Can't sleep? Blame your road's street lamps! Light pollution outside bedrooms is linked to sleepless nights

Having trouble sleeping? You may want to invest in some thicker curtains.

A large study has found that street lights may be interfering with the sleep of millions of people in urban areas around the world.

The research found those living in towns and cities of more than 500,000 people were exposed to light levels far higher than those in smaller towns and rural areas, had less sleep and suffered more fatigue.

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Can't sleep? A study of almost 16,000 people found light pollution affects sleep levels. Researchers from Stanford University found night-time lighting affected quality and quantity of sleep. Stock image

Researchers at Stanford University in California interviewed 15,863 people over the phone during an eight-year period, quizzing them about their sleep habits, the quality of sleep and whether they had any medical or psychiatric disorders.

They then combined the questionnaire results with satellite data to show how much light the people were exposed to in the different areas as they slept.

The Stanford team found that people living in more urban areas were exposed to levels of light between three to six times brighter than those based in small towns and rural areas.

People in more urban areas, with more than half a million people, were exposed to levels of light between three to six times brighter than those based in small towns and rural areas. Stock image

In addition, people exposed to more intense levels of light at night-time were also more likely to wake up confused in the night as well as being fatigued the next day. Stock image

People living in more intense light areas were six per cent more likely to sleep less than six hours per night than people in less intense light areas.

In addition, those living in the brighter areas were also more likely to be dissatisfied with their sleep quantity or quality than people in less intense light areas - 29 per cent and 16 per cent respectively.

They were also more likely to wake up confused in the night as well as being fatigued the next day, compared to their counterparts who evaded the bright lights at night.

Dr Maurice Ohayon, a researcher in sleep, psychology and neurology at Stanford and author of the study, said: 'Our world has become a 24/7 society. We use outdoor lighting, such a street lights, to be more active at night and to increase our safety and security.

He added: 'The concern is that we have reduced our exposure to darkness and it could be affecting our sleep.'

By combining the data from the questionnaires with that from the Defence Meteorological Satellite Programme, the researchers were able to link light pollution with negative impacts on sleep on such a large scale.

While the initial results do not explicitly mention factors such as noise or the effect of traffic or pets, they could be expanded to cities around the world.

The group's findings are due to be presented at the annual meeting of the American Academy of Neurology, which will take place in Vancouver in April. 

Dr Ohayon added: 'Light pollution can be found in any sizeable city in the world.

People in more urban areas were exposed to levels of light up to six times brighter than those based in small towns and rural areas, say researchers 

'Yet, excessive exposure to light at night may affect how we function during the day and increase the risks of excessive sleepiness.

'If this association is confirmed by other studies, people may want to consider room darkening shades, sleep masks or other options to reduce their exposure.'

Prolonged lack of sleep, over a number of years, can increase a person's risk of a number of health conditions, from diabetes to dementia and even stroke.

Researchers believe that the chronic sleep deprivation stops the brain's restorative mechanisms from carrying out repairs and clearing out waste products. 

Without these crucial processes the brain can effectively fall into disrepair, with altered brain chemistry and ultimately, altered brain structure.