Steering simulation performance in patients with obstructive sleep apnoea and matched control subjects

Comparing the Driving Skills of Adolescents with Obstructive Sleep Apnea to Healthy Controls: The Results of a Case-Controlled Observational Study

Auto crashes are a leading cause of death and injury among adolescents. Untreated obstructive sleep apnea (OSA) can cause sleepiness and inattention, which could negatively impact novice drivers, but OSA-related studies have focused on older drivers. This study used a driving simulator to examine whether licensed 16-19-year-old adolescents with OSA have diminished driving skills. Twenty-one adolescents with OSA and twenty-eight without OSA (both confirmed using polysomnography) completed two randomly ordered driving trials in a simulator (with induced distractions versus without). A mixed ANOVA examined the between-subjects effect of the OSA group, the within-subjects effect of the distraction condition, and the group-by-condition interaction effect on the ability to maintain lane position and the frequency of extended eye glances away from the roadway. T-tests were also used to examine group differences in reported sleepiness and inattention during daily life. The distraction task increased extended off-road glances and difficulties maintaining lane position (p < 0.001). However, adolescents with OSA did not display worse eye glance or lane position than controls and there were no significant group-by-condition interactions. Although the groups differed on polysomonographic features, there were also no significant differences in reported sleepiness or inattention. The distraction task negatively impacted both groups of adolescent drivers, but those with OSA did not fare differentially worse. Most adolescents in our study had mild OSA (median obstructive apnea-hypopnea index = 4.4), the most common form in the community. It remains possible that youth with more severe OSA would show increased driving impairment.

European Respiratory Society statement on sleep apnoea, sleepiness and driving risk

Obstructive sleep apnoea (OSA) is highly prevalent and is a recognised risk factor for motor vehicle accidents (MVA). Effective treatment with continuous positive airway pressure has been associated with a normalisation of this increased accident risk. Thus, many jurisdictions have introduced regulations restricting the ability of OSA patients from driving until effectively treated. However, uncertainty prevails regarding the relative importance of OSA severity determined by the apnoea–hypopnoea frequency per hour and the degree of sleepiness in determining accident risk. Furthermore, the identification of subjects at risk of OSA and/or accident risk remains elusive. The introduction of official European regulations regarding fitness to drive prompted the European Respiratory Society to establish a task force to address the topic of sleep apnoea, sleepiness and driving with a view to providing an overview to clinicians involved in treating patients with the disorder. The present report evaluates the epidemiology of MVA in patients with OSA; the mechanisms involved in this association; the role of screening questionnaires, driving simulators and other techniques to evaluate sleepiness and/or impaired vigilance; the impact of treatment on MVA risk in affected drivers; and highlights the evidence gaps regarding the identification of OSA patients at risk of MVA.

Precision teaching to improve drivers' lane maintenance

INTRODUCTION

This study investigates the effect of precision teaching signals on lane maintenance.

METHODS

In experiment 1, the control group drove a simulator with no signals. In experiment 2, drivers were presented with auditory signals depending on their position within or outside the lane. In experiment 3, visual signals were presented in addition to auditory signals to examine the effect of redundancy on drivers' lane maintenance.

RESULTS

Results showed an improvement in lane maintenance in experiment 2. Cross-experiment analysis indicated this effect not to be the result of learning. Data from experiment 3 also showed that presenting redundant signals did not further reduce lane variability or help drivers maintain a more central position within the lane.

CONCLUSIONS

Taken together, data suggest precision teaching be effective as an educational tool to improve lane maintenance. Practical Applications: Our study shows the potential for precision teaching to serve as a valuable tool in driver training.

Assessment of Sleepiness in Drivers: Current Methodology and Future Possibilities

Many patients with obstructive sleep apnea syndrome (OSAS) drive a vehicle both for pleasure and as part of their employment. Some, but not all, patients with OSAS are at increased risk of being involved in road traffic accidents. Clinicians are often asked to make recommendations about an individual's fitness to drive, and these are likely to be inconsistent in the absence of objective criteria. This article discusses the current practice of the assessment of individuals' sleepiness with respect to driving, the limitations of available techniques, and future possibilities.

Factors that affect simulated driving in patients with obstructive sleep apnoea

Patients with obstructive sleep apnoea syndrome (OSAS) are at increased risk of involvement in road traffic accidents (RTAs) [1]. Clinicians diagnosing OSAS need to advise patients about driving but there are no validated tools and no robust objective data about which factors are important [2]. There are position statements, based solely on expert opinion, from various professional bodies [3–6]. In general, they conclude that a patient with significant daytime sleepiness and a recent RTA or near miss attributable to sleepiness, fatigue or inattention, should be considered a high-risk driver [3–6]. In a recent survey using clinical vignettes, we have shown that there is considerable variability in the advice that patients are likely to receive [7]. This indicates that clinicians require more robust guidance.

