The role of driver sleepiness in car crashes: a systematic review of epidemiological studies

The utility of automated measures of ocular metrics for detecting driver drowsiness during extended wakefulness

Slowed eyelid closure coupled with increased duration and frequency of closure is associated with drowsiness. This study assessed the utility of two devices for automated measurement of slow eyelid closure in a standard poor performance condition (alcohol) and following 12-h sleep deprivation. Twenty-two healthy participants (mean age=20.8 (SD 1.9) years) with no history of sleep disorders participated in the study. Participants underwent one baseline and one counterbalanced session each over two weeks; one 24-hour period of sleep deprivation, and one daytime session during which alcohol was consumed after a normal night of sleep. Participants completed a test battery consisting of a 30-min simulated driving task, a 10-min Psychomotor Vigilance Task (PVT) and the Karolinska Sleepiness Scale (KSS) each in two baseline sessions, and in two randomised, counterbalanced experimental sessions; following sleep deprivation and following alcohol consumption. Eyelid closure was measured during both tasks using two automated devices (Copilot and Optalert™). There was an increase in the proportion of time with eyelids closed and the Johns Drowsiness Score (incorporating relative velocity of eyelid movements) following sleep deprivation using Optalert (p<0.05 for both). These measures correlated significantly with crashes, PVT lapses and subjective sleepiness (r-values 0.46-0.69, p<0.05). No difference between the two sessions for PERCLOS recorded during the PVT or the driving task as measured by the Copilot. The duration of eyelid closure predicted frequent lapses following sleep deprivation (which were equivalent to the average lapses at a blood alcohol concentration of 0.05% - area under curve for ROC curve 0.87, p<0.01). The duration of time with slow eyelid closure, assessed by the automated devices, increased following sleep deprivation and was associated with deterioration in psychomotor performance and subjective sleepiness. Comprehensive algorithms inclusive of ocular parameters may be a better indicator of performance impairment following sleep loss.

Validation of the Driver Stress Inventory in China: Relationship with dangerous driving behaviors

Perceived stress while driving may affect how critical driving events are handled. The current study validates a Chinese version of the Driver Stress Inventory (DSI) and explores its correlation with dangerous driving behaviors and gender. A sample of 246 drivers completed the Chinese version of the DSI and the Driver Behavior Questionnaire (DBQ). We also evaluated specific sociodemographic variables and traffic violations (including speeding, violating traffic signs or markings, driving while intoxicated, running a red light, and incurring penalty points). A confirmatory factor analysis (CFA) verified the DSI's internal structure. The DSI was also validated using questionnaires related to the DBQ, self-reported traffic accidents and violations, and sociodemographic characteristics. First, all of the DSI dimensions were moderately or weakly correlated with the DBQ subscales. Second, aggression, hazard monitoring and fatigue were weakly correlated with minor accidents. Third, drivers who had sped and violated traffic signs during the previous three years reported higher aggression and thrill seeking, while drivers who had violated traffic signs or markings during the previous three years reported decreased hazard monitoring compared with non-offenders. Finally, there were significant gender differences in driver stress. The Chinese version of the DSI will be useful for classifying and diagnosing drivers who may be at an increased risk for stress reactions.

Attention Deficit Hyperactivity Disorder Symptoms, Sleepiness and Accidental Risk in 36140 Regularly Registered Highway Drivers

BACKGROUND

Attention Deficit Hyperactivity Disorder (ADHD) is a frequent neurodevelopmental disorder that increases accidental risk. Recent studies show that some patients with ADHD can also suffer from excessive daytime sleepiness but there are no data assessing the role of sleepiness in road safety in patients with ADHD. We conducted an epidemiological study to explore sleep complaints, inattention and driving risks among automobile drivers.

METHODS AND FINDINGS

From August to September 2014, 491186 regular highway users were invited to participate in an Internet survey on driving habits. 36140 drivers answered a questionnaire exploring driving risks, sleep complaints, sleepiness at the wheel, ADHD symptoms (Adult ADHD Self-Report Scale) and distraction at the wheel. 1.7% of all drivers reported inattention-related driving accidents and 0.3% sleep-related driving accidents in the previous year. 1543 drivers (4.3%) reported ADHD symptoms and were more likely to report accidents than drivers without ADHD symptoms (adjusted OR = 1.24, [1.03-1.51], p < .021). 14.2% of drivers with ADHD symptoms reported severe excessive daytime sleepiness (Epworth Sleepiness Scale >15) versus 3.2% of drivers without ADHD symptoms and 20.5% reported severe sleepiness at the wheel versus 7.3%. Drivers with ADHD symptoms reported significantly more sleep-related (adjusted OR = 1.4, [1.21-1.60], p < .0001) and inattention-related (adjusted OR = 1.9, [1.71-2.14], p<0001) near misses than drivers without ADHD symptoms. The fraction of near-misses attributable to severe sleepiness at the wheel was 4.24% for drivers without ADHD symptoms versus 10,35% for drivers with ADHD symptoms.

CONCLUSION

Our study shows that drivers with ADHD symptoms have more accidents and a higher level of sleepiness at the wheel than drivers without ADHD symptoms. Drivers with ADHD symptoms report more sleep-related and inattention-related near misses, thus confirming the clinical importance of exploring both attentional deficits and sleepiness at the wheel in these drivers. Road safety campaigns should be improved to better inform drivers of these accidental risks.

Sleep Deprivation Is Associated with Bicycle Accidents and Slip and Fall Injuries in Korean Adolescents

Objective

This study sought to evaluate associations between sleep time and bicycle accidents, falls under various circumstances, and dental injuries in adolescents.

Methods

A total of 61,696 participants ranging from 12 to 18 years of age who completed the Korea Youth Risk Behavior Web-based Survey (KYRBWS) in 2013 were enrolled in this study. Bicycle riding accidents were analyzed for 17,232 bicycle-riding participants. Data were collected regarding the weekday sleep duration for the most recent 7 days, which was categorized as < 5.5 h, 5.5–6.5 h, 6.5–7.5 h, or ≥ 7.5 h per day, and the incidence of bicycle accidents, slips and falls under various circumstances, and dental injuries in the most recent 12 months. Adjusted odds ratios (aORs) were calculated among sleep groups for bicycle accidents, slips and falls, and dental injuries using simple and multiple logistic regression analyses with complex sampling.

Results

Bicycle riding accidents and slips and falls in classrooms, corridors, the ground, toilets, stairs, and other unspecified situations showed positive correlations with sleep deprivation. Comparisons of groups with ≥ 7.5 h sleep, < 5.5 h, 5.5–6.5 h sleep, and 6.5–7.5 h sleep revealed increased associations with slips and falls under various circumstances. In particular, the aORs were higher in the groups with less sleep (aOR of the 5.5 h group > the 5.5–6.5 h group > the 6.5–7.5 h group). There was no significant relationship between sleep deprivation and dental injury.

