Light pollution from outdoor lighting such as street lamps may be interfering with sleep patterns of individuals across large urban areas, according to a Canadian study.

"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," said study author Dr. Maurice Ohayon from Stanford University. "The concern is that we have reduced our exposure to darkness and it could be affecting our sleep."

The study included 15,863 people who were interviewed by phone over an eight-year period to evaluate sleep habits, quality of sleep, as well as medical and psychiatric disorders. The resulting data was validated against night-time figures from the Defense Meteorological Satellite Program.

Individuals living in urban areas of 500,000 people or more were exposed to night-time lights that were three to six times more intense than people living in small towns and rural areas. Night-time light had an impact on sleep duration and was significantly associated with sleep disturbances.

High-intensity light increased the odds of sleeping less than 6 hours per night by 6 percent, with an average of 412 minutes per night for those who were exposed compared with 402 minutes per night for those who were exposed to low-intensity light.

People with intense light exposure were more likely to be dissatisfied with their sleep quantity or quality (29 versus 16 percent), experience fatigue (9 versus 7 percent) and wake up confused during the night (19 versus 13 percent) compared with those with low-intensity light exposure. Subjects with reduced sleep duration in reported excessive sleepiness and impaired functioning.

"Light pollution can be found in any sizable city in the world. Yet, excessive exposure to light at night may affect how we function during the day and increase the risks of excessive sleepiness," said Ohayon. "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.” MIMS