By Sree Roy

I live and work in Los Angeles, and as pandemic-related restrictions continue to lift, the number of vehicles on the road has rebounded with a seeming vengeance. Dangerous driving behaviors have increased correspondingly, and I’ve seen and heard about many nearby vehicle accident near-misses and crashes. So when a press release about driving behavior and sleep apnea severity crossed my desk, I was primed to take a close look.

What impresses me about this study, done by researchers at Washington University School of Medicine in St. Louis, is it analyzes real-world behavior. Many studies of drowsy driving behaviors use driving simulators—a safe and practical way to collect data, no doubt, but a method that does not necessarily reflect what drivers do in their day-to-day lives when they have likely forgotten that their behavior is being tracked.

In this case, co-senior authors Brendan Lucey, MD (of Washington University’s Sleep Medicine Center) and Ganesh M. Babulal, PhD, OTD (a driving researcher) installed chips into participants’ personal vehicles to monitor their driving for a year. They collected a tremendous amount of data: more than 100,000 total trips.

The 96 participants were all older adults recruited from studies at Washington University’s Charles F. and Joanne Knight Alzheimer Disease Research Center (Knight ADRC). So participants were also evaluated by researchers at the Knight ADRC for cognitive impairments and molecular signs of early Alzheimer’s disease.

For sleep apnea identification, the researchers used home sleep testing, which is also how they determined each person’s apnea-hypopnea index (AHI).

The results of this observational study are compelling. For every eight additional breathing interruptions per hour, the odds of making a dangerous driving move such as speeding, braking hard, or accelerating suddenly increase by 27%, according to the study’s findings.

“We didn’t have cameras in the vehicles, so we don’t know exactly what happened that caused someone to, say, brake hard suddenly,” Babulal says in a release. “But it could be something like a stoplight that they didn’t realize was red until they got close and had to stomp on the brakes. The more tired you are, the less attention you have to deploy to the task at hand, especially if it is novel and constantly changing.”

Even though all participants were cognitively normal, about a third had brain changes indicative of early Alzheimer’s disease. The researchers found that the frequency with which drivers made dangerous driving moves rose in parallel with the frequency with which their sleep was interrupted at night, regardless of whether their brains had signs of early Alzheimer’s.

The findings make me wonder whether sleep apnea could be a modifiable risk factor for any of the driving behaviors I see around my city. What’s more, as the authors note, maybe treating sleep apnea would prolong safe driving in old age.

Lucey says, “These findings suggest that we might want a lower threshold to evaluate older adults for sleep apnea and track their breathing interruptions. If their conditions worsen by just eight interruptions an hour, that could have significant adverse effects on their driving and their risk of suffering serious injury.”

Sree Roy is editor of Sleep Review.

Photo 100501835 / Car Brake Pedal © Asawin Kanakasai |