Conclusions

This study demonstrated that sleep deprivation among Korean adolescents was associated with bicycle accidents and falls at home and school. Thus, adequate sleep may be needed to prevent accidents and falls.

Sleep-related factors and work-related injuries among farmers in Heilongjiang Province, People's Republic of China

The association between sleep and work-related injuries among Chinese farmers has not been well studied. This study examined the impact of lack of sleep on agricultural work-related injuries among farmers in China. Data were from a cross-sectional survey of farm-workers in northeastern China. Information was obtained on injuries that occurred in 12 months prior to the survey, on eight sleep-related variables, and on socio-demographic variables. Logistic regression analyses were conducted to test the hypothesis that lack of sleep significantly increased the risk of work-related injuries after controlling for other injury-related risk- factors. Farmers who slept less than six hours per night were 59% more likely to be injured than those who slept more than eight hours per night (OR = 1.59; 95% CI = 1.04, 2.41). The odds of a work-related injury was 2.46 (1.56–3.89) for farmers who reported going to sleep after midnight at least once a week compared with farmers who reported going to sleep after midnight once a month. Farmers who reported having difficulty falling asleep or waking frequently during the night, who often having nightmares, or who experienced daytime sleepiness were at higher injury risk compared with the reference group after controlling for age, gender and alcohol consumption. Reduced sleep hours and poor sleep quality significantly increased the risk of work-related injuries in Chinese farmers. Sleep hours and sleep quality should be considered when assessing occupational safety among farmers.

Inhibition of return, but not facilitation, disappears under vigilance decrease due to sleep deprivation

In this study, we assessed whether unspecific attention processes signaled by general reaction times (RTs), as well as specific facilitatory (validity or facilitation effect) and inhibitory (inhibition of return, IOR) effects involved in the attentional orienting network, are affected by low vigilance due to both circadian factors and sleep deprivation (SD). Eighteen male participants performed a cuing task in which peripheral cues were nonpredictive about the target location and the cue-target interval varied at three levels: 200 ms, 800 ms, and 1,100 ms. Facilitation with the shortest and IOR with the longest cue-target intervals were observed in the baseline session, thus replicating previous related studies. Under SD condition, RTs were generally slower, indicating a reduction in the participants' arousal level. The inclusion of a phasic alerting tone in several trials partially compensated for the reduction in tonic alertness, but not with the longest cue-target interval. With regard to orienting, whereas the facilitation effect due to reflexive shifts of attention was preserved with sleep loss, the IOR was not observed. These results suggest that the decrease of vigilance produced by SD affects both the compensatory effects of phasic alerting and the endogenous component involved in disengaging attention from the cued location, a requisite for the IOR effect being observed.

Insufficient sleep in adolescents and young adults: an update on causes and consequences

Chronic sleep loss and associated sleepiness and daytime impairments in adolescence are a serious threat to the academic success, health, and safety of our nation's youth and an important public health issue. Understanding the extent and potential short- and long-term repercussions of sleep restriction, as well as the unhealthy sleep practices and environmental factors that contribute to sleep loss in adolescents, is key in setting public policies to mitigate these effects and in counseling patients and families in the clinical setting. This report reviews the current literature on sleep patterns in adolescents, factors contributing to chronic sleep loss (ie, electronic media use, caffeine consumption), and health-related consequences, such as depression, increased obesity risk, and higher rates of drowsy driving accidents. The report also discusses the potential role of later school start times as a means of reducing adolescent sleepiness.

Evaluation of candidate measures for home-based screening of sleep disordered breathing in Taiwanese bus drivers

Background: Sleepiness-at-the-wheel has been identified as a major cause of highway accidents. The aim of our study is identifying the candidate measures for home-based screening of sleep disordered breathing in Taiwanese bus drivers, instead of polysomnography. Methods: Overnight polysomnography accompanied with simultaneous measurements of alternative screening devices (pulse oximetry, ApneaLink, and Actigraphy), heart rate variability, wake-up systolic blood pressure and questionnaires were completed by 151 eligible participants who were long-haul bus drivers with a duty period of more than 12 h a day and duty shifting. Results: 63.6% of professional bus drivers were diagnosed as having sleep disordered breathing and had a higher body mass index, neck circumference, systolic blood pressure, arousal index and desaturation index than those professional bus drivers without evidence of sleep disordered breathing. Simple home-based candidate measures: (1) Pulse oximetry, oxygen-desaturation indices by ≥3% and 4% (r = 0.87∼0.92); (2) Pulse oximetry, pulse-rising indices by ≥7% and 8% from a baseline (r = 0.61∼0.89); and (3) ApneaLink airflow detection, apnea-hypopnea indices (r = 0.70∼0.70), based on recording-time or Actigraphy-corrected total sleep time were all significantly correlated with, and had high agreement with, corresponding polysomnographic apnea-hypopnea indices [(1) 94.5%∼96.6%, (2) 93.8%∼97.2%, (3) 91.1%∼91.3%, respectively]. Conversely, no validities of SDB screening were found in the multi-variables apnea prediction questionnaire, Epworth Sleepiness Scale, night-sleep heart rate variability, wake-up systolic blood pressure and anthropometric variables. Conclusions: The indices of pulse oximetry and apnea flow detection are eligible criteria for home-based screening of sleep disordered breathing, specifically for professional drivers.

Poor vigilance affects attentional orienting triggered by central uninformative gaze and arrow cues

Behaviour and neuroimaging studies have shown that poor vigilance (PV) due to sleep deprivation (SD) negatively affects exogenously cued selective attention. In the current study, we assessed the impact of PV due to both partial SD and night-time hours on reflexive attentional orienting triggered by central un-informative eye-gaze and arrow cues. Subjective mood and interference performance in emotional Stroop task were also investigated. Twenty healthy participants performed spatial cueing tasks using central directional arrow and eye-gaze as a cue to orient attention. The target was a word written in different coloured inks. The participant's task was to identify the colour of the ink while ignoring the semantic content of the word (with negative or neutral emotional valence). The experiment took place on 2 days. On the first day, each participant performed a 10-min training session of the spatial cueing task. On the second day, half of participants performed the task once at 4:30 p.m. (BSL) and once at 6:30 a.m. (PV), whereas the other half performed the task in the reversed order. Results showed that mean reaction times on the spatial cueing tasks were worsened by PV, although gaze paradigm was more resistant to this effect as compared to the arrow paradigm. Moreover, PV negatively affects attentional orienting triggered by both central un-informative gaze and arrow cues. Finally, prolonged wakefulness affects self-reported mood but does not influence interference control in emotional Stroop task.

