Young drivers (18-24 years) are over-represented in sleep-related crashes (comprising one in five fatal crashes in developed countries) primarily due to decreased sleep opportunity, lower tolerance ...for sleep loss, and ongoing maturation of brain areas associated with driving-related decision making. Impaired driving performance is the proximal reason for most car crashes. There is still a limited body of evidence examining the effects of sleep loss on young drivers' performance, with discrepancies in the methodologies used, and in the definition of outcomes. This study aimed to identify the direction and magnitude of the effects of sleep loss on young drivers' performance, and to appraise the quality of current evidence via a systematic review. Based on the Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) approach, 16 eligible studies were selected for review, and their findings summarised. Next, critical elements of these studies were identified, and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines augmented to rate those elements. Using those criteria, the quality of individual papers was calculated and the overall body of evidence for each driving outcome were assigned a quality ranking (from 'very low' to 'high-quality'). Two metrics, the standard deviation of lateral position and number of line crossings, were commonly reported outcomes (although in an overall 'low-quality' body of evidence), with significant impairments after sleep loss identified in 50% of studies. While speed-related outcomes and crash events (also with very low- quality evidence) both increased under chronic sleep loss, discrepant findings were reported under conditions of acute total sleep deprivation. It is crucial to obtain more reliable data about the effects of sleep loss on young drivers' performance by using higher quality experimental designs, adopting common protocols, and the use of consistent metrics and reporting of findings based on GRADE criteria and the PRISMA statement. Key words: Young drivers, sleep loss, driving performance, PRISMA, the GRADE, systematic review.
Most objective drowsiness measures have limited ability to provide continuous, accurate assessment of drowsiness state in operational settings. Spontaneous eye blink parameters are ideal for ...drowsiness assessment as they are objective, non-invasive, and can be recorded continuously during regular activities. Studies that have assessed the spontaneous eye blink as a drowsiness measure are diverse, varying greatly in respect to study design, eye blink acquisition technology and eye blink parameters assessed. The purpose of this narrative review is to collate these studies to determine 1) which eye blink parameters provide the best state drowsiness measures; 2) how well eye blink parameters relate to and predict conventional drowsiness measures and 3) whether eye blink parameters can identify drowsiness impairment in obstructive sleep apnoea (OSA) - a highly prevalent disorder associated with excessive sleepiness and increased accident risk. In summary, almost all eye blink parameters varied consistently with drowsiness state, with blink duration and percentage of eye closure the most robust. All eye blink parameters were associated with and predicted conventional drowsiness measures, with generally fair to good accuracy. Eye blink parameters also showed utility for identifying OSA patients and treatment response, suggesting these parameters may identify drowsiness impairment in this group.
Young drivers are over-involved in sleepiness-related crashes. The alerting effects of bright light offer a potential countermeasure for driver sleepiness, either replacing or in conjunction with ...current countermeasures such as the use of caffeine.
Thirty young (18–25) chronically sleep-restricted drivers drove in a simulator under randomized conditions of continuous bright light (‘Light,’ 500 nm, 230μw/cm2), caffeine (‘Caffeine,’ 100 mg caffeinated gum), or light and caffeine together (‘Light + Caffeine’), after driving under a placebo condition (‘Placebo,’ decaffeinated gum, 555 nm light, 0.3 μW/cm2) on three consecutive days. Using mixed-effects linear models, the associations between these conditions and physiological outcomes (EEG alpha and theta power, heart rate, and beat-to-beat intervals), driving performance (lateral lane and steering-related outcomes and lateral acceleration), and subjective sleepiness was assessed.
Relative to Placebo, all conditions improved driving performance outcomes (P < 0.0001), with effects of Light + Caffeine equal to Light but greater than Caffeine. Light + Caffeine reduced EEG alpha power more than Light or Caffeine (P < 0.0006), but ECG outcomes were generally worse under all conditions relative to Placebo. Subjective sleepiness improved under the Light + Caffeine condition only (P < 0.0001).
Combining bright light and caffeine enhances their alerting effects on lateral lane variability and subjective sleepiness. A bright light could be a practical alternative to caffeine for sleepy drivers who avoid caffeine. The alerting effects of bright light could alleviate chronic community-level mild sleep restriction and provide on-road benefits to reduce severe injuries and fatal sleepiness-related crashes.
•Light, Caffeine and Light + Caffeine improved driving performance outcomes.•Effects of Light + Caffeine on driving performance outcomes equated the Light.•Alerting effects of Light + Caffeine on mean and SD of lateral lane position were greater than Caffeine.•Physiological outcomes deteriorated under all conditions, except for a decrease of EEG theta activity with Light.•Only Light + Caffeine condition improved subjective sleepiness.
This systematic review aims to identify, evaluate, and summarise the consequences of precarious employment.
We included studies published within the last ten years (Jan 2011-July 2021) that employed ...at least two of three key dimensions of precarious employment: employment insecurity, income inadequacy, and lack of rights and protection.
