Russell Foster thinks you should get more shut-eye – and he should know. A professor of circadian neuroscience at the University of Oxford, Foster has spent his life studying the human body clock and trying to answer the question: What happens during the more than one-third of our lives that we spend sleeping? The short answer: a lot more than you think.
Every living thing is regulated by a roughly 24-hour internal clock, which keeps ticking even when there is no light around to signal what time it is. But here’s where things get tricky. There isn’t just one body clock – groups of molecules have their own individual circadian rhythms that are regulated by a single master timekeeper in the brain, known as the suprachiasmatic nucleus, or SCN. One of the more important discoveries that Foster’s research group has made is that specialized light-sensitive cells in the eye feed information to the brain and help regulate the SCN. The discovery has helped scientists understand not only how light affects whether we feel sleepy or alert, but also why crossing time zones gives us jet lag. They’ve also found links between severe mental illness and out-of-kilter body clocks, suggesting that one way to help such sufferers is simply to help them reset those clocks.
But perhaps what Russell is best known for, particularly after giving a popular TED Talk in June, is his insistence that people should prioritize sleep more than they do, especially in an increasingly connected world where go-getters earn bragging rights by talking about how little time they have to rest. The Financialist recently caught up with Foster to talk about the science of sleep, our daily rhythms and jet lag.
The Financialist: If sleep is such a fundamental part of our biology, why do you think scientists have paid it so little attention over the years?
Russell Foster: It’s partly because we have only recently developed the tools to study the sleeping brain more easily. We’ve learned that during sleep, we consolidate our daily experiences in the form of memories. But the brain also plays with that information, coming up with novel solutions to complex problems. Despite these scientific discoveries, however, people still assume that when they are asleep, their brains are simply shut down, doing nothing.
TF: What happens when you don’t get enough sleep?
RF: The first thing tired people tend to do is become much more impulsive and less reflective. In other words, they can’t think properly. With too little sleep, people start driving the waking day with stimulants like caffeine. As a result of that, when they try to sleep at the end of the day, they often can’t. At that point, they may take alcohol or sleeping tablets to induce sedation, which doesn’t allow the most important biological process of sleep to take place. Just because you aren’t conscious doesn’t mean you’re getting all the benefits of real sleep.
Interpersonal skills also fall apart with too little sleep. Tired, sleepy people tend not to be empathetic. With sustained sleep deprivation, too, people can get depressed. After all, how does your body override the urge to sleep? It activates the stress axis. Sustained stress also suppresses the immune system, leaving you more susceptible to infection, Type-2 diabetes, cardiovascular disease and even cancer – a finding for which there is good evidence in studies of nurses who work the night shift. A lack of sleep also increases your risk of weight gain and obesity. Sleepy people have more ghrelin, the so-called “hunger hormone,” so they’re more likely to eat carbs – particularly sugars. And it only gets worse: the older you get, the more vulnerable you are to the health impacts of sleep deprivation.
TF: Are there any lucky souls who really don’t need much sleep?
RF: There is a lot of individual variation in how much sleep people need. But sometimes, people who claim they don’t need much sleep are simply too tired to discern that they’re sleepy! This has been shown in nighttime taxi drivers, who claim not to be tired when they’re actually suffering the effects of massive sleep loss. It’s a critical issue – night-shift workers are often impaired without knowing it.
TF: What about when people sleep? Is there an optimal time to go to bed and wake up?
People’s individual sleep cycles vary. If I were trying to figure out someone’s individual body clock timing, I would ask: “What happens on your free days? What time do you get up without an alarm clock? Does your sleep pattern change markedly when you’re on vacation?” Many people change their sleep habits on holiday, and the schedule they follow at those times is a better reflection of their true individual sleep-wake cycle.
Sleep patterns also change as we age. Once we get past the age of 10, we tend to go to bed later and later. We start becoming night owls in the teen years, though the average female will never stay up as late as the average male. Then there’s a slow reversal, so that by the time you reach 55, you are back to the wake-and-sleep times that you experienced just before puberty – around age 12. Some of these changes seem to be driven by sex hormones, which rise and fall over time. But in general, younger people are late night types, and older people are morning types.
