Insomnia may be a major contributor to road-related deaths and other unintentional fatal injuries, a new study suggests.

Insomnia is a sleep disorder which results in people constantly having difficulties falling asleep or staying asleep. This can lead to a number of problems such as daytime fatigue, irritability, depression, poor concentration and poor coordination.

The Norwegian study involved almost 55,000 men and women aged between 20 and 89. Deaths as a result of unintentional fatal injuries, including road accidents, were kept track of over a 13-year period.

The study found that a person's risk of suffering an unintentional fatal injury increased the more symptoms of insomnia they had. People with three symptoms were 2.8 times more likely to die as a result of a fatal injury compared to people with no symptoms of the sleep disorder.

These results stood even when other risk factors were taken into account, such as the use of sleep medication and alcohol use.

Among the symptoms of insomnia, having trouble falling asleep appeared to have the strongest link with fatal injuries. Those who always had problems falling asleep were at least two times more likely to die in a road accident, and at least 1.5 times more likely to die from any unintentional fatal injury, compared to those who never had problems falling asleep.

A further analysis by the researchers suggested that problems falling asleep contributed to 34% of road-related deaths and 8% of all unintentional fatal injuries. These could have been avoided if insomnia was not present, they said.

"Our results suggest that a large proportion of unintentional fatal injuries and fatal motor vehicle injuries could have been prevented in the absence of insomnia.

"Increasing public health awareness about insomnia and identifying and treating people with insomnia may be important in preventing unintentional fatal injuries," commented the study's lead author, Dr Lars Laugsand, of the Norwegian University of Science in Technology.

Details of these findings are published in the journal, Sleep.