Objective data for advising sleep apnoea sufferers whether they are at increased risk of an accident when drivinghttp://ow.ly/TWPgm

Impact of overnight traffic noise on sleep quality, sleepiness, and vigilant attention in long-haul truck drivers: Results of a pilot study

This study aimed to evaluate the impact of traffic noise along the motorway on sleep quality, sleepiness, and vigilant attention in long-haul truck drivers. This was a randomized, crossover, within-subject controlled study. Healthy long-haul truck drivers spent 6 consecutive nights in a real truck berth with full sleep laboratory equipment. During 3 nights, subjects were exposed to replayed traffic noise alongside motorways, whereas the other 3 nights were without traffic noise. Polysomnography was recorded during the nights and numerous sleepiness tests and vigilance examinations were performed during the following standardized working day. Outcome measures were compared between noisy and silent nights using the paired Wilcoxon test. Ten healthy long-haul truck drivers with a mean age of 36.3 ± 7.3 years completed the study as planned. On noisy nights, subjects had greater latencies to the rapid eye movement (REM) phase (90 ± 32 min vs 69 ± 16 min, P = 0.074) and higher percentages of sleep stage 1 (13.7 ± 5.5% vs 11.2 ± 4.4%; P = 0.059). Subjects also rated their sleep quality as having been better during nights without noise (28.1 ± 3.7 vs 30.3 ± 6.2, P = 0.092). The impact of these differences on daytime sleepiness and vigilance was rather low; however, mean Karolinska Sleepiness Scale (KSS) scores measured during the course of the following day were higher on six out of eight occasions after noisy nights. The effects of overnight traffic noise on sleep quality are detectable but unlikely to have any major impact on the vigilant attention and driving performance of long haul-truck drivers with low nocturnal noise sensitivity. This might not be true for subgroups prone to sleeping disorders.

Obstructive sleep apnea in North American commercial drivers

The most common medical cause of excessive daytime sleepiness (EDS) is obstructive sleep apnea (OSA). Specifically, among an estimated 14 million US commercial drivers, 17-28% or 2.4 to 3.9 million are expected to have OSA. Based on existing epidemiologic evidence, most of these drivers are undiagnosed and not adequately treated. Untreated OSA increases the risk of vehicular crashes as documented in multiple independent studies and by meta-analysis. Therefore, identifying commercial drivers with OSA and having them effectively treated should decrease crash-related fatalities and injuries. Several strategies are available for screening and identifying drivers with OSA. The simplest and most effective objective strategies use body mass index (BMI) cutoffs for obesity. Functional screens are promising adjuncts to other objective tests. The most effective approach will likely be a combination of a good questionnaire; BMI measures; and a careful physician-obtained history complemented by a functional screen.

Are nocturnal breathing, sleep, and cognitive performance impaired at moderate altitude (1,630-2,590 m)?

STUDY OBJECTIVES

Newcomers at high altitude (> 3,000 m) experience periodic breathing, sleep disturbances, and impaired cognitive performance. Whether similar adverse effects occur at lower elevations is uncertain, although numerous lowlanders travel to moderate altitude for professional or recreational activities. We evaluated the hypothesis that nocturnal breathing, sleep, and cognitive performance of lowlanders are impaired at moderate altitude.

DESIGN

Randomized crossover trial.

SETTING

University hospital at 490 m, Swiss mountain villages at 1,630 m and 2,590 m.

PARTICIPANTS

Fifty-one healthy men, median (quartiles) age 24 y (20-28 y), living below 800 m.

INTERVENTIONS

Studies at Zurich (490 m) and during 4 consecutive days at 1,630 m and 2,590 m, respectively, 2 days each. The order of altitude exposure was randomized. Polysomnography, psychomotor vigilance tests (PVT), the number back test, several other tests of cognitive performance, and questionnaires were evaluated.

MEASUREMENTS AND RESULTS

The median (quartiles) apnea-hypopnea index at 490 m was 4.6/h (2.3; 7.9), values at 1,630 and 2,590 m, day 1 and 2, respectively, were 7.0/h (4.1; 12.6), 5.4/h (3.5; 10.5), 13.1/h (6.7; 32.1), and 8.0/h (4.4; 23.1); corresponding values of mean nocturnal oxygen saturation were 96% (95; 96), 94% (93; 95), 94% (93; 95), 90% (89; 91), 91% (90; 92), P < 0.05 versus 490 m, all instances. Slow wave sleep on the first night at 2,590 m was 21% (18; 25) versus 24% (20; 27) at 490 m (P < 0.05). Psychomotor vigilance and various other measures of cognitive performance did not change significantly.

CONCLUSIONS

Healthy men acutely exposed during 4 days to hypoxemia at 1,630 m and 2,590 m reveal a considerable amount of periodic breathing and sleep disturbances. However, no significant effects on psychomotor reaction speed or cognitive performance were observed.

CLINICAL TRIALS REGISTRATION

Clinicaltrials.gov: NCT01130948.

High-risk of obstructive sleep apnea and excessive daytime sleepiness among commercial intra-city drivers in Lagos metropolis

BACKGROUND

The burden of obstructive sleep apnea among commercial drivers in Nigeria is not known.

AIM

To assess the prevalence of high risk of obstructive sleep apnea (OSA) and excessive daytime sleepiness (EDS) among intra-city commercial drivers.

SETTING AND DESIGN

A descriptive cross-sectional study in three major motor parks in Lagos metropolis.

MATERIALS AND METHODS

Demographic, anthropometric and historical data was obtained. The risk of OSA and EDS was assessed using the STOP BANG questionnaire and the Epworth Sleepiness Scale, respectively.

STATISTICAL ANALYSIS

The relationship between the OSA risk, EDS risk and past road traffic accident (RTA) was explored using the Pearson's chi square. Independent determinants of OSA risk, EDS risk and past RTA, respectively, were assessed by multiple logistic regression models.