Modafinil improves real driving performance in patients with hypersomnia: a randomized double-blind placebo-controlled crossover clinical trial

STUDY OBJECTIVE

Patients with excessive daytime sleepiness (EDS) are at high risk for driving accidents, and physicians are concerned by the effect of alerting drugs on driving skills of sleepy patients. No study has up to now investigated the effect of modafinil (a reference drug to treat EDS in patients with hypersomnia) on on-road driving performance of patients suffering from central hypersomnia. The objective is to evaluate in patients with central hypersomnia the effect of a wake-promoting drug on real driving performance and to assess the relationship between objective sleepiness and driving performance.

DESIGN AND PARTICIPANTS

Randomized, crossover, double-blind placebo-controlled trial conducted among 13 patients with narcolepsy and 14 patients with idiopathic hypersomnia. Patients were randomly assigned to receive modafinil (400 mg) or placebo for 5 days prior to the driving test. Each condition was separated by at least 3 weeks of washout.

MEASUREMENTS

Mean number of Inappropriate Line Crossings, Standard Deviation of Lateral Position of the vehicle and mean sleep latency in the Maintenance of Wakefulness Test were assessed.

RESULTS

Modafinil reduced the mean number of Inappropriate Line Crossings and Standard Deviation of Lateral Position of the vehicle compared to placebo (F(1,25) = 4.88, P < 0.05 and F(1,25) = 3.87, P = 0.06 tendency). Mean sleep latency at the Maintenance of Wakefulness Test significantly correlated with the mean number of Inappropriate Line Crossings (r = -0.41, P < 0.001).

CONCLUSIONS

Modafinil improves driving performance in patients with narcolepsy and idiopathic hypersomnia. The Maintenance of Wakefulness Test is a suitable clinical tool to assess fitness to drive in this population.

The Association between Sleep and Injury among School-Aged Children in Iran

Background. A good night's sleep plays a key role in diseases resistance, injury prevention, and mood stability. The objective of this study was to examine relationship between sleep problems and accidental injury occurrences in school-aged children. Method. A retrospective study was conducted for comparing two groups of children. Children who have experienced injuries for at least two times during an academic year are the participants in the injury group (IG) and those who have not experienced any kind of injuries are placed in the noninjury group (NIG). Data was collected through parent-reported sleep patterns and problems using Children's Sleep Habits Questionnaire (CSHQ). Findings. The findings showed that global sleep problems were more in the IG than in the NIG. Multivariate logistic regression analysis showed that the daytime sleepiness and sleep duration are the two major reasons for accidental injury. In addition, significant difference was seen between the sleep patterns of the two groups. Sleep duration was also shorter in the IG, and this group had a greater percentage (63% versus 41.1%) of “short sleepers” (<9 h). Conclusion. There is a significant relationship between injury occurrence and sleep problems and sleep duration in Iranian school-aged children.

Maintenance of Wakefulness Test scores and driving performance in sleep disorder patients and controls

OBJECTIVE

Sleepiness at the wheel is a risk factor for traffic accidents. Past studies have demonstrated the validity of the Maintenance of Wakefulness Test (MWT) scores as a predictor of driving impairment in untreated patients with obstructive sleep apnea syndrome (OSAS), but there is limited information on the validity of the maintenance of wakefulness test by MWT in predicting driving impairment in patients with hypersomnias of central origin (narcolepsy or idiopathic hypersomnia). The aim of this study was to compare the MWT scores with driving performance in sleep disorder patients and controls.

METHODS

19 patients suffering from hypersomnias of central origin (9 narcoleptics and 10 idiopathic hypersomnia), 17 OSAS patients and 14 healthy controls performed a MWT (4×40-minute trials) and a 40-minute driving session on a real car driving simulator. Participants were divided into 4 groups defined by their MWT sleep latency scores. The groups were pathological (sleep latency 0-19 min), intermediate (20-33 min), alert (34-40 min) and control (>34 min). The main driving performance outcome was the number of inappropriate line crossings (ILCs) during the 40 minute drive test.

RESULTS

Patients with pathological MWT sleep latency scores (0-19 min) displayed statistically significantly more ILC than patients from the intermediate, alert and control groups (F (3, 46)=7.47, p<0.001).

INTERPRETATION

Pathological sleep latencies on the MWT predicted driving impairment in patients suffering from hypersomnias of central origin as well as in OSAS patients. MWT is an objective measure of daytime sleepiness that appears to be useful in estimating the driving performance in sleepy patients.

Sleep problems and work injuries: a systematic review and meta-analysis

OBJECTIVES

Sleep problems are a potential risk factor for work injuries but the extent of the risk is unclear. We conducted a systematic review and meta-analysis to quantify the effect of sleep problems on work injuries.

METHODS

A systematic literature search using several databases was performed. Sleep problems of any duration or frequency as well as work injuries of any severity were of interest. The effect estimates of the individual studies were pooled and relative risks (RR) and 95% confidence intervals (CI) were calculated through random effects models. Additionally, the population attributable risk was estimated.

RESULTS

In total, 27 observational studies (n = 268,332 participants) that provided 54 relative risk estimates were included. The findings of the meta-analysis suggested that workers with sleep problems had a 1.62 times higher risk of being injured than workers without sleep problems (RR: 1.62, 95% CI: 1.43-1.84). Approximately 13% of work injuries could be attributed to sleep problems.

CONCLUSION

This systematic review confirmed the association between sleep problems and work injuries and, for the first time, quantified its magnitude. As sleep problems are of growing concern in the population, these findings are of interest for both sleep researchers and occupational physicians.

The contributions of sleep-related risk factors to diurnal car accidents

This study was intended to estimate the presence and number of individual sleep-related risk factors in a sample of diurnal car accidents and to analyze the extent to which these risk factors tended to be more represented in diurnal accidents involving only one vehicle, involving young drivers or occurring on non-urban roads. Two hundred fifty-three drivers involved in diurnal accidents were interviewed immediately after the accidents to assess their sleepiness-related personal conditions and the circumstances prior to the accident (i.e., individual sleep-related risk factors), such as poor sleep, changes in habitual sleeping patterns, prolonged wakefulness, self-reported acute sleepiness and daytime sleepiness, night-shift jobs and insomnia. A total of 12.3% of the drivers were classified as having at least one of the seven risk factors assessed in the study, supporting the general notion that drivers' sleepiness conditions are crucial, even in diurnal driving circumstances in which they are less likely to depend on chrono-biological processes. Furthermore, consistent with the guiding hypotheses, specific sleep-related risk factors were more evident in single (vs. multiple) car accidents, among young drivers and in car accidents occurring on non-urban roads. In summary, sleep-related risk factors seemed to have a negative impact on drivers' safety in circumstances of diurnal driving, especially when the accidents involved young individuals and occurred on non-urban roads.

