Long distance driving and self-induced sleep deprivation among automobile drivers

Dashcam video footage-based analysis of microsleep-related behaviors in truck collisions attributed to falling asleep at the wheel

OBJECTIVE

With the rapid spread of dashcams, many car accidents have been recorded; however, behavioral approaches using these dashcam video footage have not been sufficiently examined. We employed dashcam video footage to evaluate microsleep-related behaviors immediately prior to real-world truck collisions in professional drivers to explore a new solution to reduce collisions attributed to falling asleep at the wheel.

METHODS

In total, 3,120 s of video footage (60 s/case × 52 cases) from real-world truck collisions of 52 professional drivers obtained from interior and exterior dashcams were used and visually analyzed in a second-by-second manner to simultaneously evaluate any eye changes and microsleep-related behaviors (the driver's anti-sleepiness behavior, behavioral signs of microsleep, and abnormal vehicle behavior) during driving.

RESULTS

Assessment of the frequency of occurrence of each item of microsleep-related behavior in the 52 collisions revealed that the item "touching" in terms of anti-sleepiness behavior, "absence of body movement" in terms of behavioral signs of microsleep, and "inappropriate line crossing" in terms of abnormal vehicle behavior were observed at the highest rate in all drivers (46.2%, 75.0%, and 78.8%, respectively). Decreases in anti-sleepiness behavior coincided with increases in behavioral signs of microsleep and abnormal vehicle behavior, with collisions occurring within approximately 40 s of these changes. Collisions were more common among young people and in the early morning and evening.

CONCLUSION

Our dashcam video footage-based analysis in truck collisions attributed to falling asleep at the wheel revealed the process of changes in microsleep-related driver and vehicle behaviors, classified as anti-sleepiness behavior, behavioral signs of microsleep, and abnormal vehicle behavior. Based on these findings, to prevent collisions caused by falling asleep at the wheel, it is crucial to monitor not only the driver's eyes, but also the driver's whole body and vehicle behavior simultaneously to reliably detect microsleep-related behaviors.

Obstructive sleep apnea and excessive daytime sleepiness among commercial motor vehicle drivers in Lusaka, Zambia

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is a risk factor for a major public health problem, car crashes, due to excessive daytime sleepiness (EDS). Commercial vehicle driving (CVD) is a hazardous occupation, having a high fatality rate worldwide. There have been no studies on EDS and OSA in Zambia despite the high rate of annual road traffic accidents (RTAs). We aim to determine the prevalence of EDS and OSA risk among CVDs in Lusaka, Zambia, to assess the impact of OSA on high RTA rates.

METHODS

This was a cross-sectional study. The STOP BANG questionnaire and the Epworth Sleepiness Scale were used. Consecutive sampling of drivers was done who were divided into low and high risk of OSA (HROSA). The risk factors associated with OSA in the bivariate analyses were subjected to a multivariate logistic regression model.

RESULTS

One hundred thirty-six drivers participated in the study (all male) with a mean age of 48 ± 5 years. The prevalence of HROSA was 22.8% out of whom 67.7% also had a EDS. Only 9.6% of the total cohort had EDS without HROSA. Using Fisher's exact test, HROSA was significantly associated with older age (> 50 years, P < .001), obesity (body mass index >30, P < .001), neck circumference of > 40 cm (P = .032), and hypertension (P < .001). Snoring and EDS were significantly associated with RTAs (P < .0001 and P = .007, respectively).

CONCLUSIONS

High risk of OSA and EDS are common among CMV drivers in Zambia and underdiagnosed. The risk factors for OSA are amenable to preventive interventions.

CITATION

Simpamba K, May JL, Waghat A, Attarian H, Mateyo K. Obstructive sleep apnea and excessive daytime sleepiness among commercial motor vehicle drivers in Lusaka, Zambia. J Clin Sleep Med. 2023;19(7):1191-1198.

Influence of car seat firmness on seat pressure profiles and perceived discomfort during prolonged simulated driving

During a driving task, the seat-driver interface is particularly influenced by the external environment and seat features. This study compares the effect of two different seats (S₁ - soft & S₂ - firm) and the effect of visual simulation of different road types (city, highway, mountain, country), on pressure distribution and perceived discomfort during prolonged driving. Twenty participants drove two 3-h sessions (one per seat) on a static simulator. Contact Pressure (CP), Contact Surface (CS), and Seat Pressure Distribution Percentage (SPD%) were analyzed throughout, using two pressure mats positioned on seat cushion and backrest. Whole-body and local discomfort for each body part were rated every 20 min. The softer seat, S₁, induced a greater contact surface on cushion and backrest and a lower SPD%, reflecting better pressure distribution. Pressure profiles were asymmetrical for both S₁ and S_2, with higher CP under left buttock (LBu) and right lower back (RLb) and greater CS under thighs and RLb. Pressure distribution was less homogeneous on mountain and city roads than on monotonous roads (highway and country). Despite the pressure differences between the seats, however, both led to similar increases in perceived whole-body discomfort throughout the driving session. Moreover, the highest discomfort scores were in the neck and the lower back areas, whatever the seat. These findings on pressure variables may have implications for the design of backrests and cushions to ensure more homogeneous pressure distribution, even though this is not shown to minimize perceived driver discomfort.

Car seat impact on driver's sitting behavior and perceived discomfort during prolonged real driving on varied road types

Prolonged driving under real conditions can entail discomfort linked to driving posture, seat design features, and road properties like whole-body vibrations (WBV). This study evaluated the effect of three different seats (S1 = soft; S2 = firm; S3 = soft with suspension system) on driver's sitting behavior and perceived discomfort on different road types in real driving conditions. Twenty-one participants drove the same 195 km itinerary alternating highway, city, country, and mountain segments. Throughout the driving sessions, Contact Pressure (CP), Contact Surface (CS), Seat Pressure Distribution Percentage (SPD%) and Repositioning Movements (RM) were recorded via two pressure mats installed on seat cushion and backrest. Moreover every 20 minutes, participants rated their whole-body and local discomfort. While the same increase in whole-body discomfort with driving time was observed for all three seats, S3 limited local perceived discomfort, especially in buttocks, thighs, neck, and upper back. The pressure profiles of the three seats were similar for CP, CS and RM on the backrest but differed on the seat cushion. The soft seats (S1 & S3) showed better pressure distribution, with lower SPD% than the firm seat (S2). All three showed highest CP and CS under the thighs. Road type also affected both CP and CS of all three seats, with significant differences appearing between early city, highway and country segments. In the light of these results, automotive manufacturers could enhance seat design for reduced driver discomfort by combining a soft seat cushion to reduce pressure peaks, a firm backrest to support the trunk, and a suspension system to minimize vibrations.