RESULT

Five hundred male commercial drivers (mean age (years) ±SD = 42.36 ± 11.17 and mean BMI (kg/m(2)) ±SD = 25.68 ± 3.79) were recruited. OSA risk was high in 244 (48.8%) drivers and 72 (14.4%) had EDS. There was a positive relationship between OSA risk and the risk of EDS (Pearson's X(2) = 28.2, P < 0.001). Sixty-one (12.2%) drivers had a past history of RTA but there was no significant relationship between a past RTA and either OSA risk (X(2) = 2.05, P = 0.15) or EDS risk (X(2) = 2.7, P = 0.1), respectively. Abdominal adiposity, regular alcohol use and EDS were independent determinants of OSA risk while the use of cannabis and OSA risk were independent determinants of EDS. No independent risk factor for past RTA was identified.

CONCLUSION

A significant proportion of commercial drivers in Lagos metropolis are at high risk of OSA and EDS.

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.

Driving-Related Neuropsychological Performance in Stable COPD Patients

Background. Cognitive deterioration may impair COPD patient's ability to perform tasks like driving vehicles. We investigated: (a) whether subclinical neuropsychological deficits occur in stable COPD patients with mild hypoxemia (PaO(2) > 55 mmHg), and (b) whether these deficits affect their driving performance. Methods. We recruited 35 stable COPD patients and 10 normal subjects matched for age, IQ, and level of education. All subjects underwent an attention/alertness battery of tests for assessing driving performance based on the Vienna Test System. Pulmonary function tests, arterial blood gases, and dyspnea severity were also recorded. Results. COPD patients performed significantly worse than normal subjects on tests suitable for evaluating driving ability. Therefore, many (22/35) COPD patients were classified as having inadequate driving ability (failure at least in one of the tests), whereas most (8/10) healthy individuals were classified as safe drivers (P = 0.029). PaO(2) and FEV1 were correlated with almost all neuropsychological tests. Conclusions. COPD patients should be warned of the potential danger and risk they face when they drive any kind of vehicle, even when they do not exhibit overt symptoms related to driving inability. This is due to the fact that stable COPD patients may manifest impaired information processing operations.

Cognition in obstructive sleep apnea-hypopnea syndrome (OSAS): current clinical knowledge and the impact of treatment

Obstructive sleep apnea-hypopnea syndrome (OSAS) is characterized by the presence of disordered breathing events that occur during sleep, as well as symptoms such as sleepiness and snoring. OSAS is associated with a number of adverse health consequences, and a growing literature focuses on its cognitive correlates. Although research in this field is mixed, multiple studies indicate that OSAS patients show impairment in attention, memory, and executive function. Continuous positive airway pressure (CPAP) is the most effective and widely used treatment of OSAS, and supplemental medications may supplement CPAP treatment to ameliorate associated symptoms. Here, we review the literature on OSAS and cognition, including studies that have investigated the impact of CPAP and stimulant medication on cognitive performance in patients with OSAS. In general, no consistent effect of CPAP use on cognitive performance was evident. This may be due, in part, to variability in study design and sampling methodology across studies. Studies of stimulant medications generally reported positive effects on cognitive performance. We conclude with a discussion of the mechanisms that have been proposed to explain cognitive dysfunction in OSAS and directions for future research.

Reliability of a single objective measure in assessing sleepiness

STUDY OBJECTIVES

To evaluate reliability of single objective tests in assessing sleepiness.

DESIGN

Subjects who completed polysomnography underwent a 4-nap multiple sleep latency test (MSLT) the following day. Prior to each nap opportunity on MSLT, subjects performed the psychomotor vigilance test (PVT) and divided attention driving task (DADT). Results of single versus multiple test administrations were compared using the intraclass correlation coefficient (ICC) and adjusted for test administration order effects to explore time of day effects. Measures were explored as continuous and binary (i.e., impaired or not impaired).

SETTING

Community-based sample evaluated at a tertiary, university-based sleep center.

PARTICIPANTS

372 adult commercial vehicle operators oversampled for increased obstructive sleep apnea risk.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

AS CONTINUOUS MEASURES, ICC WERE AS FOLLOWS: MSLT 0.45, PVT median response time 0.69, PVT number of lapses 0.51, 10-min DADT tracking error 0.87, 20-min DADT tracking error 0.90. Based on binary outcomes, ICC were: MSLT 0.63, PVT number of lapses 0.85, 10-min DADT 0.95, 20-min DADT 0.96. Statistically significant time of day effects were seen in both the MSLT and PVT but not the DADT. Correlation between ESS and different objective tests was strongest for MSLT, range [-0.270 to -0.195] and persisted across all time points.

CONCLUSIONS

Single DADT and PVT administrations are reliable measures of sleepiness. A single MSLT administration can reasonably discriminate individuals with MSL < 8 minutes. These results support the use of a single administration of some objective tests of sleepiness when performed under controlled conditions in routine clinical care.

Driving simulator performance remains impaired in patients with severe OSA after CPAP treatment

STUDY OBJECTIVES

To assess the effectiveness of CPAP treatment in improving 90-minute driving simulator performance in severe OSA patients compared to age/gender matched controls.

DESIGN

Driving simulator performance was assessed at baseline and 3 months later, with OSA patients treated with CPAP during the interval.

SETTING

University Teaching Hospital.

PARTICIPANTS

Patients with severe OSA (n = 11) and control subjects without OSA (n = 9).

