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Review
. 2023 Apr 4:15:175-206.
doi: 10.2147/NSS.S392441. eCollection 2023.

How Tired is Too Tired to Drive? A Systematic Review Assessing the Use of Prior Sleep Duration to Detect Driving Impairment

Madeline Sprajcer  1 , Drew Dawson  1 , Anastasi Kosmadopoulos  1 , Edward J Sach  1 , Meagan E Crowther  1 , Charli Sargent  1 , Gregory D Roach  1
Affiliations
Review

How Tired is Too Tired to Drive? A Systematic Review Assessing the Use of Prior Sleep Duration to Detect Driving Impairment

Madeline Sprajcer et al. Nat Sci Sleep. .

Abstract

Driver fatigue is a contributory factor in approximately 20% of vehicle crashes. While other causal factors (eg, drink-driving) have decreased in recent decades due to increased public education strategies and punitive measures, similar decreases have not been seen in fatigue-related crashes. Fatigued driving could be managed in a similar way to drink-driving, with an established point (ie, amount of prior sleep) after which drivers are "deemed impaired". This systematic review aimed to provide an evidence-base for the concept of deemed impairment and to identify how much prior sleep may be required to drive safely. Four online databases were searched (PubMed, Web of Science, Scopus, Embase). Eligibility requirements included a) measurement of prior sleep duration and b) driving performance indicators (eg, lane deviation) and/or outcomes (eg, crash likelihood). After screening 1940 unique records, a total of 61 studies were included. Included studies were categorised as having experimental/quasi-experimental (n = 21), naturalistic (n = 3), longitudinal (n = 1), case-control (n = 11), or cross-sectional (n = 25) designs. Findings suggest that after either 6 or 7 hours of prior sleep, a modest level of impairment is generally seen compared with after ≥ 8 hours of prior sleep (ie, well rested), depending on the test used. Crash likelihood appears to be ~30% greater after 6 or 7 hours of prior sleep, as compared to individuals who are well rested. After one night of either 4 or 5 hours of sleep, there are large decrements to driving performance and approximately double the likelihood of a crash when compared with well-rested individuals. When considering the scientific evidence, it appears that there is a notable decrease in driving performance (and associated increase in crash likelihood) when less than 5h prior sleep is obtained. This is a critical first step in establishing community standards regarding the amount of sleep required to drive safely.

Keywords: driving; fatigue; performance; safety; sleep.

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Conflict of interest statement

Professor Gregory Roach reports grants from Department of Infrastructure, Transport, Regional Development Communications and the Arts, during the conduct of the study. The authors declare no other conflicts of interest in this work.

Figures

Figure 1
Figure 1
PRISMA flowchart.
Figure 2
Figure 2
Odds ratios for case–control studies assessing the likelihood of a crash based on prior sleep. †OR of a fatigue crash vs non-fatigue crash, *OR of a fatigue crash vs no crash. Note Ref categories differ between studies (range: 6–8 h) but reflect a greater amount of prior sleep.
Figure 3
Figure 3
Odds ratios for cross-sectional studies assessing the adverse driving outcomes based on prior sleep. Note Ref categories differ between studies (range: 6–8 h) but reflect a greater amount of prior sleep.
Figure 4
Figure 4
Odds ratios for cross-sectional and case–control studies assessing the likelihood of an adverse driving outcome (driving errors, falling asleep while driving, or crashing) based on prior sleep. Note Ref categories differ between studies (range: 6–8 h) but reflect a greater amount of prior sleep. †Fatigued crash versus non-fatigued crash. *Fatigued crash versus no crash.
Figure 5
Figure 5
Forest plot of odds ratio meta-analysis for five hours sleep vs less than five hours sleep. Diamond presents the pooled odds ratio of studies included in meta-analysis. Dotted line denotes the odds ratio prediction interval.
Figure 6
Figure 6
Forest plot of odds ratio meta-analysis for six hours or more sleep vs less than six hours sleep. Diamond presents the pooled odds ratio of studies included in meta-analysis. Dotted line denotes the odds ratio prediction interval. The red rectangle denotes the predicted confidence interval for pooled effect.
Figure 7
Figure 7
Forest plot for meta-analysis of seven hours or more sleep vs less than seven hours sleep. Diamond presents the pooled odds ratio of studies included in meta-analysis. Dotted line denotes the odds ratio prediction interval. The red rectangle denotes the predicted confidence interval for pooled effect.
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Grants and funding

This systematic review is supported by the Australian Government Office of Road Safety’s Road Safety Innovation Fund (RSIF2-73).

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