Do hypnotics increase the risk of driving accidents or near miss accidents due to hypovigilance? The effects of sex, chronic sleepiness, sleep habits and sleep pathology

Driving accidents due to hypovigilance are common but the role of hypnotics is unclear in patients suffering from sleep disorders. Our study examined factors influencing accidents and near miss accidents attributed to sleepiness at the wheel (ANMAS). Using data from an online questionnaire aimed at patients with sleep disorders, we analysed the associations between ANMAS, sociodemographic data, symptoms of sleep disorders, severity of insomnia (Insomnia Severity Index (ISI)) symptoms of anxiety and depression (Hospital Anxiety and Depression scale with depression (HADD) and anxiety (HADA) subscales), chronic sleepiness (Epworth sleepiness scale ESS), hypnotic use and information about sleep habits. Hypnotics were hierarchically grouped into Z-drugs, sedative medication, melatonin and over the counter (OTC) alternative treatments. Of 10802 participants; 9.1% reported ANMAS (Men 11.1% women 8.3%) and 24.4% took hypnotics (Z-drugs 8.5%, sedative medication 8%, melatonin 5.6% and alternative treatments 2.5%). Logistic regression analysis identified the following risk factors for ANMAS: moderate (OR 2.4; CI: 2.10-2.79) and severe sleepiness (ESS OR 5.66; CI: 4.74-6.77), depression (HADD OR 1.2; CI: 1.03-1.47), anxiety (HADA OR 1.2;CI: 1.01-1.47), and insufficient sleep (OR1.4; CI: 1.2-1.7). Hypnotics were not associated with an increased risk of ANMAS in patients suffering from insomnia. Risk factors varied according to sex: in females, sex (OR 0.; CI: 0.55-0.74), mild insomnia (OR 0.5; CI: 0.3-0.8) and use of alternative treatments (OR 0.455, CI:0.23-0.89) were protective factors and risk was increased by sleepiness, sleep debt, social jetlag, caffeine use, anxiety and depression. In men no protective factors were identified: sleepiness, sleep debt, and severe insomnia were associated with an increased risk of ANMAS. In clinical practice, all patients with daytime sleepiness and men with severe insomnia should be counselled concerning driving risk and encouraged to avoid sleep debt.

Sleep Restriction, Sleep Hygiene, and Driving Safety: The Importance of Situational Sleepiness

Sleep-related accidents are a frequent cause of death and injury in the world. Poor sleep hygiene is responsible for sleep deprivation, which is clearly associated with an increased risk of accidents. Evidence shows that self-reported sleepiness at the wheel and reporting of inappropriate line-crossings are strong predictors of accident risk. Although the Epworth sleepiness scale is widely used in clinical practice, it is not the best to evaluate driving risks. Simple questions on the occurrence of near misses and sleepiness at the wheel should be asked systematically to address the issue of fitness to drive.

Excessive daytime sleepiness in obstructive sleep apnea: implications for driving licenses

PURPOSE

Excessive daytime sleepiness (EDS) while driving is a major international public health issue resulting in a more than doubled risk of motor vehicle accidents (MVAs). Obstructive sleep apnea (OSA) is the most frequent medical cause of EDS. Therefore, the European Union Directive 2014/85/EU determined that "untreated moderate to severe OSA coincident with EDS constitutes a medical disorder leading to unfitness to drive." The paper aims are to provide a brief review of sleepiness and its implications for driving safety, as well as to describe the subjective and objective methods to accurately evaluate EDS in order to assess fitness to drive in patients with OSA.

METHODS

We examined databases including PubMed, Medline, and EMBASE using the search terms "sleepiness at the wheel, excessive daytime sleepiness, sleepiness measure, sleep-wake cycle, obstructive sleep apnea, driving license, fitness to drive."

RESULTS

Significant interindividual variability in EDS exists in patients with comparable severity of OSA. Objective methods of measuring EDS are too expensive and time consuming to be suitable for the certification of driving licenses. The reliability of subjective methods depends upon the clinical setting and subjective tools assess only limited aspects of EDS. Objective measures, such as biochemical biomarkers, must, therefore, support subjective methods.

CONCLUSIONS

Extensive data have supported different subjective and objective methods for the appraisal of EDS in patients with OSA depending upon the clinical and experimental setting. Challenges remain to determine an appropriate tool for the evaluation of fitness to drive.

Detection and prediction of driver drowsiness using artificial neural network models

Not just detecting but also predicting impairment of a car driver's operational state is a challenge. This study aims to determine whether the standard sources of information used to detect drowsiness can also be used to predict when a given drowsiness level will be reached. Moreover, we explore whether adding data such as driving time and participant information improves the accuracy of detection and prediction of drowsiness. Twenty-one participants drove a car simulator for 110min under conditions optimized to induce drowsiness. We measured physiological and behavioral indicators such as heart rate and variability, respiration rate, head and eyelid movements (blink duration, frequency and PERCLOS) and recorded driving behavior such as time-to-lane-crossing, speed, steering wheel angle, position on the lane. Different combinations of this information were tested against the real state of the driver, namely the ground truth, as defined from video recordings via the Trained Observer Rating. Two models using artificial neural networks were developed, one to detect the degree of drowsiness every minute, and the other to predict every minute the time required to reach a particular drowsiness level (moderately drowsy). The best performance in both detection and prediction is obtained with behavioral indicators and additional information. The model can detect the drowsiness level with a mean square error of 0.22 and can predict when a given drowsiness level will be reached with a mean square error of 4.18min. This study shows that, on a controlled and very monotonous environment conducive to drowsiness in a driving simulator, the dynamics of driver impairment can be predicted.