INTERVENTIONS

CPAP MEASUREMENTS AND RESULTS: Simulator driving parameters of steering deviation, braking reaction time and crashes were measured at baseline and ∼3 months follow-up. At baseline, OSA subjects demonstrated significantly greater steering deviation compared to controls (mean [95% CI], OSA group, 49.9 cm [43.7 to 56.0 cm] vs control group, 34.9 cm [28.1 to 41.7 cm], p = 0.003). Following ∼3 months of CPAP treatment (mean ± SD 6.0 ± 1.4 h/night), steering deviation in OSA subjects improved by an average of 3.1 cm (CI, 1.4 to 4.9), p < 0.001, while no significant steering changes were observed in the control group. Despite the improvement, steering deviation in the OSA group remained significantly higher than in controls (OSA group, 46.7 cm [CI, 40.6 to 52.8 cm] vs control group, 36.1 cm [CI, 29.3 to 42.9 cm], p = 0.025).

CONCLUSIONS

While driving simulator performance improved after ∼3 months of CPAP treatment with high adherence in patients with severe OSA, performance remained impaired compared to control subjects. These results add to the growing body of evidence that some neurobehavioral deficits in patients with severe OSA are not fully reversed by treatment. Further studies are needed to assess causes of residual driving simulator impairment and to determine whether this is associated with persistent elevated real-life accident risk.

TRIAL REGISTRATION

Data presented in this manuscript was collected as part of a clinical trial "Experimental Investigations of Driving Impairment in Obstructive Sleep Apnoea" ACTRN12610000009011, http://www.anzctr.org.au/trial_view.aspx?ID=334979

Effects of alcohol on attention orienting and dual-task performance during simulated driving: an event-related potential study

Driving is a complex task and is susceptible to inattention and distraction. Moreover, alcohol has a detrimental effect on driving performance, possibly due to alcohol-induced attention deficits. The aim of the present study was to assess the effects of alcohol on simulated driving performance and attention orienting and allocation, as assessed by event-related potentials (ERPs). Thirty-two participants completed two test runs in the Divided Attention Steering Simulator (DASS) with blood alcohol concentrations (BACs) of 0.00%, 0.02%, 0.05%, 0.08% and 0.10%. Sixteen participants performed the second DASS test run with a passive auditory oddball to assess alcohol effects on involuntary attention shifting. Sixteen other participants performed the second DASS test run with an active auditory oddball to assess alcohol effects on dual-task performance and active attention allocation. Dose-dependent impairments were found for reaction times, the number of misses and steering error, even more so in dual-task conditions, especially in the active oddball group. ERP amplitudes to novel irrelevant events were also attenuated in a dose-dependent manner. The P3b amplitude to deviant target stimuli decreased with blood alcohol concentration only in the dual-task condition. It is concluded that alcohol increases distractibility and interference from secondary task stimuli, as well as reduces attentional capacity and dual-task integrality.

Novice drivers' performance after different alcohol dosages and placebo in the divided-attention steering simulator (DASS)

RATIONALE

The divided-attention steering simulator (DASS) is designed to measure lane-keeping (i.e., a tracking task using a steering wheel) while performing a secondary visual task (responding to digits that appear in the corners of the computer screen). Some studies have already used the DASS, but the magnitude of impairment is difficult to interpret because reference values are lacking.

OBJECTIVE

To examine the magnitude of impairment after administration of four different dosages of alcohol and placebo.

MATERIALS AND METHODS

Thirty-two healthy young adults participated in this randomized, single-blind crossover trial. Subjects received alcohol to gain a blood alcohol concentration (BAC) of 0.02%, 0.05%, 0.08%, and 0.10% or alcohol-placebo. Sixteen subjects performed a 30-min test in DASS (dual-task condition). Outcome measures were steering error, reaction time, and percentage of errors. Sixteen other subjects performed the test without performing the secondary peripheral task (single-task condition).

RESULTS

Twenty-eight subjects (novice drivers; drivers' license up to 5 years) were included in the analyses. Dose-dependent impairment was found in both the single-task condition (F ((4,11)) = 10.86, p < 0.001) and the dual-task condition (F ((4,9)) = 5.58, p < 0.015). Performance at all BAC levels differed significantly (p < 0.05) from alcohol-placebo, except BAC 0.02%. With increasing BAC levels, subjects made more errors and reacted slower on the peripheral visual search task, but these effects did not reach significance.

CONCLUSION

With increasing BAC, dose-dependent impairment was found. The DASS seems to be a suitable divided-attention task that is useful in psychopharmacological research and training of novice drivers.

Daytime driving simulation performance and sleepiness in obstructive sleep apnoea patients

BACKGROUND

Sleepiness related car accidents are common in obstructive sleep apnoea syndrome (OSAS) patients. The objective measurements of sleepiness used in clinical setting quantify the tendency to fall asleep in quiet situations that are completely different from driving.

METHODS

We studied 30 OSAS patients with subjective (subjective sleepiness scales) and objective (multiple sleep latency test, MSLT) sleepiness measurements, associated with driving simulation test (DST), previously validated in young healthy subjects. The results of subjective and objective sleepiness tests were compared with simulated driving performance in order to evaluate the suitability of our DST for measuring alertness.

RESULTS

Subjective and objective sleepiness measurements were significantly correlated with driving performance on the simulator. The most significant correlates of sleepiness were the measures of the primary vehicle control task on the simulator: lane position variability and crash data. The comparison of DST and MSLT results suggested our driving simulated approach could be used to evaluate daytime sleepiness in the clinical setting of OSAS patients.

CONCLUSIONS

Our DST is a suitable objective tool to detect sleepiness in OSAS patients, and could be useful in the clinical setting of sleep medicine and research.

