Nightshift workers should consider wearing sunglasses to try to reduce the risks to their health from light, according to a sleep expert. Their exposure to light during night work has been shown to lower melatonin levels and significantly disrupt sleep patterns. Previous studies have shown that disruptions to sleep and melatonin levels can cause an increase in workplace accidents but can also lead to health problems. This has led the World Health Organisation to put shift work on its list of potential carcinogens because of the impact upon circadian rhythms – the 24-hour internal clock that cycles between sleepiness and alertness at regular intervals. Sleep disorder expert Dr Guy Leschziner, a consultant neurologist at Guy’s and St Thomas’ Hospitals in London, said: “We know that however disrupted circadian rhythms are, it is not good for your health. “There are theories that melatonin may be protective against cancer. “The key thing is to ensure you are not damaging your internal circadian rhythm by not exposing yourself to bright light; for example, when you are going home. “For people that have grave difficulties dealing with their shift patterns, even wearing sunglasses on the way home to try and allow the melatonin levels to come up as much as possible.” Dr Leschziner, who was speaking at an event at the Cheltenham Science Festival on sleeping, said genetics plays an important role in how much sleep people need and how affected they are by shift work, by drinking caffeine late at night, or watching television or using computers in bed. “If your sleep is of really good quality and you sit there watching Netflix until 11pm at night, close the computer and drift off to sleep and have a great night’s sleep, then you don’t need to worry about it,” he said. “We know there are genes that influences how your brain processes caffeine. There will be people out there who will drink two or three cups of espresso before bed and it will have no impact at all. “We do have very clear evidence that exposure to blue light for relatively short periods of time in the evening have really quite significant consequences upon melatonin. “Melatonin is a very potent regulator of your drive to sleep and regulator of your circadian rhythm. We know that the sensitivity to blue light varies tremendously. “There will be some individuals who are exposed to blue light in the evening and have relatively few consequences on the circadian rhythm and melatonin. “But in other individuals it has massive consequences. Everybody is different and these hard and fast rules are not applicable to everyone in the population. “It is only an issue if it disrupts your sleep.” Dr Leschziner also said that daytime naps had recently been shown to improve blood pressure but could disrupt night-time sleeping consequently. “What we know, as you get older there is a view you need less sleep, but this is not borne out by the evidence,” he said. “It seems older people need the same as when they are middle-aged, it just that the brain is less good at consolidating sleep and remaining in deep sleep. “Sleeping becomes more fragmented and the drive to remain asleep is a little bit weaker. The quality of sleep may deteriorate in some individuals. “I think whether you need a nap is related to how much sleep you are getting at night and whether a daytime nap gets in the way of anything else you want to do.”