Insufficient sleep reduces voting and other prosocial behaviours

Insufficient sleep is a growing public health concern in industrial societies. Although a lack of sleep is known to negatively affect private behaviours-such as working or going to school-comparatively little is known about its consequences for the social behaviours that hold society and democracy together. Using three complementary methods, we show how insufficient sleep affects various measures of civic participation. With survey data from two countries, we show that insufficient sleep predicts lower voter turnout. Next, with a geographical regression discontinuity design, we demonstrate that individuals from the United States who tend to sleep less due to circadian impacts of time-zone boundaries are also less likely to vote. Finally, we experimentally manipulate short-term sleep over a two-stage study. We observe that the treatment decreases the levels of civic engagement, as shown by their willingness to vote, sign petitions and donate to charities. These results highlight the strong negative consequences that current levels of insufficient sleep have on vitally important measures of social capital.

Commuting and Sleep: Results From the Hispanic Community Health Study/Study of Latinos Sueño Ancillary Study

INTRODUCTION

Commute time is associated with reduced sleep time, but previous studies have relied on self-reported sleep assessment. The present study investigated the relationships between commute time for employment and objective sleep patterns among non-shift working U.S. Hispanic/Latino adults.

METHODS

From 2010 to 2013, Hispanic/Latino employed, non-shift-working adults (n=760, aged 18-64 years) from the Sueño study, ancillary to the Hispanic Community Health Study/Study of Latinos, reported their total daily commute time to and from work, completed questionnaires on sleep and other health behaviors, and wore wrist actigraphs to record sleep duration, continuity, and variability for 1 week. Survey linear regression models of the actigraphic and self-reported sleep measures regressed on categorized commute time (short: 1-44 minutes; moderate: 45-89 minutes; long: ≥90 minutes) were built adjusting for relevant covariates. For associations that suggested a linear relationship, continuous commute time was modeled as the exposure. Moderation effects by age, sex, income, and depressive symptoms also were explored.

RESULTS

Commute time was linearly related to sleep duration on work days such that each additional hour of commute time conferred 15 minutes of sleep loss (p=0.01). Compared with short commutes, individuals with moderate commutes had greater sleep duration variability (p=0.04) and lower interdaily stability (p=0.046, a measure of sleep/wake schedule regularity). No significant associations were detected for self-reported sleep measures.

CONCLUSIONS

Commute time is significantly associated with actigraphy-measured sleep duration and regularity among Hispanic/Latino adults. Interventions to shorten commute times should be evaluated to help improve sleep habits in this minority population.

Sleepiness while driving and shiftwork patterns among Korean bus drivers

BACKGROUND

Sleepiness while driving has been regarded as a major cause of death due to traffic accidents. We compared the degree of sleepiness across five different working time periods (first, morning, post-lunch, afternoon, and last) among Korean bus drivers with different shift types (Daily two shift/Alternating day shift).

METHOD

We interviewed 332 bus drivers with two shift types (Daily two shift, 128; Alternating day shift, 204). The questionnaire included demographic information (age, alcohol consumption and history of disease), a sleep disorder diagnosed by a doctor, job duration, the number of workdays in the past month, average working hours per workday and week, sleepiness while driving (Karolinska Sleepiness Scale), and sleeping time for both workdays and off-days. We conducted log-binomial regression analyses and produced prevalence ratios (PRs) of severe sleepiness (KSS ≥ 7) while driving with 95% confidence intervals (95% CI) to identify the difference in sleepiness for five working times between both groups.

RESULTS

For the first and morning periods, there were no statistically significant differences in the KSS scores between the two groups. However, from lunch to last driving, drivers with Alternating day shift had a much larger proportion of severe sleepiness than those on Daily two shift. Thirteen (10.2%), 2 (1.6%) and 7 (5.5%) Daily two shift workers reported severe sleepiness in the post-lunch, afternoon and last periods. In contrast, 81 (39.7%), 63 (30.9%) and 64 (31.4%) of Alternating day shift drivers experienced severe sleepiness during the post-lunch, afternoon and last driving periods (p < 0.0001). According to the log-binomial regression analyses, Alternating day shift was associated with severe sleepiness from lunch to last driving. After adjusting for job duration, alcohol consumption and sleeping time on workdays, the PRs were 3.97 (95% CI: 2.29-6.90) post-lunch, 18.26 (95% CI: 4.51-73.89) in the afternoon and 5.71 (95% CI: 2.51-12.99) for the last driving period.

CONCLUSION

We found that Alternating day shift bus drivers suffered from more sleepiness while driving from lunch to last driving than Daily two shift bus drivers. This difference may be because Alternating day shift drivers had more irregular work schedules and longer working hours per day and week.

Association between reported sleep need and sleepiness at the wheel: comparative study on French highways between 1996 and 2011

OBJECTIVE

To investigate the evolution over 15 years of sleep schedules, sleepiness at the wheel and driving risk among highway drivers.

METHODS

Comparative survey including questions on usual sleep schedules and before the trip, sleepiness at the wheel, the Epworth sleepiness scale, Basic Nordic Sleep Questionnaire (BNSQ) and a travel questionnaire.

RESULTS

80% of drivers stopped by the highway patrol agreed to participate in both studies with a total of 3545 drivers in 2011 and 2196 drivers in 1996 interviewed. After standardisation based on sex, age and mean annual driving distance, drivers in 2011 reported shorter sleep time on week days (p<0.0001), and week-ends (p<0.0001) and shorter optimal sleep time (p<0.0001) compared to 1996 drivers. There were more drivers sleepy at the wheel in 2011 than in 1996 (p<0.0001) and 2.5 times more drivers in 2011 than in 1996 had an Epworth sleepiness score >15 indicating severe sleepiness.