Simulated driving in obstructive sleep apnoea-hypopnoea; effects of oral appliances and continuous positive airway pressure

Impaired simulated driving performance has been demonstrated in obstructive sleep apnoea-hypopnoea syndrome (OSAHS) patients. Although continuous positive airway pressure (CPAP) generally improves simulated driving performance, the effects of oral-appliance (OA) therapy are unknown. The aims of this study were to determine to what extent OSAHS patients have more difficulty with a monotonous simulated driving test when compared with control subjects and to compare the effects of OA with CPAP therapy. Simulated driving performance was evaluated in 20 OSAHS patients and 16 control subjects during a 25-min driving test. After randomization, ten patients started OA and CPAP therapy, respectively. After 2 to 3 months of treatment, patients repeated the driving test. At baseline, the total number of lapses of attention during driving was significantly higher in OSAHS patients as compared with control subjects. As a result of treatment, the total number of lapses of attention was significantly decreased in both the OA and CPAP group. When comparing driving performance between the OA and CPAP group, no significant differences were noted. OSAHS patients perform worse on a simulated driving test when compared with control subjects. When evaluating the effects of treatment, adequate OSAHS management with either OA or CPAP therapy usually resulted in substantial improvements of simulated driving. Conclusions beyond both treatments improving simulated driving performance are, however, not justified by the data in the present study.

Event-related potentials and secondary task performance during simulated driving

Inattention and distraction account for a substantial number of traffic accidents. Therefore, we examined the impact of secondary task performance (an auditory oddball task) on a primary driving task (lane keeping). Twenty healthy participants performed two 20-min tests in the Divided Attention Steering Simulator (DASS). The visual secondary task of the DASS was replaced by an auditory oddball task to allow recording of brain activity. The driving task and the secondary (distracting) oddball task were presented in isolation and simultaneously, to assess their mutual interference. In addition to performance measures (lane keeping in the primary driving task and reaction speed in the secondary oddball task), brain activity, i.e. event-related potentials (ERPs), was recorded. Performance parameters on the driving test and the secondary oddball task did not differ between performance in isolation and simultaneous performance. However, when both tasks were performed simultaneously, reaction time variability increased in the secondary oddball task. Analysis of brain activity indicated that ERP amplitude (P3a amplitude) related to the secondary task, was significantly reduced when the task was performed simultaneously with the driving test. This study shows that when performing a simple secondary task during driving, performance of the driving task and this secondary task are both unaffected. However, analysis of brain activity shows reduced cortical processing of irrelevant, potentially distracting stimuli from the secondary task during driving.

The psychophysiological determinants of fatigue

Driver fatigue is a major risk for road accidents that can often result in injury and death. However, considerable debate still exists concerning factors associated with driver fatigue. Because of the complex nature of fatigue, this paper reports a study that investigated both physiological and psychological determinants of fatigue. Three fatigue outcome measures were used, including a physiological, psychological and a combined physiological and psychological measure. Fifty participants performed a driving simulator task till they showed symptoms of fatigue and were assessed before and after the task. Significant factors associated with physiological fatigue included higher levels of baseline delta activity and an extraverted personality. Factors related to the psychological fatigue outcome measure included sleepiness, low healthy lifestyle status, an extraverted personality and tension-prone personality, and negative mood states. The combined fatigue outcome measure was associated with factors such as a tension-prone and extraverted personality, low systolic blood pressure, and negative mood states. The findings emphasize the importance of assessing fatigue using a range of outcome measures in order to achieve a thorough understanding of what factors contribute to fatigue and highlight the need to develop fatigue countermeasures that employ a broad range of measures.

Sustained attention measurements in obstructive sleep apnea and risk of traffic accidents

The aim of this study was to identify associations between performance on driving simulators, subject sleep complaints, and risk of traffic accidents in a population undergoing OSAS investigation.

PATIENTS AND METHODS

One hundred and twenty-nine consecutive adult patients with a driver's licence and clinical symptoms of OSA were initially recruited from the hospital waiting list. Each patient was applied a polysomnography and two driving tests. Patients also completed a Basic Nordic Sleep Questionnaire, Epworth Sleepiness Scale and SF-36 quality of life questionnaire.

RESULTS

Poor performance in vigilance was associated with alcohol intake (OR 4.41, 95% CI 1.13-17.20, P<0.05), and SF-36 vitality dimension (OR 0.97, 95% CI 0.94-0.99, P<0.05). Poor tracking error was associated with female gender (OR 6.79, 95% CI 1.37-33.65, P<0.05), alcohol intake (OR 3.32, 95% CI 1.03-10.63, P<0.05), and a history of accidents in the previous year (OR 5.84, 95% CI 1.33-25.68, P<0.05). Poor reaction time was only associated with age (OR 1.12, 95% CI 1.03-1.21, P<0.01). When all three performance measures were studied jointly, only reaction time was associated with self-reported dozing while driving (OR 5.39, 95% CI 1.10-26.32, P<0.05), and irresistible tendency to fall asleep was associated with poor tracking error (P<0.05).

CONCLUSIONS

Performance on driving simulators is associated with some sleep complaints in OSA patients. Although these measures are not directly associated to traffic accidents, they are, in fact, associated to related circumstances such as dozing while driving and falling asleep while driving.

Performance on a dual driving simulation and subtraction task following sleep restriction

A novel task, combining simulated driving with subtraction, was compared in 26 participants ages 18 to 26 years (M=20.6, SD=2.3; 13 men). After two nights of 8.5 hr. in bed, participants performed a 30-min. driving and subtraction task followed by a 10-min. Psychomotor Vigilance Task. These tasks were repeated after two more nights of 8.5 hr. time in bed for the control group and 5 hours and 3 hours time in bed for the restricted group. The sensitivity of the task to moderate sleep loss was supported because impairment was seen on several dual-task variables whereas impairment was not observed on the Psychomotor Vigilance Task.

