There is a growing perception that fatigue or sleepiness in car drivers increases their risk of crash. This hypothesis has biological plausibility, is supported by descriptive information about road crashes, and has important policy implications. To assess the available evidence for a causal role of fatigue in car crashes, and to quantify the effect, a systematic review of the international literature has been conducted. The review was restricted to studies with a fatigue-related exposure measure, a crash or crash injury outcome measure and a comparison group. Sixteen cross-sectional studies fulfilled the inclusion criteria. No cohort or case control studies, or studies with injury outcomes, were found. Studies were limited in their ability to establish a causal relationship by design, biases, and in many cases, small sample sizes. The better quality studies were suggestive of a positive relationship between fatigue and crash risk, but no reliable estimates of the strength of the association are available. We conclude that the direct evidence for a causal role of fatigue in car crashes is weak. To estimate the burden of fatigue-related crashes in the population, information is required from well-designed observational epidemiological studies about the prevalence of fatigue in the car driving population and the size of the risk this confers. (A)
Abstract