CONCLUSIONS

Even if drivers in 2011 reported good sleep hygiene prior to a highway journey, drivers have reduced their mean weekly sleep duration over 15 years and have a higher risk of sleepiness at the wheel. Sleep hygiene for automobile drivers remains an important concept to address.

The on-road experiences and awareness of sleepiness in a sample of Australian highway drivers: A roadside driver sleepiness study

OBJECTIVE

Driver sleepiness contributes substantially to road crash incidents. Simulator and on-road studies clearly reveal an impairing effect from sleepiness on driving ability. However, the degree to which drivers appreciate the dangerousness of driving while sleepy is somewhat unclear. This study sought to determine drivers' on-road experiences of sleepiness, their prior sleep habits, and personal awareness of the signs of sleepiness.

METHODS

Participants were a random selection of 92 drivers traveling on a major highway in the state of Queensland, Australia, who were stopped by police as part of routine drink driving operations. Participants completed a brief questionnaire that included demographic information, sleepy driving experiences (signs of sleepiness and on-road experiences of sleepiness), and prior sleep habits. A modified version of the Karolinska Sleepiness Scale (KSS) was used to assess subjective sleepiness in the 15 min prior to being stopped by police.

RESULTS

Participants' ratings of subjective sleepiness were quite low, with 90% reporting being alert to extremely alert on the KSS. Participants were reasonably aware of the signs of sleepiness, with many signs of sleepiness associated with on-road experiences of sleepiness. Additionally, the number of hours spent driving was positively correlated with the drivers' level of sleep debt.

CONCLUSIONS

The results suggest that participants had moderate experiences of driving while sleepy and many were aware of the signs of sleepiness. The relationship between driving long distances and increased sleep debt is a concern for road safety. Increased education regarding the dangers of sleepy driving seems warranted.

Using naturalistic driving data to explore the association between traffic safety-related events and crash risk at driver level

There has been considerable research conducted over the last 40 years using traffic safety-related events to support road safety analyses. Dating back to traffic conflict studies from the 1960s these observational studies of driver behavior have been criticized due to: poor quality data; lack of available and useful exposure measures linked to the observations; the incomparability of self-reported safety-related events; and, the difficulty in assessing culpability for safety-related events. This study seeks to explore the relationships between driver characteristics and traffic safety-related events, and between traffic safety-related events and crash involvement while mitigating some of those limitations. The Virginia Tech Transportation Institute 100-Car Naturalistic Driving Study dataset, in which the participants' vehicles were instrumented with various cameras and sensors during the study period, was used for this study. The study data set includes 90 drivers observed for 12-13 months driving. This study focuses on single vehicle run-off-road safety-related events only, including 14 crashes and 182 safety-related events (30 near crashes, and 152 crash-relevant incidents). Among the findings are: (1) drivers under age 25 are significantly more likely to be involved in safety-related events and crashes; and (2) significantly positive correlations exist between crashes, near crashes, and crash-relevant incidents. Although there is still much to learn about the factors affecting the positive correlation between safety-related events and crashes, a Bayesian multivariate Poisson log-normal model is shown to be useful to quantify the associations between safety-related events and crash risk while controlling for driver characteristics.

[Excessive daytime sleepiness. An epidemiological study based on a "sleep/breathing" questionnaire]

BACKGROUND

A field survey used a "sleep-breathing" questionnaire to estimate the prevalence of the excessive daytime sleepiness in a sample of middle-aged males.

METHODS

Eight hundred and fifty men aged 22 to 66 years agreed to answer a questionnaire and have anthropometric measurements. To the question on excessive daytime sleepiness, 90 subjects (10.8%) responded "often" or "almost always"; 740 gave a negative answer.

RESULTS

The sleepy subjects were older and had a higher "central" weight. All the sleep-disturbed breathing symptoms and those suggesting sleep disturbances were more frequent in sleepy subjects. Sleepiness was significantly associated with sleep apnea and chronic bronchitis. Logistic regression identified six items independently associated with daytime sleepiness; there were three indirect indicators of sleepiness, age, a history of chronic bronchitis and disruptive movements during sleep.

CONCLUSIONS

This epidemiologic study in a sample of active middle-aged males confirms the association of daytime sleepiness with a series of respiratory and non-respiratory sleep disturbances. The original findings are the role of a "central" obesity, the association with nightmares, and the role of chronic bronchitis as a determinant of daytime sleepiness.

The distribution of sleepiness, sleep and work hours during a long distance morning trip: a comparison between night- and non-night workers

Few studies have examined the extent of driver sleepiness during a long distance morning trip. Sleepiness at this time may be high because of night work, waking early to commence work or travel, sleep disorders and the monotony of driving long distances. The objective of this study was to estimate the prevalence of chronic sleepiness (Epworth sleepiness score ≥10) and sleep restriction (≤5h) in a sample of 649 drivers. Participants driving between 08:00 and 10:00 on three highways in regional Australia participated in a telephone interview. Approximately 18% of drivers reported chronic sleepiness. The proportions of night workers (NW) and non-night workers (NNW) with chronic sleepiness were not significantly different but males reported a significantly greater proportion of chronic sleepiness than females. The NW group had a significantly greater proportion of drivers with ≤5h of sleep in the previous 24 and 48h, fewer nights of full sleep (≤4), acute sleepiness and longer weekly work hours. The NW group reported driving a significantly longer distance at Time 1 (Mean=140.29±72.17km, versus 117.55±89.74km) and an additional longer distance to complete the journey (Mean=89.33±95.23km, versus 64.77±94.07km). The high proportions of sleep restriction and acute sleepiness among the NW group, and the amount of chronic sleepiness in the NW and NNW groups reported during a long distance morning trip may be of concern for driver safety.

