Effects of Drowsiness at Work


People who get drowsy in the daytime are twice as likely as others to be involved in traffic crashes or accidents involving the use of heavy machinery, a British study reports.

Sleepiness has been implicated in about one out of six motor-vehicle crashes in England, and in about half of all injurious accidents at work and a quarter of those at home, researchers noted.

Their study, based on telephone interviews with a random sample of the British population, included nearly 5,000 people over age 15. About 6% reported severe daytime sleepiness, and another 15% reported moderate daytime sleepiness. Previous estimates of the prevalence of daytime sleepiness, depending on the definition, have ranged from less than 1% to 40%.

Severe daytime sleepiness in the British study was defined as being very sleepy on a daily basis for at least a month; moderate daytime sleepiness meant being moderately sleepy every day for at least a month.


Daytime sleepiness is more common among women, “middle-aged” (25 to 44 years old) people and those who tend to fall asleep while reading or watching television, the study found. It was also associated with napping, insomnia, heavy consumption of caffeine and depression.


Daytime consumption of alcohol did not seem to be a factor in daytime sleepiness, but severe daytime sleepiness was 60% more likely in cigarette smokers than in nonsmokers. Two diseases that often hinder sound sleep, arthritis and heart disease, were linked in the study to moderate but not severe daytime sleepiness.

The study was led by doctors from the Centre de Recherche Philippe Pinel in Montreal. Also participating were researchers from Bordeaux, France, the Sleep Disorders Center at Stanford University School of Medicine, and the University of London. Their results were published this month in the Archives of Internal Medicine.

The high rates of daytime sleepiness and the seriousness of its consequences, researchers concluded, “mandate further scrutiny by public-health officials,” including efforts to educate the public about the dangers of drowsiness.