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Several chronic medical conditions and sleep disorders can potentially compromise sleep and elevate feelings of fatigue (Smolensky et al., 2011). Three disorders, in particular, can cause drivers to fall asleep at the wheel. Insomnia is the subjective experience of having difficulty falling asleep or staying asleep. It affects an estimated 11% of the U.S. population (NSF, 2008). People suffering from insomnia often report daytime sleepiness that interferes with their daily activities. Several studies suggest that people suffering from insomnia are two to three times more likely to be involved in motor vehicle crashes compared to those without insomnia (Smolensky et al., 2011).

Obstructive sleep apnea is a breathing disorder characterized by brief interruptions of breathing during sleep (Punjabi, 2008). By fragmenting nighttime sleep, sleep apnea produces daytime sleepiness. NSF estimates that about 4% of men and 2% of women are affected by sleep apnea. It can be treated by physical or mechanical therapy or by surgery. Research shows that people with sleep apnea are up to six times more likely to be involved in a crash (Teran-Santos et al., 1999). It has been estimated that crashes among people with obstructive sleep apnea cost approximately $16 billion each year (Sassani et al., 2004).

Narcolepsy is a disorder of the central nervous system’s sleep-wake mechanism that can cause narcoleptics to fall asleep suddenly at any time (Suni & DeBanto, 2021). It is quite rare, affecting about one person in 2,000 and can be treated with medications. The number of crashes resulting from narcolepsy is not known.

Most cases of obstructive sleep apnea or narcolepsy are undiagnosed and untreated (Stutts et al., 2005; NHTSA, 1998). Indeed, falling asleep at the wheel may be one of the main ways to raise the possibility of a sleep disorder and motivate a driver to seek medical attention (NHTSA, 1998). Once treated, people with obstructive sleep apnea have crash rates that are no higher than the general population (George, 2001).

Aside from the three sleep disorders mentioned above, there are many other medical conditions that can potentially compromise sleep or increase daytime feelings of fatigue such as asthma, chronic obstructive pulmonary disease, and rheumatoid or osteoarthritis.

Many common prescription and over-the-counter medications can also cause drowsiness. One study of the sedative Zolpidem by drivers 70 and older in Alabama found increased at-fault crash rates in women and drivers 80 or older when compared with non-users (Booth et al., 2016). Warning labels on the medications note this and caution users against driving or other activities that could be affected by drowsiness.

The principal countermeasures to address medical conditions and medication effects are (Stutts et al., 2005):

  • Communications and outreach on sleep disorders to increase overall awareness of their symptoms, consequences, and treatment.
  • Efforts with driver licensing medical advisory boards to increase their awareness of these conditions as they review driver fitness for licensing.
  • Efforts with physicians to increase their awareness of these conditions and their potential effects on driving, to treat these conditions as appropriate, and to counsel their patients to take steps to reduce the risk of drowsy driving.

Additionally, it is important that pharmacies and drug makers include patient education about the potentially impairing effects of certain medications on driving (Smith et al., 2018). Prescription labeling by drug makers, as well as incorporation of electronic prompts when dispensing medication, can be other promising opportunities for patient education (Smith et al., 2018). One survey study found that while pharmacists generally provide warnings on sedatives and narcotics to many patients (about 85% of 7,405 people surveyed), fewer people receive warnings on antidepressants (62.6%) and stimulants (57.7%) (Pollini et al., 2017).

Education campaigns can be hard to evaluate due to the difficulty in measuring behavior change. It is unclear from the limited literature that any of these efforts results in people engaging in strategies to minimize the effects of their medical condition or medicine. Raising awareness about the risks is not necessarily the same as teaching mitigation skills and then having people implement them.