancer.
Mice subjected to jet lag-like conditions lost control over normal liver metabolism because of a disruption to two well-studied receptors known as FXR and CAR, which help regulate bile acid in the body. Jet-lagged mice were more likely to have increased levels of the bile acid and liver cancer.
“The study extends on the findings of previous ones suggesting that chronic disruption of circadian rhythms increases the risk for cancer,” Paschos said. “In this context, it is valid to suggest that it may be contributing to the increase in liver cancer rates we’ve been seeing.”
It’s debatable as to whether Santa suffers from chronic jet lag, given the fact that he only makes the big trip once a year, but just look at that belly. Spreading Christmas joy since the beginning of time has left him fat (though jolly), and it’s likely not just from all the snacks. Disturbances of circadian rhythms have long been linked to obesity, too.
Or perhaps Santa is built to withstand the jet lag. Some people have genetic mutations that give them abnormal sleeping habits with little issue and an edge when it comes to getting back on track after flying.
“They’re called night owls and morning larks, where it’s natural for them to wake up at three in the morning and go to bed at six or seven at night or stay up all night and sleep during the day,” Lazar said. “Turns out, in many cases, it’s due to a genetic change in one of the ’clock gear’ proteins, and it runs in families.”
For everyone else, there are remedies to stave off jet lag. One doesn’t need to look for too long on the internet to find them during the holiday season either. Experts have recommended melatonin, fasting, blasts of thin air, and even flashes of light.
“I think one can try to ameliorate the risks by staying as close as possible to the same 24-hour cycle they are used to,” Lazar said. “There are parts that are biological you can’t control, but there are psychological aspects that you can take some steps to help. Mainly, be careful about what and when you eat.”
He’s talking to you, Santa.