Shift work sleep disorder (SWSD) increases the likelihood of having a collision by a staggering 300% as compared to insomnia and sleep apnea which both up the odds by about 30%, according to new research from the University of Missouri.

A chronic medical condition, many people who work non-traditional hours like 11 pm to 7 am suffer from shift SWSD. The latest findings indicate that these people — including fleet drivers who work the graveyard shift — are exceptionally vulnerable to drowsy driving.

Drowsy-driving crashes are particularly high for shift workers due to disruption of their natural sleep pattern, according to the study. While driving, lack of sleep results in slower reaction time, poor coordination, and less ability to pay attention.

What’s more, older drivers with SWSD are at an even greater risk. The study showed that those over age 65 with SWSD are 5.89 times more likely to be involved in a crash or near-crash. In comparison, drivers between ages of 25 and 44 with SWSD were 2.42 times more likely to be involved in a crash or near-crash.

The study also found that individuals with any sleep disorder are 29% more likely to be inattentive while behind the wheel as compared to drivers without a sleep disorder. 

The authors say the study results point to a real need for counter measures aimed at preventing these crashes. For example, solutions might include the availability of more highway rest areas as well as roadside and in-vehicle messaging to improve a driver’s attention and focus.

The methodology of this study sets it apart because the research team evaluated real-world data. Most previous studies on drowsy driving were conducted in a controlled environment, like a laboratory driving simulator.

Conversely, this latest analysis was based on actual observed crash and near-crash data from an estimated 2,000 events across six states.

The authors say the real-world crash data validates the efforts of previous studies while also accounting for confounding variables such as roadway and traffic characteristics.

Nearly 700 people lost their lives in drowsy driving crashes in 2019 alone, according to the National Traffic Highway Safety Administration.