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The science of sleep

April 10, 2013

Packed LunchSitting cross-legged on the artificial grass with lunch in hand, surrounded by tropical ferns and the sounds of running water and birds, it all seemed like a bit of a dreamscape. So it would seem the Barbican’s conservatory room was a fitting location for a Packed Lunch talk at Wonder season with Dr Katharina Wulff, of the University of Oxford, about sleep and body clocks. Our host was Radio 4’s Claudia Hammond, who kicked off the session by quizzing our expert on a key point…How do you study sleep patterns?

Sleep cycles are measured over a six-week period to get a good picture of the average pattern, and so the odd sleepless night won’t skew the results too much. Researchers use a wristwatch-like device which measures movement of sleepers, the same basic principle as the wristbands runners and walkers wear to count their steps. These devices can tell researchers like Wulff how much someone moves during their sleep, at what time and for how long, and it even contains a sensor to detect light disturbances as well. The data collected is combined with old fashioned pen and paper in the form of a diary, where the sleepy subject meticulously notes down when they go to bed, wake up, and how much shut-eye they managed to get.

What dictates our sleep cycles?

We all have an internal rhythm which dictates when we should be awake and when we need to sleep, this is our inbuilt circadian rhythm (from the Latin ‘circa’ and ‘diem’ meaning ‘around a day’) and is calibrated to around 24-hours. The ‘master clock’ controlling this is a structure made up of around 20,000 neurons called the SCN (Suprachiasmatic Nuclei), in the hypothalamus of the brain. The cellular cogs of this clock are underpinned by genetic mechanisms, which determine the length of periodicity (wakefulness).

We have evolved to be active during daylight hours, and so our machinery needs to keep track of the changing light of our environment. Melatonin, a hormone produced by the brain’s pineal gland, is our natural sensor for the changeover from day to night and even tunes us into the seasons as the daylight cycle alters. Its production is hindered by light, but it ramps up as the light fades with production in full swing at night. “It sends a signal to other parts of the body which also need to know whether it’s day or night,” explains Wulff.

Larks and owls

There is variability from person to person and whether you are an early riser (a ‘lark’) or usually burn the midnight oil (an ‘owl’), your preference is largely down to the genetic cards you’ve been dealt. Individual preferences can be measured with simple questionnaires, and checked against the person’s individual cycle of slight fluctuations in body temperature. Although there are extremes, most people will tend to fall somewhere in the middle.

Sleep disturbances and mental health

People who suffer from mental health problems often have disturbances to their sleep patterns and circadian rhythm, although it’s unclear whether these disturbances are a direct cause or a consequence. Dr Wulff spoke of how she got involved in the field of research, explaining: “we wanted to find out what that impact actually is”. There is evidence that in conditions such as bipolar or mania, sleep disturbances can come before episodes. By identifying and addressing the sleep problem, we might be able to intervene and prevent mental health issues.

City life may have an impact on sleep cycles too. Our constant on-the-go lifestyle can mean we that work later hours and sacrifice sleep to hit deadlines. So should we be wary of bright lights and computer screens late at night? Well, depending on the intensity and type of light, it can have an effect and even suppress your melatonin production, shifting your clock later and later. The same is true for the socialites among us, if frequent late nights aren’t countered by a later wake up time (wishful thinking for most) then this can result in ‘social jet lag’, where sleep debt accumulates and your body clock is in constant transition and struggles to adjust. We do have a buffer to help us cope in the short term, but prolonged lack of sleep can lead to deterioration in mental ability and mood.

Time for bed

But if all of this talk of sleep is making you drowsy, and you’re worried you’re not getting enough shut-eye, don’t plan. Contrary to what you may have heard, setting yourself a nightly deadline for drifting off may not be the best thing for you. Planning a rigid time can actually exert mild psychological pressure. Wulff advises you just need to relax so “read a couple of pages of a book to just calm down”, and reduce light levels. Now, lights out!

Packed Lunch is a regular series of free lunchtime talks at Wellcome Collection in London. Visit the Wellcome Collection website to find out what’s coming up or stream/download podcasts of previous talks.

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