Sleepy drivers 'dangerous as drunks'

Staying alert was more difficult for those with disrupted sleep

A lack of sleep can reduce mental functioning as significantly as drinking too much, a study has found.

The findings suggest that driving when tired is as dangerous as driving drunk.

The research looked at people with mild to moderate sleep apnoea, a condition that interrupts a person's sleep without them realising it.

The researchers at Stanford University, in California, that people with the disorder performed as badly on tests of reaction times as people who had drunk too much to be able to drive a bus or lorry under Californian law.

In three out of the seven tests, people with sleep apnoea did as poorly as those not allowed to drive at all in states where - as in California - 0.08% alcohol in the blood stream is the limit.

Extreme snoring

Sleep apnoea occurs when the throat temporarily closes during sleep. The sleeper wakes violently because of a lack of oxygen.

The condition, which is more common in overweight people, can cause extreme fatigue because many hours of sleep are lost.

The condition can be detected by monitoring sleeping patterns

It can be identified only through monitoring the way people sleep.

Dr Nelson Powell's study looked at 113 people with the condition along with 80 volunteers.

Their reaction speed was tested, and, once an average time had been set, the volunteers started drinking.

They were re-tested three times - once with a blood alcohol content level of 0.05%, once at 0.8% and then again at 0.83%.

Legal limits

Californian law says it is illegal for anyone with a blood alcohol level greater than 0.04% to drive a bus or a truck, and in 16 states 0.08% is the legal definition of drunk.

Volunteers were judged in comparison to legal limits of alcohol

The people with apnoea were monitored as they slept, and on average their breath 29 times an hour when they were asleep.

They performed worse than the volunteers on all counts at the first re-test, and on three measurements at when the volunteers were legally drunk.

Dr Powell presented his study at the American Academy of Otolaryngology-Head and Neck Surgery Foundation's annual convention in New Orleans.

"How many times have you or anybody you've known been nodding off at the wheel, or said, 'Gee, I've got to roll the window down or turn the music louder'?" he said.

"I'd bet every driver, at one time or another has driven too tired. We know it's wrong but we still do it."

Change of perspective

Dr Regina Walker, an ear nose and throat specialist at Chicago's Loyola University, said: "This is a wonderful study.

"It is an extremely well thought out, well-controlled, prospective study that is looking at something I think is of great significance.

"Many of my patients don't think being sleepy is a big deal. I think this will help legislators and the public understand just how serious the problem is."