Sleepiness, long distance commuting and night work as predictors of driving performance

Few studies have examined the effect of working night shift and long distance commuting. We examined the association between several sleep related and demographic variables, commuting distance, night work and use of mobile phones on driving performance. We used a prospective design to recruit participants and conducted a telephone survey (n = 649). The survey collected demographic and journey details, work and sleep history and driving performance concerning the day the participant was recruited. Participants also completed the Karolinska Sleepiness Scale and the Epworth Sleepiness Scale. Night workers reported significantly more sleepiness, shorter sleep duration and commuting longer distances. Seven variables were significant predictors of lane crossing. The strongest predictor was acute sleepiness (OR = 5.25, CI, 1.42–19.49, p<0.01) followed by driving ≥150 kms (OR = 3.61, CI, 1.66–7.81, p<0.001), obtaining less than 10 hours sleep in the previous 48 hours (OR = 2.58, CI, 1.03–6.46, p<0.05), driving after night shift (OR = 2.19, CI, 1.24–3.88, p<0.001), being <43 years old (OR = 1.95, CI, 1.11–3.41, p<0.05) and using mobile phones during the journey (OR = 1.90, CI, 1.10–3.27, p<0.05). Sleep related variables, long-distance commuting and night work have a major impact on lane crossing. Several interventions should be considered to reduce the level of sleepiness in night workers.

Reliability of simulator driving tool for evaluation of sleepiness, fatigue and driving performance

STUDY OBJECTIVE

To compare the impact of extended wakefulness (i.e., sleepiness) and prolonged driving (i.e., fatigue) at the wheel in simulated versus real-life driving conditions.

DESIGN

Participants drove on an INRETS-MSIS SIM2 simulator in a research laboratory or an open French highway during 3 nocturnal driving sessions. A dose-response design of duration of nocturnal driving was used: a 2 h short driving session (3-5 AM), a 4 h intermediate driving session (1-5 AM) and an 8 h long driving session (9 PM-5 AM).

PARTICIPANTS

Two groups of healthy male drivers (20 for simulated driving and 14 drivers for real driving; mean age±SD=22.3±1.6 years), free of sleep disorders.

MEASUREMENTS

Number of inappropriate line crossings, self-rated fatigue and sleepiness were recorded in the last hour of driving sessions to control the effects of prior waking time and time of day.

RESULTS

Compared to the daytime reference session, both simulated and real driving performance were affected by a short nocturnal driving session (P<.05 and P<.001, respectively). Extension of nocturnal driving duration affected simulated performance nonlinearly and more severely than that of real driving (P<.001). Compared to the daytime reference session, short nocturnal simulated and real driving sessions increased self-perceived fatigue and sleepiness. Real and simulated driving conditions had an identical impact on fatigue and sleepiness during extended periods of nocturnal driving.

CONCLUSIONS

In healthy subjects, the INRETS-MSIS SIM2 simulator appropriately measures driving impairment in terms of inappropriate line crossings related to extended wakefulness but has limitations to measure the impact of extended driving on drivers' performance.

Short sleep in young adults: Insomnia or sleep debt? Prevalence and clinical description of short sleep in a representative sample of 1004 young adults from France

BACKGROUND

Increasing evidence suggests an association between short sleep with adverse health outcomes: obesity, type 2 diabetes and hypertension. But there are few or no data on "who these short sleepers are" in the general population.

OBJECTIVES

To describe short sleepers and the associated sleep disorders in young adults.

METHODS

Cross-sectional telephone survey in a representative sample of 1004 French young adults (25-45 years old). Total sleep time (TST), insomnia, snoring, sleepiness and daytime consequences were assessed using subjective validated tools. Short sleepers were defined as sleeping <6h a weekday (sleep+nap+pauses). Sleep debt was defined as those who "sleep 90 min less than the sleep they need to be in good shape."

RESULTS

Prevalence of short sleep was 18%, insomnia 12%, and sleep debt 20% in the total group. Among short sleepers, 16% had insomnia, 45% sleep debt, and 39% neither. Short sleepers were significantly mostly males, blue collar workers and more overweight and obese compared to nonshort sleepers. Working >10h per day, smoking and drinking coffee after 5p.m. were also significantly associated with short sleep. Short sleepers had higher Epworth sleepiness scale ESS scores (7.8 vs 6.7; p = 0.0058) and more sleepiness while driving (11.5% vs 2.9%; p < 0.0001).

CONCLUSION

Short sleep is highly prevalent in young adults but is not an homogeneous group, including both insomniacs and subjects with or without sleep debt. Short sleep has to be defined more precisely in order to better understand its impact on public health.

Sleep loss and accidents--work hours, life style, and sleep pathology

A very important outcome of reduced sleep is accidents. The present chapter will attempt to bring together some of the present knowledge in this area. We will focus on the driving situation, for which the evidence of the link between sleep loss and accidents is quite well established, but we will also bring up working life in general where evidence is more sparse. It should be emphasized that reduced sleep as a cause of accidents implies that the mediating factor is sleepiness (or fatigue). This link is discussed elsewhere in this volume, but here we will bring in sleepiness (subjective or physiological) as an explanatory factor of accidents. Another central observation is that many real life accident studies do not link accidents to reduced sleep, but infer reduced sleep and/or sleepiness from the context, like, for example, from work schedules, life styles, or sleep pathology. Reduced sleep is mainly due to suboptimal work schedules (or to a suboptimal life style) or to sleep pathology. We have divided the present chapter into two areas.

Effectiveness of UK motorway services areas in reducing sleep-related and other collisions

In the UK, motorway service areas (MSAs) are believed to be helpful in reducing sleep ('fatigue') related collisions (SRCs), however, their actual effectiveness has yet to be evaluated. During a 2-3-year period, and over two sections of UK motorways comprising 14 MSA sites, assessments were undertaken of all fatal and injury road traffic collisions (RTCs), especially SRCs. Analyses examined whether there was: (i) a reduction in collisions 16 km beyond MSAs compared with the same distance beforehand; (ii) accumulation of collisions with increasing inter-MSA distances. Within the 16 km regions there was a non-significant fall in all RTCs from 355 before MSAs, to 304 afterwards. However, the 22% decrease in SRCs (108 vs. 84) was significant. Cars comprised the greatest reduction in SRCs possibly attributable to a MSA. Including and beyond these 16 km regions, there was no correlation between inter-MSA distances and accumulated RTCs or SRCs (n=682 of which 181 were SRCs [26%]). There were obvious differences between MSAs in all these respects. Of the 23 fatal RTCs, 17 were SRCs. Whilst SRCs had their greatest daily incidence between 02:00 h and 06:00 h, as expected, MSAs seemed to have their least beneficial effect on SRCs during this vulnerable period, which is a matter for concern.

