• The use of smartphones while operating a motor vehicle has led to an increased number collisions in Washington State. However, other issues that drivers faced long before the appearance of mobile phones still remain a significant factor in the cause of many crashes: lack of sleep.

    With an estimated 25-30% of adults sleeping 6 or less hours per night, lack of sleep can lead to other health conditions such as obesity, hypertension, diabetes, and coronary disease.[1]  According to the Center for Disease Control, getting less than six hours of sleep per night can make a driver 2.6 times more likely to fall asleep while driving.[2]  Sleep apnea in particular has become a common chronic condition, with 17% of women and 34% of men estimated to be suffering from this sleep disorder, and in turn plays a big role in the danger of drivers falling asleep while driving.

    A 2018 cohort study evaluated 1,745 men and 1,456 women in an attempt to determine not only how lack of adequate sleep affects driving, but specifically whether there was an increased risk of motor vehicle collisions among drivers with sleep apnea.[3] Participants began by undergoing a night of polysomnography (a sleep study) and completing a questionnaire of their sleeping patterns. A second questionnaire was completed two years later, in which the participants were asked to describe their driving history more fully. Based on the results of their sleep study, participants were separated into one of three categories: those that suffered from mild, moderate, or severe sleep apnea.

    Compared to drivers without sleep apnea, participants with mild sleep apnea were 7% more likely to be involved in a motor vehicle crash. Those suffering from moderate sleep apnea were 13% more likely to be involved in such a crash. The study concluded that a key factor in these first two populations was whether the participant received at least six hours of sleep.

    Strikingly, participants suffering from severe sleep apnea were 123% more likely to be involved in a crash, regardless of how many hours of sleep they received.[4] The study found that for every hour of sleep lost, the odds of participants being involved in a crash increased by 13%. There were no significant differences on the effects of sleep apnea and sleep duration between men and women, among different body mass indexes, or between younger and older participants. Only 2.2% of the participants reported receiving treatment for their sleep apnea, which did not change the results of the study. The statistical results of the study were also not affected by participants who did not subjectively feel more sleep deprived, including those with severe sleep apnea.  This led the researchers to comment that excessive sleepiness should not be a controlling factor in whether someone is diagnosed with or treated for sleep apnea.

    In short, untreated sleep deficiency caused by sleep apnea was found to be associated with a substantial increase in motor vehicle crashes, regardless of whether the driver felt sleepy. This study highlights the importance of addressing lack of sleep as a continuing cause of motor vehicle collisions.

    In a legal case to recover damages due to the negligence of a sleep-deprived driver, having access to that driver’s prior medical history may help shed light on the actual causes of a crash. Since disrupted sleep is also a common result of patients dealing with traumatic injury, the study also underscores the need for those suffering from trauma to pay close attention to their sleep cycles as they go about recovering from their injuries, taking medications, working long shifts, or re-engaging in driving.


    [1] Colten HR, Altevogt BM, editors. Sleep disorders and sleep deprivation: an unmet public health problem. Washington, D.C.: The National Academies Press; 2006.

    [2] Centers for Disease Control and Prevention. Drowsy Driving – 19 States and the District of Columbia. MMWR. 2013;61:1033–7.

    [3] Gottlieb, Ellenbogen, Bianchi, and Czeisler. Sleep deficiency and motor vehicle crash risk in the general population: a prospective cohort study. BMC Medicine, 20 March 2018 16:44.

    [4] Severe sleep apnea was defined as 30 or more apneas (complete loss of breath) or hypopneas (partial loss of breath) per hour.


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