How the seasons change our sleep The clocks are changing and the days are getting longer. Research suggests we might want to consider what this means for our bedtime. Research suggests that humans may need more sleep during the dark winter months than they do during the summer The clocks are changing and the days are getting longer. Research suggests we might want to consider what this means for our bedtime. The arrival of spring often heralds a welcome change after the long, hard winter months. The Sun stays up for longer, the days grow warmer, the first flowers begin to bloom, and the clocks tick forward into daylight savings time to lengthen our evenings. But there is one change that is likely to be less appreciated as we move steadily towards the summer – you start to get less sleep. Many of us are familiar with the struggle to muster the energy to leave bed in the morning during the winter, choosing instead to hit the snooze button. And scientists say this isn't surprising.. This need seems to even occur in people living in cities, where artificial lights would be expected to interfere with the natural influence of daylight on our sleeping patterns. "Our study shows that even while living in an urban environment, with just artificial light, humans seasonal sleep," says Dieter Kunz, one of the study's lead authors and head of the clinic of sleep and chronomedicine at St Hedwig Hospital in Berlin, Germany. "I would expect the seasonal variations to be much higher, living outside and were only exposed to natural light," he adds., the hormone produced by the pineal gland that regulates our circadian clock, the natural sleep-wake cycle that repeats every 24 hours, and makes us feel sleepy. But the German study, which used detailed sleep recordings of 188 patients who lived in urban settings and suffered from disturbed sleeping patterns, found that even when exposed primarily to artificial lights, the participants experienced seasonal variations in REM sleep, which is directly linked to our. In fact, the participants slept an hour longer in December than in June. Their rapid eye movement sleep, which is the most active stage of sleep when we dream and our heart rate increases, was 30 minutes longer in the winter than during the summer. REM sleep is regulated by the circadian clock, "so the fact that it goes in parallel with seasonality makes sense", says Kunz.The German scientists say children may benefit from an earlier bed time in the winter But Kunz's team was surprised to find that there were also seasonal changes when it came to slow wave sleep , also known as deep sleep. "We found specific changes in REM sleep and deep sleep, the two major stages in sleep, over the year. This was completely new," says Kunz.The seasonality of deep sleep "was something we did not expect," says Kunz. " deep sleep is not driven by the circadian timing system;Kunz says more research is needed to understand why we need less deep sleep in autumn than in winter. "We still have no idea what it means functionally." It is also worth noting that the study was performed on patients suffering from sleep-disturbances such as insomnia, so it will need to be repeated in a healthy population to confirm these effects are seen more widely.Neil Stanley, a sleep expert at Sleep Station, an online provider of cognitive behavioural therapy for insomnia, says it is "puzzling" that we wouldn't need more deep sleep during the winter. "Slow wave sleep is thought to be the most important because it's involved in memory, learning and optimising the immune system," says Stanley. "The perception is that we would prioritise over everything else. If you were to go without an entire night's sleep, the next night you would make up all of your missing deep sleep, and only half your missing REM sleep," he says.Exactly why our sleep changes with the seasons could be hidden in our evolutionary past, says Stanley. "We have evolved to dark-light cycles, so when we wake up on a winter's morning and it's dark, our brain is going 'I can't do anything…there's no point leaping out of bed'."Besides going to bed earlier in the winter, what other steps can we take to improve our sleep? "Get as much natural light as you can in the morning hours, so that your circadian system at least knows that the day has started," says Kunz. "It's important that before they go to school, kids spend at least 10-15 minutes outside, the sky," he adds. People can tolerate different levels of light at night, says Stanley, but recommends avoiding bright lights in the two hours before bedtime and phone screens right before going to sleep. But a good night's sleep is also dependent upon temperature. Our bodies require a skin temperature of between 31-35C , something we can control relatively easily with central heating in the modern world. In the summer, when higher temperatures are more common, this can be harder to control, particularly during heatwaves. According to a recent Norwegian study, patients who visited their GP and reported sleeping fewer than six hours each night had athan those who slept seven to eight hours. Patients who suffered from chronic sleep problems were more likely to report needing antibiotics. People who slept more than nine hours each night also had a higher risk of infection, the study found. "A likely explanation for these findings could be that having an infection leads to disturbed sleep or increased sleepiness, or that both sleep and infection risk is associated with having an underlying disease," says lead author Ingeborg Forthun, a researcher at the University of Bergen in Norway. "Considering that infections are more common in the winter, it can be important to sleep more to help ward off infection," says Forthun. 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