Effect of a community-based sleep extension intervention on young adults’ sleep and risky driving propensity: a randomised controlled trial

Background Insufficient sleep is a key risk factor for road vehicle crashes in young adults. This trial evaluated the effectiveness of a sleep extension intervention on reducing on-road risky driving in young adult drivers who self-identified as sleepy. Methods Australian drivers (18–24 years old), reporting insufficient sleep (average <7 h/night and <6 h at least twice weekly) were randomized to either a sleep extension intervention, or nutrition information placebo. The intervention included a personalized sleep extension schedule and sleep education; the control group received nutrition information only. Outcomes were assessed using wrist and in-vehicle accelerometers during three two-week assessment periods (baseline, post-intervention, and 6-month follow-up), followed by laboratory assessments. Primary outcomes were changes in objective and subjective sleep (sleep duration, short sleep episodes, and quality), and driving behaviour (proportion of harsh starts/stops and turns exceeding acceleration thresholds). Analyses followed an intention-to-treat approach. Results Ninety-nine drivers completed the study ( Mage = 20.62, SD = 1.90, 73% female). The intervention group showed significant reductions in harsh starts/stops (β = −0.14, p = 0.024) and harsh turns (β = −0.07, p = 0.036) post-intervention compared to controls, though effects were not sustained at follow-up. No significant between-group differences were observed for objective sleep duration or short sleep frequency. Subjective sleep-related daytime impairment decreased post-intervention in the intervention group (β = −5.64, p = 0.002), but not at follow-up. Conclusion Sleep extension and education-focussed interventions may be effective at reducing crash risk in young adults. Further research is needed to support long-term maintenance and integration into road safety strategies.