Extended driving impairs nocturnal driving performances

Though fatigue and sleepiness at the wheel are well-known risk factors for traffic accidents, many drivers combine extended driving and sleep deprivation. Fatigue-related accidents occur mainly at night but there is no experimental data available to determine if the duration of prior driving affects driving performance at night. Participants drove in 3 nocturnal driving sessions (3-5 am, 1-5 am and 9 pm-5 am) on open highway. Fourteen young healthy men (mean age [+/-SD] = 23.4 [+/-1.7] years) participated Inappropriate line crossings (ILC) in the last hour of driving of each session, sleep variables, self-perceived fatigue and sleepiness were measured. Compared to the short (3-5 am) driving session, the incidence rate ratio of inappropriate line crossings increased by 2.6 (95% CI, 1.1 to 6.0; P<.05) for the intermediate (1-5 am) driving session and by 4.0 (CI, 1.7 to 9.4; P<.001) for the long (9 pm-5 am) driving session. Compared to the reference session (9-10 pm), the incidence rate ratio of inappropriate line crossings were 6.0 (95% CI, 2.3 to 15.5; P<.001), 15.4 (CI, 4.6 to 51.5; P<.001) and 24.3 (CI, 7.4 to 79.5; P<.001), respectively, for the three different durations of driving. Self-rated fatigue and sleepiness scores were both positively correlated to driving impairment in the intermediate and long duration sessions (P<.05) and increased significantly during the nocturnal driving sessions compared to the reference session (P<.01). At night, extended driving impairs driving performances and therefore should be limited.

Aging and nocturnal driving: better with coffee or a nap? A randomized study

STUDY OBJECTIVE

To test the effects of coffee and napping on nocturnal driving in young and middle-aged participants.

DESIGN

A cup of coffee (200 mg of caffeine), a placebo (decaffeinated coffee, 15 mg of caffeine), or a 30-minute nap were tested. Participants drove 125 highway miles between 18:00 and 19:30 and between 02:00 and 03:30 after coffee, placebo, or a nap.

SETTING

Sleep laboratory and open French highway.

PARTICIPANTS

Twelve young (range, 20-25 years) and 12 middle-aged participants (range, 40-50 years).

MEASUREMENTS

Inappropriate line crossings, self-perceived fatigue and sleepiness, and polysomnographic recordings were analyzed.

RESULTS

Compared to daytime, after placebo the number of inappropriate line crossings was significantly increased (2 versus 73 for young participants, P < 0.01 and 0 versus 76 for the middle-aged participants, P < 0.05). Both coffee and napping reduced the risk of inappropriate line crossings, compared with placebo, in young participants (respectively, by three-quarters, incidence rate ratios [IRR] = 0.26 95% confidence interval [CI], 0.09-0.74, P < 0.05 and by two thirds, IRR = 0.34 95% CI, 0.20-0.58, P < 0.001) and in middle-aged participants (respectively by nine tenths, IRR = 0.11 95% CI, 0.05-0.21, P < 0.001 and by one fifth, IRR = 0.77 95% CI, 0.63-0.95, P < 0.05). A significant interaction between age and condition (IRR = 2.27 95% CI, 1.28-4.16 P < 0.01) showed that napping led to fewer inappropriate line crossings in younger participants than in middle-aged participants. During napping, young participants slept more (P < 0.01) and had more delta sleep (P < 0.05) than middle-aged participants. Self-perceived sleepiness and fatigue did not differ in both age groups, but coffee improved sleepiness (P < 0.05), whereas napping did not.

CONCLUSIONS

Coffee significantly improves performance in young and middle-aged participants. Napping is more efficient in younger than in older participants. Countermeasures to sleepiness should be adapted according to the age of drivers.

Sleep disorders, sleepiness and traffic safety: a public health menace

Sleep disorders are not uncommon and have been widely reported throughout the world. They have a profound impact on industrialized 24-h societies. Consequences of these problems include impaired social and recreational activities, increased human errors, loss of productivity, and elevated risk of accidents. Conditions such as acute and chronic insomnia, sleep loss, excessive sleepiness, shift-work, jet lag, narcolepsy, and sleep apnea warrant public health attention, since residual sleepiness during the day may affect performance of daily activities such as driving a car. Benzodiazepine hypnotics and zopiclone promote sleep, both having residual effects the following day including sleepiness and reduced alertness. In contrast, the non-benzodiazepine hypnotics zolpidem and zaleplon have no significant next-day residual effects when taken as recommended. Research on the effects of wakefulness-promoting drugs on driving ability is limited. Countermeasures for excessive daytime sleepiness have a limited effect. There is a need for a social awareness program to educate the public about the potential consequences of various sleep disorders such as narcolepsy, sleep apnea, shift-work-related sleep loss, and excessive daytime sleepiness in order to reduce the number of sleep-related traffic accidents.

Troubles respiratoires pendant le sommeil et accidents du travail ou de la vie courante

Obstructive sleep apnoeas affect a significant proportion of the middle-aged population. They are due to the closure of upper airways during sleep and cause fragmented sleep, which leads to excessive daily drowsiness. Sleepiness due to apnoea is acknowledged by 10 to 30% of subjects in epidemiological surveys. It impairs vigilance, and therefore represents a risk factor for traffic, domestic and work-related accidents. In the case of domestic accidents, a study shows an increased number of accidents have been reported by subjects with apnoeas; a second study reports the reduction in the frequency of such accidents after receiving appropriate treatment. Subjects suffering from sleep apnoeas also have a higher frequency of accidents at work. Workers with persistent daily drowsiness were also found to have a higher rate of absenteeism as well.