Of the 4,947 initially identified studies, only five studies met our eligibility criteria. These five studies were of moderate quality as assessed by the Newcastle-Ottawa Scale. Our review found that the current literature predominantly defines precarity based on the single criterion of employment insecurity. Our review identified evidence for the negative consequences of precarious employment, including poorer workplace wellbeing, general health, mental health, and emotional wellbeing. The findings indicated an increase in the magnitude of these adverse outcomes with a higher degree of job precariousness.
The rise of employment precariousness will likely continue to be a major issue in the coming years. More research is needed to inform effective policies and practices using a consensus definition of precarious employment.
The presence of adverse effects of precarious employment suggests workplace initiatives are essential to mitigate the negative consequences of precarity.
Drowsiness leads to 20% of fatal road crashes, while inability to assess drowsiness has hampered drowsiness interventions. This study examined the accuracy of eye-blink parameters for detecting ...drowsiness related driving impairment in real time.
Twelve participants undertook two sessions of 2-hour track-driving in an instrumented vehicle following a normal night's sleep or 32 to 34 hours of extended wake in a randomized crossover design. Eye-blink parameters and lane excursion events were monitored continuously.
Sleep deprivation increased the rates of out-of-lane driving events and early drive terminations. Episodes of prolonged eyelid closures, blink duration, the ratio of amplitude to velocity of eyelid closure, and John's Drowsiness Score (JDS, a composite score) were also increased following sleep deprivation. A time-on-task (drive duration) effect was evident for out-of-lane events rate and most eye-blink parameters after sleep deprivation. The JDS demonstrated the strongest association with the odds of out-of-lane events in the same minute, whereas measures of blink duration and prolonged eye closure were stronger indicators of risk for out-of-lane events over longer periods of 5 minutes and 15 minutes, respectively. Eye-blink parameters also achieved moderate accuracies (specificities from 70.12% to 84.15% at a sensitivity of 50%) for detecting out-of-lane events in the same minute, with stronger associations over longer timeframes of 5 minutes to 15 minutes.
Eyelid closure parameters are useful tools for monitoring and predicting drowsiness-related driving impairment (out-of-lane events) that could be utilized for monitoring drowsiness and assessing the efficacy of drowsiness interventions.
This study is registered with the Australian New Zealand Clinical Trial Registry (ANCTR), http://www.anzctr.org.au/TrialSearch.aspx ACTRN12612000102875.
Drowsiness leads to 20% of fatal road crashes, while inability to assess drowsiness has hampered drowsiness interventions. This study examined the accuracy of eye-blink parameters for detecting ...drowsiness related driving impairment in real time.
Twelve participants undertook two sessions of 2-hour track-driving in an instrumented vehicle following a normal night's sleep or 32 to 34 hours of extended wake in a randomized crossover design. Eye-blink parameters and lane excursion events were monitored continuously.
Sleep deprivation increased the rates of out-of-lane driving events and early drive terminations. Episodes of prolonged eyelid closures, blink duration, the ratio of amplitude to velocity of eyelid closure, and John's Drowsiness Score (JDS, a composite score) were also increased following sleep deprivation. A time-on-task (drive duration) effect was evident for out-of-lane events rate and most eye-blink parameters after sleep deprivation. The JDS demonstrated the strongest association with the odds of out-of-lane events in the same minute, whereas measures of blink duration and prolonged eye closure were stronger indicators of risk for out-of-lane events over longer periods of 5 minutes and 15 minutes, respectively. Eye-blink parameters also achieved moderate accuracies (specificities from 70.12% to 84.15% at a sensitivity of 50%) for detecting out-of-lane events in the same minute, with stronger associations over longer timeframes of 5 minutes to 15 minutes.
Eyelid closure parameters are useful tools for monitoring and predicting drowsiness-related driving impairment (out-of-lane events) that could be utilized for monitoring drowsiness and assessing the efficacy of drowsiness interventions.
This study is registered with the Australian New Zealand Clinical Trial Registry (ANCTR), http://www.anzctr.org.au/TrialSearch.aspx ACTRN12612000102875.
Shekari Soleimanloo S, Wilkinson VE, Cori JM,Westlake J, Stevens B, Downey LA, Shiferaw BA, Rajaratnam SMW, Howard ME. Eye-blink parameters detect on-road track-driving impairment following severe sleep deprivation. J Clin Sleep Med. 2019;15(9):1271-1284.
•Ocular parameters (Johns Drowsiness Scores, JDS) could detect real-time drowsiness in HVDs on the road.•The risk of drowsiness in HVDs was measured by the occurrence of drowsiness events (JDS ≥ 2.6 ...events/hour) and assessed by logistic regression models.•Night-time drive, shift start time in the early afternoon, prolonged work hours, short break durations (7–9 h) and short sleep time (<6 h) increased the risk of drowsiness after controlling for the effects of other work schedule metrics.•The magnitude of driver drowsiness was measured using hourly rates of drowsiness events (JDS ≥ 2.6 events/hour) and assessed by mixed linear regression models.•Night-time drive, shift start time in the early morning, prolonged work hours, break times (<9 h), and shift of 8–15 h increased the hourly rate of drowsiness events after adjusting for the effects of other work schedules metrics.•Night-time drives (9 pm- 2 am), 18 to 21 h into the shift, or breaks shorter than 7 h elevated drowsiness event rates substantially relative to “alert state (4.9 events/hour) after controlling for the effects of other work schedule metrics.