The role of sleep-disordered breathing, daytime sleepiness, and impaired performance in motor vehicle crashes-a case control study

STUDY OBJECTIVE

To examine levels of sleep-disordered breathing, daytime sleepiness, and impaired performance in 60 motor vehicle crash drivers and 60 controls matched for age, gender, and body mass index.

MEASUREMENTS AND RESULTS

All participants underwent polysomnography and daytime function assessments. Cases reported significantly higher levels of driver sleepiness (% sleepiness: mean +/- SD; cases: 26 +/- 17%; controls: 16 +/- 12%; p = 0.003) and demonstrated slower reaction times on a sustained attention task ( p = 0.02). There was a trend for more objective sleepiness in cases (maintenance of wakefulness test: cases: 17 +/- 4 minutes; controls: 18 +/- 3 minutes, p = 0.06) despite no differences in general subjective sleepiness (Epworth score: cases: 8 +/- 4; controls: 8 +/- 4; p = 0.93). There were no significant differences in polysomnography measures between groups (apneas + hypopneas per hour slept: cases: 8 +/- 9; controls: 9 +/- 16; p = 0.89; arousals per hour slept: cases: 18 +/- 8; controls: 21 +/- 12; p = 0.11).

CONCLUSION

Crash drivers demonstrated significantly more driver sleepiness, slower reaction times and a trend for greater objective sleepiness compared with well-matched controls. However, the findings in crash drivers were independent of medical causes of sleep fragmentation, with both cases and controls showing moderate levels of unrecognized mild sleep-disordered breathing. Crash prevention strategies should focus on increasing personal awareness of the risks of sleepiness behind the wheel in all individuals.

Sleep. 5: Driving and automobile crashes in patients with obstructive sleep apnoea/hypopnoea syndrome

Driving is a complex task involving distinct cognitive, perceptual, motor, and decision making skills. After placing the vehicle on the road, the driver must constantly survey the ever changing roadway environment to keep the vehicle in the lane and moving at an appropriate safe speed. This surveillance involves two distinct visual tasks: estimating and responding to the oncoming curvature and controlling lane position. Driving is therefore a divided attention task involving speed and lane control as well as monitoring. To do this in a safe manner requires careful attention and alertness which can be problematic for patients with obstructive sleep apnoea/hypopnoea syndrome (OSAHS) or other sleep disorders.

Pharmacotherapies for Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is common, causes considerable morbidity and probably contributes to mortality particularly through associated cardiovascular disease. The physical therapy of continuous positive airway pressure (CPAP) is extremely effective in the majority of patients but most patients would prefer an alternative. Intuitively, OSA should be amenable to pharmacotherapy. The upper airway of affected individuals can be narrowed but is patent during wakefulness. Collapse of the airway during sleep occurs when negative intra-luminal pressure generated by inspiratory effort exceeds the tone of the upper airway dilators. This mismatch may be in part due to respiratory drive instability but the state-dependent fall in drive to the airway dilator muscles is the biggest factor in most patients. Various drugs have been investigated as treatment for OSA. Acetazolamide, theophylline, nicotine, opioid antagonists and medroxyprogesterone have been used to increase respiratory drive. Clonidine has been tested with the aim of reducing rapid eye movement sleep when OSA is often most severe. Various antidepressants have been used to suppress rapid eye movement sleep and to preferentially activate the upper airway dilators. The drug trials have often been of poor design and none has included more than a few patients. Most of the drugs have been found to be ineffective and those that have worked for some patients (acetazolamide and protriptyline) have produced intolerable adverse effects. There have been recent advances in the understanding of the neurotransmitters involved in the control of sleep and the upper airway motor neurones, offering the possibility of novel approaches to the drug treatment of OSA for those patients who cannot tolerate or do not benefit from CPAP. It seems likely that a better understanding of the mechanisms of OSA in individual patients and tailoring of drug therapy will be the way forward.

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.

The effect of sleep disruption on performance of anaesthetists--a pilot study

Fatigue has been implicated in the occurrence of critical incidents. Using a driving simulator to assess vigilance, we investigated the effect of sleep disruption on the ability of anaesthetists to maintain vigilance after a night on-call. Following an undisturbed night of sleep, subjects demonstrated a significant improvement in their vigilance scores. Subjects failed to demonstrate this following a disturbed night. The timing of disturbance had a bearing on performance. Subjects' performance was worse if their sleep had been disturbed in the first third of the night. The effect of sleep disruption on vigilance has implications for patient safety during anaesthesia.

The hazards and prevention of driving while sleepy

In the present paper the literature bearing on the association between sleepiness and driving is reviewed and the current state of prevention is discussed. Sleepiness may be a factor in about 20% of motor vehicle accidents and studies carried out in controlled environments suggest that the most common changes in driving performance attributable to sleepiness include increased variability of speed and lateral lane position. Higher-order functions including judgement and risk taking may also deteriorate. Moreover, prolonging wakefulness even by a few hours may produce deterioration in driving performance comparable to that seen in drivers with blood alcohol concentrations at levels deemed dangerous by legislation. The majority of prevention efforts to date have focussed on short-term solutions that only mask underlying sleepiness and it is suggested that more emphasis be directed toward primary prevention efforts such as educating drivers about the importance of getting sufficient sleep and avoiding circadian performance troughs. Finally, the important role that health professionals can play in the identification, treatment, and education of sleepy drivers is highlighted.