A case-control study on excessive daytime sleepiness in chronic migraine

BACKGROUND

Excessive daytime sleepiness is a major clinical and health concern that can have varied and sometimes harmful consequences. Findings from uncontrolled studies suggest a high prevalence in patients with chronic migraine.

METHODS

In a case-control study, we compared frequency data for excessive daytime sleepiness in 100 patients with chronic migraine and 100 healthy controls paired for sex and age, and assessed risk factors including lifestyle, sleep quality, anxiety, depression, concomitant disease and medications.

RESULTS

The frequency of excessive daytime sleepiness was higher in migraineurs (especially in those with medication overuse) than in controls (20% versus 6%; odds ratio 3.92, 95% CI 1.5-10.22), but was lower than previously reported and correlated with poor quality sleep and anxiolytic and antidepressant use.

CONCLUSIONS

Again confirming that disability in chronic migraine is multifactorial in origin, excessive daytime sleepiness, especially in migraineurs who overuse medications, adds to the multiple factors known to impair social and working function. Patients with chronic migraine might benefit from diagnostic interviews focussing also on sleep problems and from targeted psychoactive drug prescribing.

Psychomotor performance of truck drivers before and after day shifts

OBJECTIVE

The aim of the present study is to evaluate the psychomotor performance of professional drivers in a field setting and in relation to certain variables, including age, behavioral factors, urinary levels of 6-sulfatoxymelatonin (aMT6s) normalized to urinary creatinine excretion, and the characteristics of the work shifts.

METHODS

The study was carried out on 16 professional male truck drivers aged 34-53 years. The drivers were submitted to the Vienna Reaction Test (RT) and Vienna Determination Test (DT) and provided urine specimens before and after 39 work shifts. They were also asked to record the road and traffic conditions (motorways, suburban and urban roads, traffic jams, visibility), duration, and mileage for each driving shift.

RESULTS

Using the 50th percentile as a cut point to arbitrarily categorize the performance measurements (Vienna RT reaction time and motor time, Vienna DT reaction time and number of correct reactions) into low and high performance levels, a direct relation emerged between the risk of low performance levels, as assessed by RT reaction time and motor time, and morning urinary levels of aMT6s categorized by tertiles. Before the driving shifts, the odds ratios of low performance levels (adjusted for start time and age) were 8.39 (95% confidence interval [CI]: 1.23-57.10) in the highest tertile compared to the lower tertile of aMT6s for RT reaction time and 4.15 (95% CI: 1.26-13.65) for RT motor time, respectively. After driving shifts, negative age-related effects on motor performance were detected. Multiple linear regression analyses, performed using early morning urinary aMT6s levels, age, and driving shift characteristics (start time, duration of driving shift) as predictors of performance measurements, showed aMT6s levels to be the primary independent predictor of RT reaction time before driving shifts and age as the primary predictor of RT motor time after driving shifts. No correlation was found between the risk of low performance levels as assessed by Vienna DT (reaction time and number of correct reactions) and aMT6s levels.

CONCLUSIONS

The wide interindividual variability of urinary aMT6s excretion observed before driving shifts and the direct association between aMT6s levels in the early morning and performance measurements suggest that the circadian typology of drivers should be taken into account when scheduling the work shifts of professional drivers.

Wireless-based portable EEG-EOG monitoring for real time drowsiness detection

Drowsiness is one of the major risk factors causing accidents that result in a large number of damage. Drivers and industrial workers probably have a large effect on several mishaps occurring from drowsiness. Therefore, advanced technology to reduce these accidental rates is a very challenging problem. Nowadays, there have been many drowsiness detectors using electroencephalogram (EEG), however, the cost is still high and the use of this is uncomfortable in long-term monitoring because most of them require wiring and conventional wet electrodes. The purpose of this paper is to develop a portable wireless device that can automatically detect the drowsiness in real time by using the EEG and electrooculogram (EOG). The silver (Ag) conducting fabric consolidated in a headband used as dry electrodes can acquire signal from the user's forehead. The signal was sent via the wireless communication of XBee® 802.15.4 to a standalone microcontroller to analyze drowsiness using the proposed algorithm. The alarm will ring when the drowsiness occurs. Besides, the automatic drowsiness detection and alarm device yields the real-time detection accuracy of approximately 81%.

Cognitive components of simulated driving performance: Sleep loss effects and predictors

Driving is a complex task, which can be broken down into specific cognitive processes. In order to determine which components contribute to drowsy driving impairments, the current study examined simulated driving and neurocognitive performance after one night of sleep deprivation. Nineteen professional drivers (age 45.3±9.1) underwent two experimental sessions in randomised order: one after normal sleep and one after 27h total sleep deprivation. A simulated driving task (AusEd), the psychomotor vigilance test (PVT), and neurocognitive tasks selected from the Cognitive Drug Research computerised neurocognitive assessment battery (simple and choice RT, Stroop Task, Digit Symbol Substitution Task, and Digit Vigilance Task) were administered at 10:00h in both sessions. Mixed-effects ANOVAs were performed to examine the effect of sleep deprivation versus normal sleep on performance measures. To determine if any neurocognitive tests predicted driving performance (lane position variability, speed variability, braking RT), neurocognitive measures that were significantly affected by sleep deprivation were then added as a covariate to the ANOVAs for driving performance. Simulated driving performance and neurocognitive measures of vigilance and reaction time were impaired after sleep deprivation (p<0.05), whereas tasks examining processing speed and executive functioning were not significantly affected by sleep loss. PVT performance significantly predicted specific aspects of simulated driving performance. Thus, psychomotor vigilance impairment may be a key cognitive component of driving impairment when sleep deprived. The generalisability of this finding to real-world driving remains to be investigated.

Driving behaviors and on-duty road accidents: a French case-control study

OBJECTIVES

A case-control study was carried out to identify driving behaviors associated with the risk of on-duty road accident and to compare driving behaviors according to the type of journey (on duty, commuting, and private) for on-duty road accident victims.

METHODS

Cases were recruited from the Rhône Road Trauma Registry between January 2004 and October 2005 and were on duty at the time of the accident. Control subjects were recruited from the electoral rolls of the case subjects' constituencies of residence. Cases' and controls' driving behavior data were collected by self-administered questionnaire. A logistic regression was performed to identify behavioral risk factors for on-duty road accidents, taking into account age, sex, place of residence, road accident risk exposure, socio-occupational category, and type of road user. A second analysis focused specifically on the case subjects, comparing their self-assessed usual behaviors according to the type of journey.