While drowsiness contributes to 20% of heavy vehicle crashes, the impact of work schedules on heavy vehicle driver (HVD) drowsiness is unclear. This study explored the impact of work schedules on drowsiness (measured by infrared oculography) in HVDs.
Work and drowsiness monitoring (Optalert, Australia) of ten HVDs, aged 37–62 years collected nearly 2430 h of work and 1068 h of oculography data during four weeks of naturalistic drives. Drowsiness events were defined as a John's Drowsiness Scores ≥ 2.6. Nine HVDs slept for 5.82 ± 1.37 h during five weeks of actigraphy. Association of driving schedule characteristics and drivers’ continuous eye-blink parameters were observed using logistic and mixed linear regression analyses.
Combination of time of day (10 pm- 2 am), shift start time (2 pm-3 pm), hours into the shift (16–21 h), break duration (7–9 h), and sleep time (<6 h) increased the likelihood of drowsiness events when controlling for other covariates. A combination of night times (6 pm to 2 am), 18 to 21 h into the shift, shift start times (6 am to 7 am), shifts lengths (8 to15 h) and break times (<7 to 9 h) increased the hourly rate of drowsiness significantly when adjusting for other covariates.
The combination of prolonged work hours, night-time drives, early-morning shift starts and short breaks increase drowsiness rates in HVDs. Large datasets are needed to examine the interplay between sleep time, consecutive shifts and shift order and type with this combination.
•Heavy vehicle drivers on average had 5.1-hours sleep during a 7-hour rest break.•Heavy vehicle drivers on average had 6.5-hours sleep during an 11-hour rest break.•Subjective sleepiness was reduced ...after the 11- vs. 7-hour rest break.•Objective alertness when driving was improved after the 11- vs. 7-hour rest break.•Some driving performance metrics were improved after the 11- vs. 7-hour rest break.
An inadequate rest break between shifts may contribute to driver sleepiness. This study assessed whether extending the major rest break between shifts from 7-hours (Australian industry standard) to 11-hours, improved drivers’ sleep, alertness and naturalistic driving performance.
17 heavy vehicle drivers (16 male) were recruited to complete two conditions. Each condition comprised two 13-hour shifts, separated by either a 7- or 11-hour rest break. The initial 13-hour shift was the drivers’ regular work. The rest break and following 13-hour shift were simulated. The simulated shift included 5-hours of naturalistic driving with measures of subjective sleepiness, physiological alertness (ocular and electroencephalogram) and performance (steering and lane departures).
13 drivers provided useable data. Total sleep during the rest break was greater in the 11-hour than the 7-hour condition (median hours 25th to 75th percentile 6.59 6.23, 7.23 vs. 5.07 4.46, 5.38, p = 0.008). During the simulated shift subjective sleepiness was marginally better for the 11-hour condition (mean Karolinska Sleepiness Scale 95th CI = 4.52 3.98, 5.07 vs. 5.12 4.56, 5.68, p = 0.009). During the drive, ocular and vehicle metrics were improved for the 11-hour condition (p<0.05). Contrary to expectations, mean lane departures p/hour were increased during the 11-hour condition (1.34 −0.38,3.07 vs. 0.63 −0.2,1.47, p = 0.027).
Extending the major rest between shifts substantially increases sleep duration and has a modest positive impact on driver alertness and performance. Future work should replicate the study in a larger sample size to improve generalisability and assess the impact of consecutive 7-hour major rest breaks.
BackgroundCurrent evidence suggests that precarious employment is a risk factor for poor mental health. Although the mechanisms underpinning this relationship are unclear, poor sleep has been ...proposed to have a role in this relationship. This study explored the mediating effects of poor sleep quality and duration on the relationship between precarious employment and mental health.MethodsData were obtained from wave 17 of the Household, Income and Labour Dynamics in Australia survey. A novel precarious employment score (PES) was developed using exploratory and confirmatory factor analyses (CFA) in 8127 workers (4195 female, aged 18-65). Structural equation modelling (SEM) was used to evaluate the mediating effect of sleep quality and duration on the relationship between precarious employment and mental health (SF-36 mental health subscale).ResultsThe PES identified 650 workers with a high level of precariousness, 2417 with a moderate level of precariousness, and 5060 workers with a low level of precariousness out of 8127 in total. There was a significant direct association between precarious employment and mental health; with higher precarity increasing the likelihood of poor mental health. The SEM results revealed that sleep quality partially mediated the association between precarious employment and mental health (Coefficient = 0.025, 95 % CI 0.015, 0.034, P ≤ 0.001). However, a mediation effect was not found for sleep duration.ConclusionEncouraging precarious employees to improve sleep quality may mitigate the adverse effects of precarious work on their mental health. Further objective measurement of sleep duration warrants a more accurate insight into this mediating effect in this group.
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