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Sleep Deprivation: The Risks of Surviving on Two Hours of Sleep

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Understanding the Dangers of Drowsy Driving

In this article, we explore the alarming consequences of drowsy driving, shedding light on its life-changing impact. We emphasize the critical need for awareness and caution, as well as the potential legal implications associated with impaired driving due to sleep deficiency.

A Tragic Incident

On a fateful morning in August 2008, Candy Lynn Baldwin, a nineteen-year-old driver, experienced a life-altering event. After staying awake for an extended period, she tragically fell asleep behind the wheel while crossing the Chesapeake Bay Bridge. The consequences were devastating as her vehicle swerved and collided with a semi-truck, subsequently plunging into the bay. Although Baldwin survived with non-life-threatening injuries, the truck driver lost their life. This heartbreaking incident serves as a poignant reminder of the dangers posed by drowsy driving.

The Grim Reality

Unbeknownst to many, drowsy driving claims the lives of more than 6,000 individuals each year. Shockingly, this figure includes fatal accidents involving renowned figures like comedian Tracy Morgan and Maggie McDonnell. Morgan's limousine was struck by a truck whose driver had been without sleep for a staggering 24 hours. Similarly, McDonnell lost her life in a head-on collision caused by a truck driver who had been awake for an uninterrupted 30 hours. Tragically, Maggie McDonnell's death inspired the implementation of "Maggie's Law" in New Jersey, which prohibits driving while knowingly impaired by sleep deprivation.

Determining the Threshold

Uncovering the precise degree of sleepiness that renders driving unsafe is a complex matter. To address this, the National Sleep Foundation assembled a panel of sleep medicine and transportation industry experts. Their task was to ascertain the factors influencing sleepiness levels beyond sleep duration alone. The panel identified that pre-existing sleep debt significantly intensifies the impact of acute sleep deficiency. Moreover, the time of day plays a crucial role, with the body's circadian rhythm predisposing individuals to decreased alertness during nighttime hours. It is important to consider these factors along with the quality of sleep obtained, as attempting to compensate for sleep debt in a noisy motel room next to railroad tracks proves counterproductive.

After careful evaluation of these variables, the panel concluded that driving with less than two hours of sleep in the preceding 24 hours signifies impairment.

A Call for Perspective

Despite the two-hour threshold, it is vital to understand that sleeping for this minimum duration does not guarantee safety while operating a vehicle. The impact of sleep deficiency remains significant even if individuals sleep for double this recommended amount. Dr. Charles Czeisler, chair of the panel and a prominent sleep medicine expert, stresses that this threshold acts as a warning and should guide public policy, much like the legal definition of driving under the influence at a blood alcohol content greater than .08%.

Mitigating Sleep Deficiency's Effects

While stimulants like caffeine offer temporary relief from sleepiness, they are not a long-term solution. Methods such as increasing the volume of the radio or opening the car window have been debunked as ineffective coping mechanisms. It is important to note that feeling awake does not necessarily correlate with optimum driving performance. Only sufficient sleep can truly reverse the impacts of sleep deficiency.

An Alarming Public Health Hazard

Drowsy driving poses a significant public health risk in the United States, accounting for an estimated 20% of all motor vehicle crashes. This equates to over 1 million crashes annually, a number that may be significantly higher due to underreporting. To address this issue, it is essential for individuals to refrain from driving without adequate sleep. While the two-hour threshold marks the lower limit, it is crucial not to underestimate the risks even if one has slept longer. Remember, the wise course of action is simple: "Sleep-Deprived? Don't Drive."


Awareness and education are paramount in combating the dangers of drowsy driving. By understanding the critical nature of sleep and its undeniable impact on driving abilities, we can work towards a safer future on our roads. Let us prioritize our well-being and that of others by ensuring we are well-rested before getting behind the wheel.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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