RESULTS

Significant factors for multivariate analysis of on-duty road accidents were female gender, history of on-duty road accidents during the previous 10 years, severe time pressure at work, and driving a vehicle not belonging to the driver. On-duty road accident victims reported behavioral risk factors more frequently in relation to driving for work than driving for private reasons or commuting: nonsystematic seat belt use, cell phone use at least once daily while driving, and history of accidents with injury during the previous 10 years.

CONCLUSIONS

This study provides knowledge on behavioral risk factors for on-duty road accidents and differences in behavior according to the type of journey for subjects who have been on-duty road accident victims. These results will be useful for the design of on-duty road risk prevention.

Measuring neurophysiological signals in aircraft pilots and car drivers for the assessment of mental workload, fatigue and drowsiness

This paper reviews published papers related to neurophysiological measurements (electroencephalography: EEG, electrooculography EOG; heart rate: HR) in pilots/drivers during their driving tasks. The aim is to summarise the main neurophysiological findings related to the measurements of pilot/driver's brain activity during drive performance and how particular aspects of this brain activity could be connected with the important concepts of "mental workload", "mental fatigue" or "situational awareness". Review of the literature suggests that exists a coherent sequence of changes for EEG, EOG and HR variables during the transition from normal drive, high mental workload and eventually mental fatigue and drowsiness. In particular, increased EEG power in theta band and a decrease in alpha band occurred in high mental workload. Successively, increased EEG power in theta as well as delta and alpha bands characterise the transition between mental workload and mental fatigue. Drowsiness is also characterised by increased blink rate and decreased HR values. The detection of such mental states is actually performed "offline" with accuracy around 90% but not online. A discussion on the possible future applications of findings provided by these neurophysiological measurements in order to improve the safety of the vehicles will be also presented.

Independent effects of sleep duration and body mass index on the risk of a work-related injury: evidence from the US National Health Interview Survey (2004-2010)

Fatigue has been linked to adverse safety outcomes, and poor quality or decreased sleep has been associated with obesity (higher body mass index, BMI). Additionally, higher BMI is related to an increased risk for injury; however, it is unclear whether BMI modifies the effect of short sleep or has an independent effect on work-related injury risk. To answer this question, the authors examined the risk of a work-related injury as a function of total daily sleep time and BMI using the US National Health Interview Survey (NHIS). The NHIS is an in-person household survey using a multistage, stratified, clustered sample design representing the US civilian population. Data were pooled for the 7-yr survey period from 2004 to 2010 for 101 891 "employed" adult subjects (51.7%; 41.1 ± yrs of age [mean ± SEM]) with data on both sleep and BMI. Weighted annualized work-related injury rates were estimated across a priori defined categories of BMI: healthy weight (BMI: <25), overweight (BMI: 25-29.99), and obese (BMI: ≥30) and also categories of usual daily sleep duration: <6, 6-6.99, 7-7.99, 8-8.99, and ≥9 h. To account for the complex sampling design, including stratification, clustering, and unequal weighting, weighted multiple logistic regression was used to estimate the risk of a work-related injury. The initial model examined the interaction among daily sleep duration and BMI, controlling for weekly working hours, age, sex, race/ethnicity, education, type of pay, industry, and occupation. No significant interaction was found between usual daily sleep duration and BMI (p = .72); thus, the interaction term of the final logistic model included these two variables as independent predictors of injury, along with the aforementioned covariates. Statistically significant covariates (p ≤ .05) included age, sex, weekly work hours, occupation, and if the worker was paid hourly. The lowest categories of usual sleep duration (<6 and 6-6.9 h) showed significantly (p ≤ .05) elevated injury risks than the referent category (7-8 h sleep), whereas sleeping >7-8 h did not significantly elevate risk. The adjusted injury risk odds ratio (OR) for a worker with a usual daily sleep of <6 h was 1.86 (95% confidence interval [CI]: 1.37-2.52), and for 6-6.9 h it was 1.46 (95% CI: 1.18-1.80). With regards to BMI, the adjusted injury risk OR comparing workers who were obese (BMI: ≥30) to healthy weight workers (BMI: <25) was 1.34 (95% CI: 1.09-1.66), whereas the risk in comparing overweight workers (BMI: 25-29.99) to healthy weight risk was elevated, but not statistically significant (OR = 1.08; 95% CI: .88-1.33). These results from a large representative sample of US workers suggest increase in work-related injury risk for reduced sleep regardless of worker's body mass. However, being an overweight worker also increases work-injury risk regardless of usual daily sleep duration. The independent additive risk of these factors on work-related injury suggests a substantial, but at least partially preventable, risk.

Sleep: a health imperative

Chronic sleep deficiency, defined as a state of inadequate or mistimed sleep, is a growing and underappreciated determinant of health status. Sleep deprivation contributes to a number of molecular, immune, and neural changes that play a role in disease development, independent of primary sleep disorders. These changes in biological processes in response to chronic sleep deficiency may serve as etiological factors for the development and exacerbation of cardiovascular and metabolic diseases and, ultimately, a shortened lifespan. Sleep deprivation also results in significant impairments in cognitive and motor performance which increase the risk of motor vehicle crashes and work-related injuries and fatal accidents. The American Academy of Sleep Medicine and the Sleep Research Society have developed this statement to communicate to national health stakeholders the current knowledge which ties sufficient sleep and circadian alignment in adults to health.

Assessing sleepiness and sleep disorders in Australian long-distance commercial vehicle drivers: self-report versus an "at home" monitoring device

STUDY OBJECTIVES

As obstructive sleep apnea (OSA) is associated with a higher risk of motor vehicle crashes, there is increasing regulatory interest in the identification of commercial motor vehicle (CMV) drivers with this condition. This study aimed to determine the relationship between subjective versus objective assessment of OSA in CMV drivers.

DESIGN

Cross-sectional survey.

SETTINGS

Heavy vehicle truck stops located across the road network of 2 large Australian states.

PARTICIPANTS

A random sample of long distance commercial vehicle drivers (n = 517).

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Drivers were interviewed regarding their driving experience, personal health, shift schedules, payments, and various questions on sleep and tiredness in order to describe their sleep health across a range of variables. In addition, home recordings using a flow monitor were used during one night of sleep. Only 4.4% of drivers reported a previous diagnosis of sleep apnea, while our at home diagnostic test found a further 41% of long-distance heavy vehicle drivers likely to have sleep apnea. The multivariable apnea prediction index, based on self-report measures, showed poor agreement with the home-monitor detected sleep apnea (AUC 0.58, 95%CI = 0.49-0.62), and only 12% of drivers reported daytime sleepiness (Epworth Sleepiness Scale score > 10). Thirty-six percent of drivers were overweight and a further 50% obese; 49% of drivers were cigarette smokers.

