Michigan State Police Sgt. Chris Pascoe of the Ypsilanti post says getting four hours of sleep for five consecutive nights is like staying awake for 24 hours. And that's like drunken driving.

About one-fifth of vehicle crashes and near crashes nationally are caused by drowsy drivers, and about one-third of fatal truck crashes are, Pascoe said.

That's why this week is Drowsy Driving Awareness Week, designed to bring attention to problem — which may not be as recognizable of an issue as drunken driving or texting while driving, officials say.

The National Highway Transportation Safety Administration estimates 100,000 crashes reported to police each year are caused by driver fatigue, resulting in 1,500 deaths and 71,000 injuries.

Drowsy driving may cause slowed reaction time, decreased awareness, impaired judgment and increased risk of crashing, according to the Michigan State Police website.

Police say adults need seven to nine hours of sleep each night, and tired drivers should take breaks every 100 miles or every two hours while driving long distances.

The AAA Foundation for Traffic Safety conducted a study that found younger drivers — ages 16-24 — were nearly twice as likely to be involved in a drowsy driving crash than drivers ages 40-59. About 57 percent of drowsy driving crashes involved the driver drifting into other lanes or even off the road.

Drivers should avoid getting behind the wheel if they're too tired.

According to the foundation’s 2009 Sleep in America poll, about 28 percent of Americans admitted they've fallen asleep behind the wheel within the past year, and 54 percent said they have driven while drowsy.

One culprit for drowsy driving could be undiagnosed obstructive sleep apnea, according to the Detroit Dental Sleep Network, which aims to educate the community about the problem during Drowsy Driving Awareness Week.

An estimated 18 million Americans are affected by OSA — which causes constant sleep deprivation — and only about 10 percent of sufferers are diagnosed, the Dental Sleep Network said in news release.

That constant state of sleep deprivation is linked to drowsy driving, said Alan Barnes, facilitator of the Detroit Dental Sleep Network.

Barnes said some signs of OSA include dozing off or falling asleep during daily activities, while at work, waiting at a red light or while talking with others. Barnes said being overweight can increase one's risk of developing OSA.

Think you may have OSA? Download the Epworth Sleepiness Scale, or call 1-877-337-7689 for a free, 90-second sleep screening.

The AAA Foundation for Traffic Safety also has a brochure on how to avoid drowsy driving that debunks some myths — such as the the answer is just to consume more caffeine.

Heather Lockwood is a reporter for AnnArbor.com. Reach her at heatherlockwood@annarbor.com or follow her on Twitter.