The National Highway Traffic Safety Administration has estimated that 1 percent to 4 percent of highway crashes and 4 percent of fatal crashes are caused by sleepiness. Many sleep researchers think those numbers are too low.

"Sleepiness can kill you quick," said one expert. A driver who nods off at 60 mph can drift off the highway at a four-degree angle in less than four seconds, he said.

Drowsy driving represents perhaps the greatest risk to those who have inadequate sleep. Crashes linked to drowsy driving peak between 3 a.m. and 8 a.m.

While there is increasing research evidence on the harmful effects of disturbed sleep, getting the word out beyond the lab has lagged, specialists said.

Surgeon General Richard Carmona told the conference: "Improving health literacy on sleep disorders is long overdue." Several participants called for a surgeon general's report on sleep and public health, comparable to the landmark report on smoking and health in 1964 that started to tip the balance of public opinion on tobacco use.

According to the conference organizers, 50 million to 70 million Americans suffer health consequences of sleep disorders, sleep deprivation and excessive daytime sleepiness each year, adding about $15 billion to the nation's healthcare bill and costing industry about $50 billion in lost productivity.

The groups at risk for sleep-related vehicle crashes include those who sleep fewer than six hours a day; young adult males ages 16 to 24; commercial drivers; night-shift workers; those driving after prolonged work hours, such as medical residents at hospitals, and patients with untreated sleep disorders.

Dr. Daniel Buysse, a University of Pittsburgh psychiatrist, said it is time for physicians to stop regarding insomnia as "a nuisance symptom." It is a disorder with real consequences, he said, including increased absenteeism at work, higher risk of being involved in a motor vehicle accident and increased risk of cognitive decline in later years.