CONCLUSIONS

Sleep apnea remains a significant and unrecognized problem in CMV drivers, who we found to have multiple health risks. Objective testing for this sleep disorder needs to be considered, as symptom reports and self-identification appear insufficient to accurately identify those at risk.

Rumble strips in centre of the lane and the effect on sleepy drivers

The aim of this study was to describe the effects of sleep loss on behavioural and subjective indicators of sleepiness on a road containing a milled rumble strip in the centre of the lane. Particular attention was paid to behavioural and subjective indicators of sleepiness when using the centre lane rumble strip, and to possible erratic driving behaviour when hitting a rumble strip. In total 9 regular shift workers drove during the morning hours after a full night shift and after a full night sleep. The order was balanced. The experiment was conducted in a moving base driving simulator on rural roads with a road width of 6.5 and 9 meters. Out of the 1,636 rumble strip hits that occurred during the study, no indications of erratic driving behaviour associated with the jolt caused by making contact with the centre lane rumble strip could be found. Comparing the alert condition with the sleep deprived condition, both the standard deviation of lateral position (SDLP) and the Karolinska Sleepiness Scale (KSS) increased for sleepy drivers. For the two road widths, the drivers drove closer to the centre line on the 6.5-meter road. The KSS and the SDLP increased with time on task. This simulator study indicates that rumble strips in the centre of the lane may be an alternative to centreline and edgeline rumble strips on narrow roads.

Compliance to continuous positive airway pressure therapy in a group of Portuguese patients with obstructive sleep apnea syndrome

INTRODUCTION

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is an emerging public health concern. Although different treatments for OSAHS had been proposed, continuous positive airway pressure (CPAP) is the first-line treatment in moderate to serious OSAHS in which success can be achieved by increasing compliance to CPAP.

MATERIALS AND METHODS

This study analyzes long-term CPAP compliance in patients with OSAHS on CPAP therapy for at least 1 month, who began CPAP therapy between January 2004 and December 2006, followed up at a Portuguese Sleep Outpatient Clinic in Santo António Hospital. Only effective data of CPAP use had been considered. During the first year of CPAP therapy, 96 patients were enrolled and followed up, but 15 patients had discontinued CPAP treatment. CPAP was used on average 5.1 h per day and in 80.1% of the total follow-up days. When compliance is defined as the use of CPAP for a minimum of 4 h per day in at least 70% of the follow-up days, only 54% of patients were classified as compliants during the first year.

RESULTS AND CONCLUSION

No statistically significant differences were found throughout the first year (p > 0.05) in terms of the percentage of compliants, controlling for demographic and clinic variables. None of the demographic and clinical baseline variables studied were found to be significant predictor of CPAP compliance (p > 0.05). This study diagnosed a low compliance to CPAP therapy in the studied sample, warning to the need of developing further studies in this area and to the need of implementing strategies to increase CPAP compliance.

Alerting, orienting and executive control: the effects of sleep deprivation on attentional networks

Sleep deprivation alters attentional functions like vigilance or tonic alerting (i.e., sustaining an alert state over a period of time). However, the effects of sleep loss on both orienting and executive control are still not clear, and no study has assessed whether sleep deprivation might affect the relationships among these three attentional systems. In order to investigate the efficiency of the three attentional networks--alerting, orienting and executive control--within a single task, we used the Attention Network Test (ANT). Eighteen right-handed male participants took part in the experiment, which took place on two consecutive days. On the first day, each participant performed a 20 min training session of the ANT. On the second day, participants remained awake for 24 h during which time the ANT was performed once at 5:00 p.m. and once at 4:00 a.m. Results showed an overall slowing of reaction times in the nocturnal session, indicating a strong decrease in vigilance. Furthermore, sleep deprivation did affect attentional orienting and executive control. Results are consistent with the hypothesis that the tonic component of alerting interacts with both attentional orienting and executive functions.

The link between fatigue and safety

The objective of this review was to examine the evidence for the link between fatigue and safety, especially in transport and occupational settings. For the purposes of this review fatigue was defined as 'a biological drive for recuperative rest'. The review examined the relationship between three major causes of fatigue - sleep homeostasis factors, circadian influences and nature of task effects - and safety outcomes, first looking at accidents and injury and then at adverse effects on performance. The review demonstrated clear evidence for sleep homeostatic effects producing impaired performance and accidents. Nature of task effects, especially tasks requiring sustained attention and monotony, also produced significant performance decrements, but the effects on accidents and/or injury were unresolved because of a lack of studies. The evidence did not support a direct link between circadian-related fatigue influences and performance or safety outcomes and further research is needed to clarify the link. Undoubtedly, circadian variation plays some role in safety outcomes, but the evidence suggests that these effects reflect a combination of time of day and sleep-related factors. Similarly, although some measures of performance show a direct circadian component, others would appear to only do so in combination with sleep-related factors. The review highlighted gaps in the literature and opportunities for further research.

Sleep disorders, medical conditions, and road accident risk

Sleep disorders and various common acute and chronic medical conditions directly or indirectly affect the quality and quantity of one's sleep or otherwise cause excessive daytime fatigue. This article reviews the potential contribution of several prevalent medical conditions - allergic rhinitis, asthma, chronic obstructive pulmonary disease, rheumatoid arthritis/osteoarthritis - and chronic fatigue syndrome and clinical sleep disorders - insomnia, obstructive sleep apnea, narcolepsy, periodic limb movement of sleep, and restless legs syndrome - to the risk for drowsy-driving road crashes. It also explores the literature on the cost-benefit of preventive interventions, using obstructive sleep apnea as an example. Although numerous investigations have addressed the impact of sleep and medical disorders on quality of life, few have specifically addressed their potential deleterious effect on driving performance and road incidents. Moreover, since past studies have focused on the survivors of driver crashes, they may be biased. Representative population-based prospective multidisciplinary studies are urgently required to clarify the role of the fatigue associated with common ailments and medications on traffic crash risk of both commercial and non-commercial drivers and to comprehensively assess the cost-effectiveness of intervention strategies.