TF: Let’s talk about jet lag. What happens in your brain when you cross time zones?
The human body clock works on a cycle of about 24.5 hours, so we need to align the internal clock to the external world by about half an hour each day. Light is critical to that process. If a person went into a cave that had constant darkness and temperature, he or she would still fall into a regular rhythm of sleeping and waking, but would get up and go to bed slightly later each day because of that extra half-hour in the internal cycle.
The classic mismatch between our internal clock and external time is called jet lag. We eventually get over jet lag as the light in a new time zone re-sets our internal clocks. But the reason we feel so awful in the meantime is that during the adjustment, all the different clocks in the body – the ones in the brain, liver and stomach, for example – are slightly out of sync. They all realign eventually, but it takes about a day for every time zone you cross.
If you’re traveling west, it’s easier: You can adapt faster to an expanding day. Trying to adapt to a contracting day when you go east is more difficult. So here’s my simple advice: Seek out morning light whenever you can when you’re traveling west. But if you’re traveling more than six or seven time zones east, you need to avoid morning light at your destination for three days and seek out afternoon light instead.
TF: Do common remedies for jet lag, like melatonin, do any good?
RF: Lots of people take melatonin, but its actual impact on our biology is poorly understood. Melatonin is a biological marker of nighttime, meaning it is produced when it’s dark. So, it could be that sending your body this “dark signal” in pill form augments the light signal detected by the eyes and speeds up the resetting effects light has on your body clocks. But we haven’t shown that definitively yet. One thing we do know is that about 70 percent of people will fall asleep more quickly if they take 3 milligrams of melatonin, which makes it easier to sleep in a new time zone. Of course, one should always talk to a doctor before doing that.
TF: Some of your recent work seems to suggest there could one day be a more effective pill for jet lag. Tell us about that.
RF: We published some of our recent findings in the journal “Cell” a month ago. We were trying to figure out why it takes so long to adjust to a new light-dark cycle. Why, for example, does it take an extra day to recover for each time zone crossed – why doesn’t your body make a more immediate adjustment? In the paper, we described a new pathway that limits the effects of light on the molecular clock. When we greatly reduced the amount of a key protein in that pathway in a group of mice and shifted the light cycle they were exposed to by six hours, their internal clocks adapted after a day, rather than six days. Since the human clock is very similar to the mouse clock, this pathway could be used to develop pharmacological agents that speed up the resetting process. We’re already working on drugs that can shift the internal clock in humans – and not just for jetlag. Drugs like these have the potential to help people with poorly adjusted inner clocks, a phenomenon we find in many conditions, including mental illnesses such as schizophrenia.
Q: What do you want people to know about sleep that they don’t already know?
As a society, we’re not going to put the 24/7 genie back in the lamp and start living without electric lights. But people should know that sleeping less makes them more susceptible to health problems. For example, our ability to process food, particularly glucose and fats, is not as effective at night. So, we know that people who work night shift are susceptible to obesity, and that tendency is made worse by the type of food that’s usually available during those shifts. You can’t do much about your work schedule, but night-shift workers could adjust their eating habits by sticking to small, easy-to-digest portions of foods with relatively high protein, low carbs and low fat. Something calming and easy for the system to process.
Most of all, I want people to think about sleep more seriously. We spend around 36 percent of our lives asleep. It’s our single most important behavior, and a lot of really important stuff is going on in the brain while we sleep. If you make getting enough sleep a priority, you’ll perform better at work and in your relationships, and you will be less likely to get sick.
Q: So the bragging rights of pulling all-nighters aren’t all they’re cracked up to be?
Exactly. The idea that sleep is a waste of time is relatively recent. If you look at the early scientific literature – even into the 19th century – people embraced sleep. The turning point came with the invention of the electric light bulb. Thomas Edison said sleep was a criminal waste of time and a throwback to our cave days, and that attitude persists today. As a species, we are incredibly arrogant, but we can’t abandon our embedded biology. Margaret Thatcher famously said sleep is for wimps. She was wrong.
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