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Abstract: Young men figure prominently in sleep-related road crashes. Non-driving studies show them to be particularly vulnerable to sleep loss, compared with older men. We assessed the effect of a normal night''s sleep vs. prior sleep restricted to 5h, in a counterbalanced design, on prolonged (2h) afternoon simulated driving in 20 younger (av. 23y) and 19 older (av. 67y) healthy men. Driving was monitored for sleepiness related lane deviations, EEGs were recorded continuously and subjective ratings of sleepiness taken every 200s. Following normal sleep there were no differences between groups for any measure. After sleep restriction younger drivers showed significantly more sleepiness-related deviations and greater 4–11Hz EEG power, indicative of sleepiness. There was a near significant increase in subjective sleepiness. Correlations between the EEG and subjective measures were highly significant for both groups, indicating good self-insight into increasing sleepiness. We confirm the greater vulnerability of younger drivers to sleep loss under prolonged afternoon driving. [Copyright &y& Elsevier]

Abstract: Objectives: To examine the effects on monotonous driving of normal sleep versus one night of sleep restriction in continuous positive airway pressure (CPAP) treated obstructive sleep apnoea (OSA) patients compared with age matched healthy controls. Methods: Nineteen CPAP treated compliant male OSA patients (OSA-treated patients (OPs)), aged 50–75years, and 20 healthy age-matched controls underwent both a normal night’s sleep and sleep restriction to 5h (OPs remained on CPAP) in a counterbalanced design. All participants completed a 2h afternoon monotonous drive in a realistic car simulator. Driving was monitored for sleepiness-related minor and major lane deviations, with ‘safe’ driving time being total time driven prior to first major lane deviation. EEGs were recorded continuously, and subjective sleepiness ratings were taken at regular intervals throughout the drive. Results: After a normal night’s sleep, OPs and controls did not differ in terms of driving performance or in their ability to assess the levels of their own sleepiness, with both groups driving ‘safely’ for approximately 90min. However, after sleep restriction, OPs had a significantly shorter (65min) safe driving time and had to apply more compensatory effort to maintain their alertness compared with controls. They also underestimated the enhanced sleepiness. Nevertheless, apart from this caveat, there were generally close associations between subjective sleepiness, likelihood of a major lane deviation and EEG changes indicative of sleepiness. Conclusions: With a normal night’s sleep, effectively treated older men with OSA drive as safely as healthy men of the same age. However, after restricted sleep, driving impairment is worse than that of controls. This suggests that, although successful CPAP treatment can alleviate potential detrimental effects of OSA on monotonous driving following normal sleep, these patients remain more vulnerable to sleep restriction. [Copyright &y& Elsevier]

Investigates the effectiveness of 200 milligrams of caffeine in preventing early morning driver sleepiness. Prevalence of sleep-related vehicle accidents in the early morning; Reduction in driving incidents in the first 30 minutes and subjective sleepiness in the first hour after caffeine intake.

Previous research has shown that caffeine and a<15-min nap effectively and separately reduce sleepiness in drivers for 1 hr. in the present study, we examined in 12 sleepy individuals the treatments combined, taken during a 30-min break, prior to a longer (2 hr) continuous monotonous afternoon drive in a car simulator. Nonnap comparisons were 200 mg caffeine only and placebo. For placebo, driving incidents, subjective and electroencephalographic measures of sleepiness all reflected a mid-afternoon peak. This peek was significantly reduced by caffeine and eliminated by the combined treatment, which reduced incidents to 9% of placebo levels versus 34% of placebo levels for caffeine alone. Naps comprising "nonsleep dozing" were still effective. [ABSTRACT FROM AUTHOR]