Daily sleep, weekly working hours, and risk of work-related injury: US National Health Interview Survey (2004-2008)

The impact on health and safety of the combination of chronic sleep deficits and extended working hours has received worldwide attention. Using the National Health Interview Survey (NHIS), an in-person household survey using a multistage, stratified, clustered sample design representing the US civilian, non-institutionalized population, the authors estimated the effect of total daily self-reported sleep time and weekly working hours on the risk of a work-related injury. During the survey period 2004-2008, 177,576 persons (ages 18-74) sampled within households reported that they worked at a paid job the previous week and reported their total weekly work hours. A randomly selected adult in each household (n = 75,718) was asked to report his/her usual (average) total daily sleep hours the prior week; complete responses were obtained for 74,415 (98.3%) workers. Weighted annualized work-related injury rates were then estimated across a priori defined categories of both average total daily sleep hours and weekly working hours. To account for the complex sampling design, weighted multiple logistic regression was used to independently estimate the risk of a work-related injury for categories of usual daily sleep duration and weekly working hours, controlling for important covariates and potential confounders of age, sex, race/ethnicity, education, type of pay, industry, occupation (proxy for job risk), body mass index, and the interaction between sleep duration and work hours. Based on the inclusion criteria, there were an estimated 129,950,376 workers annually at risk and 3,634,446 work-related medically treated injury episodes (overall injury rate 2.80/100 workers). Unadjusted annualized injury rates/100 workers across weekly work hours were 2.03 (< or =20 h), 3.01 (20-30 h), 2.45 (31-40 h), 3.45 (40-50 h), 3.71 (50-60 h), and 4.34 (>60 h). With regards to self-reported daily sleep time, the estimated annualized injury rates/100 workers were 7.89 (<5 h sleep), 5.21 (5-5.9 h), 3.62 (6-6.9 h), 2.27 (7-7.9 h), 2.50 (8-8.9 h), 2.22 (9-9.9 h), and 4.72 (>10 h). After controlling for weekly work hours, and aforementioned covariates, significant increases in risk/1 h decrease were observed for several sleep categories. Using 7-7.9 h sleep as reference, the adjusted injury risk (odds ratio [OR] for a worker sleeping a total of <5 h/day was 2.65 (95% confidence interval [CI]: 1.57-4.47), for 5-5.9 h 1.79 (95% CI: 1.22-2.62), and for 6-6.9 h 1.40 (95% CI: 1.10-1.79). No other usual sleep duration categories were significantly different than the reference; however, for >10 h of usual daily sleep, the OR was marginally significantly elevated, 1.82 (95% CI: 0.96-3.47). These results suggest significant increases in work-related injury risk with decreasing usual daily self-reported sleep hours and increasing weekly work hours, independent of industry, occupation, type of pay, sex, age, education, and body mass.

Comparative levels of excessive daytime sleepiness in common medical disorders

INTRODUCTION

Sleep restriction and sleep disorders are common causes of excessive daytime sleepiness (EDS). Medical disorders (MD) can also cause EDS, but previous studies have used non-standardized measures, selected samples, or have examined EDS in singular disorders. This study describes the relative degree of EDS associated with medical disorders to provide comparative data across a range of common medical conditions in a large unselected community-based sample.

METHODS

Responses of 2612 individuals (aged 18-65) were assessed after excluding those with suspected sleep disordered breathing, narcolepsy, and shift workers. Participants across a range of medical disorders were evaluated using the Epworth Sleepiness Scale (ESS) and patient reports of nocturnal sleep.

RESULTS

Sixty-seven percent of the sample reported a MD. The prevalence of EDS (ESS>or=10) was 31.4% in individuals with MD and increased as a function of a number of MD (0 MD=29.4%, 1 MD=28.4%, 2 MD=31.0%, 3 MD=35.3%, 4 MD=38.4%). Disorders which were independent predictors of EDS were ulcers OR=2.21 (95% CI=1.35-3.61), migraines OR=1.36 (95% CI=1.08-1.72), and depression OR=1.46 (95% CI=1.16-1.83) after controlling for other conditions, age, gender, time in bed, caffeine, smoking and alcohol use. Participants with ulcers had the highest prevalence of sleepiness, 50.0%, as well as the highest level of problems falling asleep (40.8%) and awakenings during the night (62.5%).

CONCLUSIONS

Individuals with ulcers, migraines, and depression have independent and clinically significant levels of EDS relative to other common MD.

An improved algorithm for automatic detection of saccades in eye movement data and for calculating saccade parameters

This analysis of time series of eye movements is a saccade-detection algorithm that is based on an earlier algorithm. It achieves substantial improvements by using an adaptive-threshold model instead of fixed thresholds and using the eye-movement acceleration signal. This has four advantages: (1) Adaptive thresholds are calculated automatically from the preceding acceleration data for detecting the beginning of a saccade, and thresholds are modified during the saccade. (2) The monotonicity of the position signal during the saccade, together with the acceleration with respect to the thresholds, is used to reliably determine the end of the saccade. (3) This allows differentiation between saccades following the main-sequence and non-main-sequence saccades. (4) Artifacts of various kinds can be detected and eliminated. The algorithm is demonstrated by applying it to human eye movement data (obtained by EOG) recorded during driving a car. A second demonstration of the algorithm detects microsleep episodes in eye movement data.

Sleepiness and prediction of driver impairment in simulator studies using a Cox proportional hazard approach

Cox proportional hazard models were used to study relationships between the event that a driver is leaving the lane caused by sleepiness and different indicators of sleepiness. In order to elucidate different indicators' performance, five different models developed by Cox proportional hazard on a data set from a simulator study were used. The models consisted of physiological indicators and indicators from driving data both as stand alone and in combination. The different models were compared on two different data sets by means of sensitivity and specificity and the models' ability to predict lane departure was studied. In conclusion, a combination of blink indicators based on the ratio between blink amplitude and peak closing velocity of eyelid (A/PCV) (or blink amplitude and peak opening velocity of eyelid (A/POV)), standard deviation of lateral position and standard deviation of lateral acceleration relative road (ddy) was the most sensitive approach with sensitivity 0.80. This is also supported by the fact that driving data only shows the impairment of driving performance while blink data have a closer relation to sleepiness. Thus, an effective sleepiness warning system may be based on a combination of lane variability measures and variables related to eye movements (particularly slow eye closure) in order to have both high sensitivity (many correct warnings) and acceptable specificity (few false alarms).

