P108 Association of drowsiness events with a combination of sleep loss and other work metrics

Abstract

Abstract Introduction Heavy vehicle drivers (HVDs), carrying approximately 75% of non-bulk domestic freight on Australian roads, are at risk of drowsiness due to night-time, long drives, or short sleep. Drowsiness comprises 46% of all driver-impairment-related factors in HVDs fatalities. However, the specific role of sleep loss in HVDs' drowsiness is less known. This study assessed the association of sleep loss, independent of other work metrics, with real-time drowsiness in HVDs. Methods Eight HVDs aged 49.8± 8 years, 27± 10.3 years of experience, worked for 3-28 (13± 6) shifts. A composite ocular measure of drowsiness (John's Drowsiness Score) and drivers' sleep-wake was monitored by Optalert glasses and Actiwatches, respectively. The drowsiness event (response variable) was defined as at least one event of JDS≥ 2.6 /h, and sleep loss (exposure) as the variation of sleep opportunity pre-shift from the 9-hour recommended rest break in Europe. Multivariate logistic regression assessed the odds of drowsiness events under sleep loss when adjusted for time of day, shift start time and hours of drive. Results Data comprised 1061 observations of work metrics or JDS and 694 records of sleep duration. Sleep loss ranged from 1 to 6.3 hours (3.4 ± 1.1h). Compared with a 1- 2.5-hour sleep loss, sleep loss> 4 hours doubled the likelihood of drowsiness events when controlled for other covariates (p=0.019). Discussion Sleep loss increases the odds of drowsiness events in HVDs with similar work schedule metrics. Further research should assess if Australia's 7-h minimum break provides adequate sleep under different schedule conditions.