Sleep habits, sleepiness and accidents among truck drivers

OBJECTIVE: To evaluate the quality of sleep, shift work, alcohol and psychostimulant drug use, and the prevalence of accidents among truck drivers. METHOD: Data were collected using a demographic questionnaire, the Epworth Sleepiness Scale (ESS) and the Pittsburgh sleep quality index (PSQI). Statistical analysis was conducted using the Student t, chi-square, Pearson and Fisher tests. RESULTS: 43.2% of the drivers drove over 16 h a day, and 2.9% worked shifts. Mean number of sleep hours/day was 5.97±1.47; 23.8% slept <5 hours; 50.9% made use of alcohol, 95.6% of caffeine, and 11.1% of amphetamines. Mean PSQI was 4.95±2.56; 35.4% had a PSQI >5; 23 subjects snored more than three times a week (11.1%). Mean ESS was 6.56±4.2; 21.7% had a score >10. In the preceding five years, 27 drivers (13.1%) were involved in accidents, 5 of which resulted in injuries and 3 in deaths. CONCLUSION: Results showed a high prevalence of sleep disorders, use of alcohol and psychostimulant drugs, and accidents.

Subjective and predicted sleepiness while driving in young adults

Sleepiness is a significant contributor to car crashes and sleepiness related crashes have higher mortality and morbidity than other crashes. Young adult drivers are at particular risk for sleepiness related car crashes. It has been suggested that this is because young adults are typically sleepier than older adults because of chronic sleep loss, and more often drive at times of increased risk of acute sleepiness. This prospective study aimed to determine the relationship between predicted and perceived sleepiness while driving in 47 young-adult drivers over a 4-week period. Sleepiness levels were predicted by a model incorporating known circadian and sleep factors influencing alertness, and compared to subjective ratings of sleepiness during 2518 driving episodes. Results suggested that young drivers frequently drive while at risk of crashing, at times of predicted sleepiness (>7% of episodes) and at times they felt themselves to be sleepy (>23% of episodes). A significant relationship was found between perceived and predicted estimates of sleepiness. However, the participants nonetheless drove at these times. The results of this study may help preventative programs to specifically target factors leading to increased sleepiness when driving (particularly time of day), and to focus interventions to stop young adults from driving when they feel sleepy.

Fatigue, sleep restriction and driving performance

We ran a randomized cross-over design study under sleep-deprived and non-sleep-deprived driving conditions to test the effects of sleep restriction on real driving performance. The study was performed in a sleep laboratory and on an open French highway. Twenty-two healthy male subjects (age = 21.5 +/- 2 years; distance driven per year = 12,225 +/- 4739 km (7641 +/- 2962 miles) [mean +/- S.D.]) drove 1000 km (625 miles) over 10 h during five 105 min sessions on an open highway. Self-rated fatigue and sleepiness before each session, number of inappropriate line crossings from video recordings and simple reaction time (RT) were measured. Total crossings increased after sleep restriction (535 crossings in the sleep-restricted condition versus 66 after non-restricted sleep (incidence rate ratio (IRR): 8.1; 95% confidence interval (95% CI): 3.2-20.5; p < 0.001)), from the first driving session. The interaction between the two factors (conditionxtime of day) was also significant (F(5, 105) = 3.229; p < 0.05). Increasing sleepiness score was associated with increasing crossings during the next driving session in the sleep-restricted (IRR: 1.9; 95% CI: 1.4-2.4) but not in the non-restricted condition (IRR: 1.0; 95% CI: 0.8-1.3). Increasing self-perceived fatigue was not associated with increasing crossings in either condition (IRR: 0.95; 95% CI: 0.93-0.98 and IRR: 1.0; 95% CI: 0.98-1.02). Rested subjects drove 1000 km with four shorts breaks with only a minor performance decrease. Sleep restriction induced important performance degradation even though time awake (8h) and session driving times (105 min) were relatively short. Major inter-individual differences were observed under sleep restriction. Performance degradation was associated with sleepiness and not fatigue. Sleepiness combined with fatigue significantly affected RT. Road safety campaigns should encourage drivers to avoid driving after sleep restriction, even on relatively short trips especially if they feel sleepy.

Recovery after prolonged sleep deprivation: residual effects of slow-release caffeine on recovery sleep, sleepiness and cognitive functions

A long work schedule often results in sleep deprivation, sleepiness, impaired performance and fatigue. We investigated the residual effects of slow-release caffeine (SRC) on sleep, sleepiness and cognitive performance during a 42-hour recovery period following a 64-hour continuous wakefulness period in 16 healthy males, according to a double-blind, randomised, placebo-controlled, crossover study. Three hundred milligrams of SRC or placebo was given twice a day at 21:00 and 9:00 during the first 48 h of wakefulness. Recovery sleep was analysed with electroencephalography (EEG) and wrist actigraphy, daytime sleepiness with continuous EEG, sleep latency tests and actigraphy and cognitive functions with computerized tests from the NATO AGARD STRES battery. Both drug groups exhibited almost the same sleep architecture with a rebound of slow-wave sleep during both recovery nights and of REM sleep during the second night. Wakefulness level and cognitive functions were similarly impaired in both groups on the first day of recovery and partially returned to baseline on the second. To conclude, SRC appears to have no unwanted side-effects on recovery sleep, wakefulness and cognitive performance after a long period of sleep deprivation and might therefore be a useful choice over other psychostimulants for a long work schedule.

