Many of us don't get enough sleep, and it's affecting our health. So what can we do about it? Dr Malcolm von Schantz, Reader in Molecular Neurobiology at the University of Surrey, explains.
Why do we sleep?
A very good question. One of the towering figures of sleep research, William Dement, who founded the world's first sleep laboratory at Stanford University, answered 'As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy'.
How much sleep do we need?
Simply put, we sleep as much as we need, and then we wake up. This need is greatest in newborn babies, who need to sleep some 15 hours a day. The amount we need gradually decreases until the end of our teens, when it stabilises at, on average, about eight hours a night. But like most biological measures, there is considerable variability around the mean. Some people need more or less sleep than others.
What happens if we don't sleep?
What we do know is that not getting any sleep at all would ultimately be fatal, and if we don't get enough sleep, it affects our health negatively in the long term. In the short term, sleep deprivation is bad for our cognitive abilities, but it doesn't make us drop dead. And of course, not getting any sleep at all during a night is quite exceptional. But chronic sleep deprivation is getting increasingly common. It has been reported that 50 years, ago, three per cent of working Americans slept less than six hours a night. Today, this figure has risen to 30 per cent.
But just as when we are deprived of an essential nutrient, the effects of not getting enough sleep will eventually creep up on us. Chronic sleep deprivation has been reported to be associated with greater mortality via a large number of negative health outcomes, including obesity, diabetes, and cardiovascular disease.
What could mediate the effects of sleep deprivation?
Here at the University of Surrey, we studied volunteers who were given the opportunity to sleep for as much as they could for one week, and during another week were only allowed to sleep for six hours a night. We then compared the gene expression profiles in their white blood cells over 24 hours during these conditions. This involved measuring the activity of thousands of genes in the white blood cells, to create a picture of the body's reaction.
We found quite profound effects of chronic sleep deprivation. We saw an increase in the activity of genes that form part of an ancient programme of gene expression that is triggered by very stressful events. Its function is believed to prepare for the injury that would have been likely to follow such extreme stress in our ancestors, so that the body is ready to start wound healing and infection control.
But today, such stress rarely leads to actual physical injury. As a result, the body finds itself with a proinflammatory response, but no wound to heal. This could contribute to the well-known negative effects of stress, and of sleep deprivation, on cardiovascular health.
Why are do people get less sleep today than 50 years ago?
Over the last century, the availability of electricity has increased dramatically worldwide, at the same time as the cost has gone down. Until very recently, our activity patterns were dictated by the light-dark cycle created by our planet’s rotation around its own axis. To our ancestors, midnight really was the middle of the night. Today, we are able to extend the period of light, and have the equipment to keep ourselves occupied way beyond the time the sun sets. As a result, many of us aren’t even in bed by midnight. But most of us still have to get up early in the morning. Something has to give, and that something is sleep. Early to bed, early to rise works. Late to bed, late to rise would work as well. But the problem is that for most of us, that is not a feasible option.
So much else has changed in our society — diet, physical activity, external stress. How can we be sure of what is specifically caused by changes in sleep and in light exposure?
Indeed, that is the tricky part. Industrialisation has happened so quickly and so thoroughly that, in most parts of the world, it is too late to compare before and after. Our own approach has been to focus on a small town in Brazil called Baependi. Our colleagues at Incor, the cardiovascular institute of the University of São Paulo Medical School, began a study in this town almost a decade ago. This means that we already have a very detailed picture of factors relevant to cardiovascular health in this town, and they have recently started collecting information related to sleep, biological rhythms, and life exposure as well. Our project, together with colleagues in São Paulo and the University of Chicago, is now beginning to piece these factors together.
What makes this town so unique and interesting?
First of all, the people — the citizens of Baependi have been wonderfully cooperative and generous with their time during all the years of the study. Second, there are some very interesting features here that are typical for Brazil — the racial mixture, and the traditional diet. Third, the fact that the lifestyle in this town is in many ways still very traditional.
What have you found so far?
Although almost everybody in Baependi has electricity and television, their preferred bed and rise times are much earlier than what you would find in larger metropoles such as São Paulo and London — up to two hours on average, in the rural part. This means that in some ways, we are looking at people whose lifestyle is more similar to that of earlier generations. Why is a little bit of a mystery — they do have electricity, and they do have television. The most important factor at play here, we think, is light exposure. Many of these people have outdoor jobs, which would expose them to natural light. In fact, what we are seeing in Baependi reminds me a lot about a recent report by Ken Wright and his team at the University of Colorado. They took a group of city dwellers on a camping trip, with the sun as the only light source. What they found is that the rise and bed times, and the biological rhythms of these individuals, changed to a set point that was two hours earlier.
So should we all get out in the daylight more?
We certainly should make sure to maximise our light exposure in the morning. Unlike our visual system, our body clock is only sensitive to light at specific time windows. Light in the morning will advance our internal clock, and light in the late evening will delay it. Because most of us have an internal clock that it set to a day length of slightly more than 24 hours, we need to continuously advance our clock. Walking to work or to the railway station in the morning is very helpful for this — keeping the lights on in the late evening is not.
Finally, to your research project — what are you planning to do over the next two years?
We are really thrilled to have received the Global Innovation Initiative award from the British Council, and at almost the same time, we received another grant from CNPq, the federal Brazilian research council. This means that we will have two postdoctoral research fellows working together on the same project — one in the UK, and one in Brazil. This is a really new way of working for us, and I am enormously excited about it, and also about the project itself. We will be collecting actual measurements of people's activity patterns and light exposure over one week. We are also planning to do sleep recordings in people's homes. We will be able to relate all of these data to different people's physical and mental well-being. So we think that by studying this little town in Brazil in such great detail, we will be able to learn a lot about sleep and health that will apply to people everywhere.
Dr Malcolm von Schantz's team at the University of Surrey won a grant through the Global Innovation Initiative. He's working with the University of São Paulo Medical School and the University of Chicago to do research into sleep and biological rhythms, and how they interact with our health.