Fatores determinantes da atividade dos motoristas de caminhão e repercussões à saúde: um olhar a partir da análise coletiva do trabalho

Este estudo tem o intuito de caracterizar a atividade do motorista de caminhão quanto à demanda do trabalho e aos desafios impostos pela sua organização do trabalho. Foi utilizado o método da Análise Coletiva do Trabalho, que descreve a atividade a partir dos depoimentos dos trabalhadores durante reuniões com pesquisadores, com foco nos fatores que poderiam atuar como determinantes de acidentes e doenças relacionadas ao trabalho. Um total de 100 motoristas de duas empresas, submetidos a jornadas distintas de trabalho, participaram das reuniões. Os resultados revelaram que a falta de autonomia é uma das maiores queixas dos motoristas que trabalham no perímetro urbano durante o dia. Já o motorista que trabalha em horários irregulares e faz longas viagens trabalha sob tensão para cumprir os horários de entrega das mercadorias. O consumo de estimulantes constitui uma prática comum entre os motoristas decorrente das condições de trabalho, em especial a dificuldade de cumprir os horários e as longas jornadas, sendo parcialmente reconhecida por eles como um risco à saúde. Acrescem-se problemas relacionados à falta de segurança que atingem tanto os que atuam no perímetro urbano, como os que trabalham nas estradas. A análise da atividade destes motoristas revela uma realidade que merece intervenções voltadas para a melhoria de suas condições de trabalho, em especial no que se refere à regulamentação da jornada e à fiscalização de seu cumprimento, além de ações de promoção da saúde.

Factors correlated with traffic accidents as a basis for evaluating Advanced Driver Assistance Systems

This study aims to identify factors which influence and cause errors in traffic accidents and to use these as a basis for information to guide the application and design of driver assistance systems. A total of 474 accidents were examined in depth for this study by means of a psychological survey, data from accident reports, and technical reconstruction information. An error analysis was subsequently carried out, taking into account the driver, environment, and vehicle sub-systems. Results showed that all accidents were influenced by errors as a consequence of distraction and reduced activity. For crossroad accidents, there were further errors resulting from sight obstruction, masked stimuli, focus errors, and law infringements. Lane departure crashes were additionally caused by errors as a result of masked stimuli, law infringements, expectation errors as well as objective and action slips, while same direction accidents occurred additionally because of focus errors, expectation errors, and objective and action slips. Most accidents were influenced by multiple factors. There is a safety potential for Advanced Driver Assistance Systems (ADAS), which support the driver in information assimilation and help to avoid distraction and reduced activity. The design of the ADAS is dependent on the specific influencing factors of the accident type.

Wakefulness in young and elderly subjects driving at night in a car simulator

Young drivers are over-represented in nighttime traffic accidents and several studies have suggested that many accidents are associated with elevated sleepiness levels. It has been suggested that there may be a connection between lowered wake capacity and functional sensory motor skills on the one hand and sleep deprivation at the circadian low in young drivers on the other. Performance during a 45/min evening and night drive among young (n=10, age range 18-24 years) and elderly (n=10, age range 55-64 years) subjects was studied using a moving base driving simulator. EEG was measured continuously. Every 5 min, subjects were rated on the Karolinska Sleepiness Scale (KSS). Saliva cortisol was assessed before and after each drive. The results showed that sleepiness increased across each drive and was higher among young drivers at night. Relative EEG power increased among older drivers for frequencies of 10-16Hz. The sigma 1 frequency band (12-14Hz) proved particularly sensitive to sustained driving, and was elevated among subjects in the elderly group. Cortisol levels before and after the evening and night drive showed higher mean levels for elderly subjects. The present study has demonstrated that young drivers were more sleepy while driving at night. The effects could represent a mobilization of effort and a reorganization of brain firing pattern among older subjects, possibly reflecting better ability and effort to resist sleepiness.

Hazard perception in novice and experienced drivers: the effects of sleepiness

One driver skill that has been found to correlate with crash risk is hazard perception ability. The purpose of this study was to investigate how hazard perception latencies change between high and low sleepiness for a high risk group (novice drivers) and a lower risk group (experienced drivers). Thirty-two novice drivers (aged 17-24 years) and 30 experienced drivers (aged 28-36) completed a validated video-based hazard perception test, in which participants were asked to anticipate genuine traffic conflicts in footage filmed from the driver's perspective, with separate groups tested at either 10a.m. (lower sleepiness) or at 3a.m. (higher sleepiness). We found a significant interaction between sleepiness and experience, indicating that the hazard perception skills of the more experienced drivers were relatively unaffected by mild increases in sleepiness while the inexperienced drivers were significantly slowed. The findings suggest that the disproportionate sleepiness-related accident involvement of young, inexperienced drivers could be partly due to a slowing of their ability to anticipate traffic hazards.

Ocular parameters as an objective tool for the assessment of truck drivers fatigue

Ocular parameters are influenced by sleep derivation and the use of chemical substances which are two major causes for traffic accidents. We assessed the use of these parameters as an objective screening tool for a driver's fitness for duty. Pupillary diameter, pupil reaction to light and saccadic velocity were measured in 29 army truck drivers every morning for two months and compared to baseline measurements taken while the subjects were alert. An index which expressed the difference between study and baseline measurements was calculated, and drivers with significant deviation from baseline were disqualified and interviewed. Non-disqualified drivers served as controls. Twenty-nine percent of disqualified drivers reported sleeping less than the minimum of 7h required by army regulations compared with 8% of control drivers (p=0.01). Disqualified drivers had worse sleep quality the night before the test (Groningen Sleep Quality Scale, p=0.03) and incurred more accidents per driving day during their service (0.023 vs. 0.015 accidents/day, p=0.03). Two disqualified drivers admitted to using alcohol or sleeping pills. Thus, these ocular parameters may serve as a screening tool for drivers that are at high risk for driving. Drivers who were disqualified even once, tend to be involved in more motor vehicle accidents than their peers.

Road casualties and changes in risky driving behavior in France between 2001 and 2004 among participants in the GAZEL cohort

OBJECTIVES

We investigated behavioral changes in a large cohort of drivers to identify underlying causes of the decline in road casualties in France.

METHODS

In 2001 and 2004, 11,240 participants used self-administered questionnaires to report attitudes toward road safety and driving behaviors. Injury road traffic collisions were recorded from 2001 to 2005 through the cohort's annual questionnaire.

RESULTS

Between 2001 and 2004, speeding and cell phone use decreased concomitantly with a decrease in injury road traffic collision rates among participants. Reported driving while sleepy remained unchanged and driving while alcohol intoxicated was reported by a higher proportion in 2004 than in 2001. Decreases in speeding between 2001 and 2004 were strongly linked with positive attitudes toward road safety in 2001.

CONCLUSIONS

In this cohort, speeding and using a cell phone while driving decreased over the 2001 to 2004 period concomitantly with increases in traffic law enforcement and a dramatic decline in road mortality in France. However, the deterrent effect of traffic enforcement policies may have been reduced by negative attitudes toward traffic safety and having had a history of traffic penalty cancellations.