Prevalence of snoring and sleep-disordered breathing in a group of commercial bus drivers in Hong Kong

OBJECTIVES

To assess the prevalence of sleep-disordered breathing (SDB) and its associated symptoms in a group of commercial bus drivers in Hong Kong.

METHODS

Two hundred and sixteen of 410 bus drivers from three different shifts were interviewed with the Sleep & Health Questionnaire (SHQ) and the Epworth sleepiness scale (ESS) at a Hong Kong bus depot. Seventeen subjects from each shift were then randomly selected for at-home sleep study using the Mesam IV device (Madaus Medizin-Elektronik, Freiburg, Germany).

RESULTS

There were 207 men and nine women (mean age 42.4 +/- 7.5 years; body mass index (BMI) 25.4 +/- 4.5 kg/m2; ESS 5.3 +/- 4.2). From the SHQ it was discovered that: (i) daytime sleepiness was reported by 87 subjects (40%), (ii) snoring > or = 3 times per week was reported by 80 subjects (37%), (iii) witnessed apnoea was reported by 17 subjects (7.9%) and (iv) 29 subjects (13.4%) reported having fallen asleep during driving. Among the 51 subjects who underwent the at-home sleep study: (i) 31 subjects (61%) had respiratory disturbance index (RDI) > or = 5 per hour of sleep, (ii) 21 subjects (41%) had RDI > or = 10 per hour of sleep, (iii) 12 subjects (24%) had RDI > or = 15 per hour of sleep and (iv) 35 subjects (68.6%) snored objectively > or = 10% of the night. Ten subjects (20%) had RDI > or = 5 and sleepiness at work, while five subjects (9.8%) had RDI > or = 5 and ESS > 10. No significant differences were noted in the SHQ responses, ESS, objective snoring or RDI among the three groups. Multiple regression analysis showed that BMI and witnessed apnoea were the only positive independent predictors of RDI.

CONCLUSIONS

This study showed a high prevalence of objective snoring and SDB in a group of commercial bus drivers. Neither self-reported sleepiness nor the ESS could identify subjects with SDB.

Daytime sleepiness and its evaluation

Basic models of sleepiness, focusing on the homeostatic and circadian components of sleepiness, are able to predict important fluctuations of sleepiness. However, they fail in explaining certain sleepiness phenomena, as for instance in insomnia patients. To meet this shortcoming, modern models incorporate the arousal component of sleepiness, in addition to the sleep drive. While these models mainly concentrate on short-term changes in sleepiness, "state" sleepiness, there are indications that a stable characteristic level of sleepiness, "trait" sleepiness, is also an important determinant of a person's level of sleepiness. This leads to a conceptualization of sleepiness in which situational factors modify a basal level of sleep drive and arousal. It implies that sleepiness is not a unitary concept and can reflect essentially different states. Multiple sleepiness assessment tools have been proposed in the past. The majority of them offer valuable information, but they do not grasp all aspects of sleepiness. We should bear in mind that tools for assessing sleepiness are always operationalizations reflecting the theoretical framework the investigator has on sleepiness. Hence, rather than searching for a gold standard for the measurement of sleepiness, future research effort should be aimed at linking the various measurement techniques with the hypothesized underlying components of sleepiness on a sound empirical basis.

Driving accident frequency increased in patients with multiple sclerosis

OBJECTIVES

To assess the influence of multiple sclerosis (MS) on the ability to drive safely.

MATERIAL AND METHODS

A 10-year historical cohort register-study on 197 patients with MS and 545 controls individually matched on age, gender, place of residence, and exposure period. Persons with other neurological diseases, diabetes or abuse were excluded. The outcome measure was treatment at the emergency department after accident as a car driver.

RESULTS

Five patients and four controls had been treated, the rate per 1000 person-years with exposure being 3.4 times higher (CI 0.73-17.15) in the patients than in the control cohort. The difference is significant in one-sided test (P=0.04).

CONCLUSION

Drivers with MS were treated more often than healthy controls at a casualty department after having a road traffic accident. However, drastic consequences regarding the patients automobile driving should be avoided until these results have been substantiated by further investigations.

Cognitive dysfunction in sleep disorders

Fifty-six studies were reviewed that explored cognitive dysfunctions in people with sleep-related breathing disorders (SRBD, 24 studies), insomnia (18 studies), or narcolepsy (14 studies). Individual study outcomes were grouped according to neuropsychological functions. Available evidence was reviewed separately for SRBD, insomnia and narcolepsy. Consistent evidence was found for impaired driving simulation performance in SRBD patients (92.9% of comparisons with control subjects). Other neuropsychological functions with less pronounced impairment included (i) attention span, divided attention and sustained attention for SRBD patients; (ii) attention span, verbal immediate memory and vigilance for insomniac patients, and (iii) sustained attention, vigilance and driving simulation performance for narcoleptic patients. Reduced performance in tasks measuring attention was found to be higher for SRBD and narcoleptic patients (35.9% and 44.2% of all comparisons, respectively) while this rate was lower for insomniac patients (22.8%). Impairment of memory performance in comparison with control subjects was less pronounced for all three groups, with 20.0% for insomnia, 17.1% for SRBD and 15.6% for narcolepsy. In other areas of cognitive functioning, the data did not allow definite conclusions for any of the patient groups.