Following night-time sleep restriction, afternoon driving performance during the bi-circadian surge in afternoon sleepiness is markedly worsened by blood alcohol concentrations (BACs) well under most national driving limits. This study assessed how driving with this same sleep restriction and BACs (av 40 mg and 28 mg alcohol/100 ml blood at the beginning and end of drive, respectively) respond during the evening circadian rise in alertness. In a 2 × 2 (alcohol versus control drink [double blind] × normal night sleep versus sleep restricted), repeated-measures design, eight healthy young men drove for 2 h from 18:00 h, in a real-car simulator, on a monotonous, simulated highway. Driving impairment (lane drifting), subjective sleepiness and EEG measures of sleepiness were recorded. While sleep restriction alone produced significant impairments to evening driving and subjective sleepiness, alcohol alone did not. However, alcohol combined with sleep restriction significantly worsened all indices, although, this was less than that found for afternoon driving with identical interventions. Whereas low BACs may not affect driving in normally alert drivers in the early evening, the addition of moderate sleep restriction still produces a dangerous combination. Probably, there is no ‘safe’ level of alcohol intake for otherwise sleepy drivers, at any time of the day. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The aim of the present study was to examine the effect of mild hypohydration on performance during a prolonged, monotonous driving task. Methods: Eleven healthy males (age 22 ± 4 y) were instructed to consume a volume of fluid in line with published guidelines (HYD trial) or 25% of this intake (FR trial) in a crossover manner. Participants came to the laboratory the following morning after an overnight fast. One hour following a standard breakfast, a 120 min driving simulation task began. Driver errors, including instances of lane drifting or late breaking, EEG and heart rate were recorded throughout the driving task Results: Pre-trial body mass ( P = 0.692), urine osmolality ( P = 0.838) and serum osmolality ( P = 0.574) were the same on both trials. FR resulted in a 1.1 ± 0.7% reduction in body mass, compared to − 0.1 ± 0.6% in the HYD trial ( P = 0.002). Urine and serum osmolality were both increased following FR ( P < 0.05). There was a progressive increase in the total number of driver errors observed during both the HYD and FR trials, but significantly more incidents were recorded throughout the FR trial (HYD 47 ± 44, FR 101 ± 84; ES = 0.81; P = 0.006) Conclusions: The results of the present study suggest that mild hypohydration, produced a significant increase in minor driving errors during a prolonged, monotonous drive, compared to that observed while performing the same task in a hydrated condition. The magnitude of decrement reported, was similar to that observed following the ingestion of an alcoholic beverage resulting in a blood alcohol content of approximately 0.08% (the current UK legal driving limit), or while sleep deprived. [ABSTRACT FROM AUTHOR]

Purpose: Driver error is the largest cause of road traffic accidents, accounting for around 68% of all vehicle crashes in the UK. During long and monotonous driving, most individuals display progressive signs of visual fatigue and a loss of vigilance. Since deficits in total body water (TBW) are associated with altered mood and decrements in aspects of cognitive function, it is possible that dehydrated drivers may be more susceptible to errors in judgement and car handling. With this in mind, the aim of the present study was to examine the effects of fluid restriction, on performance during a prolonged, monotonous driving task. Methods: Eleven healthy males (age 22 ± 4 y) completed a familiarisation trial, before two experimental trials were undertaken in a randomised manner. Each experimental trial took place over two days. On day 1 volunteers were instructed to consume a volume of fluid in line with published guidelines (HYD trial) or 25% of this intake (FR trial). Participants came to the laboratory the following morning after an overnight fast (day 2). One hour following a standard breakfast, a 120 min driving simulation task began. During the HYD trial volunteers were provided with 200 mL of fluid every hour, and on the FR trial only 25 mL was made available each hour. Body mass, serum and urine osmolality, and subjective feelings were recorded during trials. Driver errors, including instances of lane drifting or late breaking, brain activity (EEG) and heart rate were recorded throughout the driving task. Results: Pre-trial body mass (P=0.692), urine osmolality (P=0.838) and serum osmolality (P=0.574) were the same on both trials. FR resulted in a 1.1±0.7% reduction in body mass, compared to -0.1±0.6% in the HYD trial (P = 0.002). Urine and serum osmolality were both increased following FR (P<0.05). EEG alpha and theta activity increased throughout both HYD and FR trials (P = 0.038), indicative of reduced vigilance, but no clear difference was apparent between the trials (P=0.062). There was a progressive increase in the total number of driver errors observed during both the HYD and FR trials, but significantly more incidents were recorded throughout the FR trial (HYD 47 ± 44, FR 101 ± 84; ES = 0.81; P = 0.006). Conclusions: The results of the present study suggest that mild hypohydration, resulted in an increase in errors during a prolonged, monotonous drive, compared to that observed while performing the same task in a hydrated condition. The magnitude of decrement reported was similar to that observed following the ingestion of alcohol resulting in a blood alcohol content of approximately 0.08% (the current UK legal driving limit), or while sleep deprived. There is no question that both drink-driving and driving while tired increases the risk of road traffic accidents, and many countries have instigated national campaigns to educate drivers of the associated risks. Given the present findings, perhaps some attention should also be directed to encouraging appropriate hydration practices among drivers. [ABSTRACT FROM AUTHOR]