Sleepiness of occupational drivers

Drowsiness and sleeping at the wheel are now identified as the reasons behind fatal crashes and highway accidents caused by occupational drivers. For many years, fatigue has been associated to risk of accidents but the causes of this symptom were unclear. Extensive or nocturnal driving was associated to accidents but few reports differentiated fatigue from sleepiness. In the early nineties, epidemiological data started investigating sleepiness and sleep deprivation as cause of accidents. Sleepiness at the wheel, sleep restriction and nocturnal driving have been incriminated in 20% of traffic accidents. Drugs affecting the central nervous system (i.e., narcotic analgesics, antihistamine drugs), nocturnal breathing disorders and narcolepsy have been also associated with an increasing risk of accidents. Treatments improving daytime vigilance (i.e., nasal Continuous Positive Airway Pressure) reduce significantly the risk of traffic accidents for a reasonable economical cost. Sleep disorders among occupational drivers need to be systematically investigated. Chronic daytime sleepiness is still under diagnosed and sleep disorders (i.e. obstructive sleep apnea syndrome) are not enough explored and treated in this exposed population of sedentary males. Drivers education and work schedules integrating notions of sleep hygiene as well as promotion of sleep medicine could significantly improve road safety.

The future of work hours--the European view

In Europe the way work hours are handled varies between different countries. However, there are some issues that dominate the discussion in Europe and seem representative for what is happening. One such is the reduction of working hours--which was attempted in several countries but which now seems to be backfiring--probably related to the competition from countries outside Europe. Another area is compressed work hours--the drive towards maximizing the hours per work day in order to increase the number of days off. The health effects are debated--some find clear positive effects. A third area is company oriented flexible work hours, permitting the employer to make moderate changes in work hours when needed. The health impacts have not been evaluated but the loss of individual influence at work is obvious. In some parts of Europe self-determined work hours have been tried with very positive effects. The EU work hour directive is intended to provide uniformity but permits a counterproductive "opting out", creating problems of imbalance.

Effect of fatigue on performance measured by a driving simulator in automobile drivers

OBJECTIVE

To identify risk factors of performance decrement in automobile drivers.

METHODS

114 drivers (age <30 years, n=57; age > or =30 years, n=57) who stopped at a rest stop area on a freeway were recruited for the study. They filled out a questionnaire on their journey, sleep/wake patterns and performed a 30-min test on a driving simulator. The test evaluates, by computerized analysis, the lateral deviation of a virtual car from an appropriate trajectory on a virtual road. A sex/age matched control group was recruited in the community. Control subjects were studied at the same time of day as the index case driver. Controls had normal sleep wake schedule, absence of long driving and performed the same driving test.

RESULTS

Drivers performed significantly worse than controls on the driving test. Age and duration of driving were the main factors associated with decreased performance.

CONCLUSION

Our driving simulator can identify fatigue generated by driving but results must be considered in relation with age of subjects.

Driving simulators in clinical practice

Operating a motor vehicle is a complex psychomotor task that requires sustained vigilance. When sleepy, subjects have difficulty maintaining vigilance. As a result, inattention increases the risk of a motor vehicle collision. There is extensive literature that demonstrates that sleepy patients have poor performance and increased motor vehicle crashes. Determining an individual's risk of crash has not been possible solely on clinical grounds and as a result, a number of driving simulators have been developed/employed to aid in this process. While the data shows a consistent effect of sleepiness on driving and simulated driving performance, the role of these simulators in day to day clinical practice is still evolving.

Driver sleepiness and risk of serious injury to car occupants: population based case control study

OBJECTIVES

To estimate the contribution of driver sleepiness to the causes of car crash injuries.

DESIGN

Population based case control study.

SETTING

Auckland region of New Zealand, April 1998 to July 1999.

PARTICIPANTS

571 car drivers involved in crashes where at least one occupant was admitted to hospital or killed ("injury crash"); 588 car drivers recruited while driving on public roads (controls), representative of all time spent driving in the study region during the study period.

MAIN OUTCOME MEASURES

Relative risk for injury crash associated with driver characteristics related to sleep, and the population attributable risk for driver sleepiness.

RESULTS

There was a strong association between measures of acute sleepiness and the risk of an injury crash. After adjustment for major confounders significantly increased risk was associated with drivers who identified themselves as sleepy (Stanford sleepiness score 4-7 v 1-3; odds ratio 8.2, 95% confidence interval 3.4 to 19.7); with drivers who reported five hours or less of sleep in the previous 24 hours compared with more than five hours (2.7, 1.4 to 5.4); and with driving between 2 am and 5 am compared with other times of day (5.6, 1.4 to 22.7). No increase in risk was associated with measures of chronic sleepiness. The population attributable risk for driving with one or more of the acute sleepiness risk factors was 19% (15% to 25%).

CONCLUSIONS

Acute sleepiness in car drivers significantly increases the risk of a crash in which a car occupant is injured or killed. Reductions in road traffic injuries may be achieved if fewer people drive when they are sleepy or have been deprived of sleep or drive between 2 am and 5 am.

Sleepy driving: accidents and injury

OBJECTIVE

The study goals were to evaluate the associated risks of driving and to assess predictors of accidents and injury due to sleepiness.

STUDY DESIGN

A cross-sectional Internet-linked survey was designed to elicit data on driving habits, sleepiness, accidents, and injuries during the preceding 3 years. Statistical analysis included logistic models with covariate-adjusted P values of <0.01 (odds ratios and 95% confidence intervals or limits). Independent accident predictors were sought.

RESULTS

Responses from 10,870 drivers were evaluated. The mean +/- SD age was 36.9 +/- 13 years; 61% were women and 85% were white. The Epworth Sleepiness Scale overall baseline score was 7.4 +/- 4.2 (for drivers with no accidents) and ranged to 12.7 +/- 7.2 (for drivers with > or = 4 accidents) (P = < 0.0001). Twenty-three percent of all respondents experienced > or = 1 accident. Among respondents who reported > or = 4 accidents, a strong association existed for the most recent accident to include injury (P < 0.0001). Sleep disorders were reported by 22.5% of all respondents, with a significantly higher prevalence (35%, P = 0.002) for drivers who had been involved in > or = 3 accidents.

CONCLUSION

Factors of sleepiness were strongly associated with a greater risk of automobile accidents. Predictors were identified that may contribute to accidents and injury when associated with sleepiness and driving.