Relationship between obstructive sleep apnoea, driving simulator performance, and risk of road traffic accidents

BACKGROUND

Obstructive sleep apnoea (OSA) has been shown to be associated with an increased risk of road traffic accidents (RTAs). Predicting the driving ability and risk of RTAs in an individual with OSA is difficult. On-road testing is the gold standard, but this is time consuming, expensive, and potentially dangerous. Simple computer based driving simulators have been developed to help determine driving ability. Although patients with OSA have been shown to perform poorly compared with matched controls, it is not known whether these simulators can predict those at most risk of accidents. In this study we evaluated whether data derived from a simple driving simulator provided information over and above that obtained from the history and a sleep study that might be useful for advising patients about driving.

METHODS

We examined 150 patients admitted for routine sleep studies for investigation of OSA and snoring. Each patient performed a 20 minute driving simulation and completed a questionnaire regarding their driving history and experience.

RESULTS

Logistic regression analysis was used to investigate factors associated with patients' performance on the simulator. It was found that patient characteristics, older age (OR 1.05, 95% CI 1.01 to 1.09, p<0.01), female sex (OR 9.32, 95% CI 1.09 to 79.4, p<0.04), and self-reported alcohol consumption (OR 1.04, 95% CI 1.01 to 1.07, p<0.01) had the greatest influence; however, the number of self-reported near miss accidents was independently associated with a poor performance (OR 2.62, 95% CI 1.00 to 6.88, p<0.05). A further logistic regression was used to investigate whether clinical history, sleep study results, and data from the driving simulator were useful in classifying patients with OSA as having had an RTA. The number of off-road events per hour on the simulator was independently associated with a history of previous RTA (OR 1.004, 95% CI 1.0004 to 1.008, p<0.03). The Epworth score was independently associated with episodes of falling asleep at the wheel (OR 1.21, 95% CI 1.12 to 1.31, p<0.00001) and near miss accidents (OR 1.15, 95% CI 1.07 to 1.23, p<0.0001). Using this model, 100% of patients who did not have an accident could be identified, but only 10% of those who did.

CONCLUSIONS

Although factors not directly related to OSA influence performance on a driving simulator, there is an independent relationship between driving ability in patients with OSA and performance on a simple computer based simulator. When combined with clinical history, it is those not reporting hypersomnolence and not having off-road events on the simulator who appear to be at least risk of adverse driving events. Poor performance on the simulator, however, relates poorly to accident history. These data require confirmation in future studies before simple computer simulators can be used in clinical practice to advise whether an individual is safe to drive.

Comparison of the effects of sleep deprivation, alcohol and obstructive sleep apnoea (OSA) on simulated steering performance

Patients with obstructive sleep apnoea (OSA) are reported to have an increased risk of road traffic accidents. This study examines the nature of the impairment during simulated steering in patients with OSA, compared to normal subjects following either sleep deprivation or alcohol ingestion. Twenty-six patients with OSA and 12 normal subjects, either deprived of one night's sleep or following alcohol ingestion [mean (SD) alcohol blood level 71.6 mg dl(-1) (19.6)], performed a simulated steering task for a total of 90 min. Performance was measured using the tendency to wander (SD), deterioration across the task, number of 'off-road' events and the reaction time to peripheral events. Control data for OSA, sleep deprivation and alcohol were obtained following treatment with nasal continuous positive airway pressure (nCPAP), after a normal night of sleep, and following no alcohol, respectively. Patients with untreated OSA, and sleep-deprived or alcohol-intoxicated normal subjects performed significantly less well, compared to their respective controls (P<0.01 for all tests), with untreated OSA lying between that of alcohol intoxication and sleep deprivation. Alcohol impaired steering error equally throughout the whole drive, whilst sleep deprivation caused progressive deterioration through the drive, but not initially. Untreated OSA was more like sleep deprivation than alcohol, although there was a wide spread of data. This suggests that the driving impairment in patients with OSA is more compatible with sleep deprivation or fragmentation as the cause, rather than abnormal cognitive or motor skills.

Outcome measurement in sleep medicine practice and research. Part 2: assessment of neurobehavioral performance and mood

Neurobehavioral performance and alterations in mood consequent to sleep disorders and their treatment has recently been the focus of clinical investigations. Primarily in patients with obstructive sleep apnea (OSA), there has been increased interest in the effects of sleep fragmentation and hypoxemia on the brain's ability to process information and to alter affect. The purpose of the second part of this two-part series is to describe measures that could be applied to document the impact of sleep disorders on neurobehavioral performance and mood, discuss factors affecting the selection of measures for research and practice, and to describe evidence generated by the use of these instruments in research. The neurobehavioral deficits that accompany sleep deprivation can be categorised as decrements in cognitive throughput, working memory and sustained attention. Usually evaluated using tasks of short duration, impairments associated with OSA have included impaired information processing and decline in the total number of completed and/or correct responses per unit time. Using assessments of working memory, including short recall maneuvers involving words or paragraphs, investigators have documented in sleep apnea patients the inability to consolidate and recall material producing deficits in the recollection and retention of new information. Evaluations of sustained attention appraise reaction time, the ability to remain on task, and the number of errors of omission and false responses. Evidence suggests that OSA patients display slowing of response time as well as increased errors, lapses and number of false responses. Similar deficits have been documented with sustained and divided attention tasks that present the respondent with challenges in tracking and reaction response, tasks required for driving. Although untreated sleep apnea patients were more impaired than normal controls, their performance on such tasks was greatly enhanced following CPAP treatment. In addition to substantial clinically meaningful improvements in many areas of neurobehavioral performance, changes in mood have also accompanied treatment for sleep apnea. 2001 Harcourt Publishers Ltd