Sleep disorders and accidental risk in a large group of regular registered highway drivers

Abstract

Objective

Despite convincing evidence regarding the risk of highway accidents due to sleepiness at the wheel, highway drivers still drive while sleepy. Sleep disorders can affect driving skills, but the relative impact of sleep complaints among a large population of highway drivers is still unknown.

Methods

Out of 37,648 questionnaires completed by frequent highway users (registered in an electronic payment system), we ran our analyses on 35,004 drivers who responded to all items. The questionnaire previously used in a telephone survey included socio-demographics, driving and sleep disorders items (Basic Nordic Sleep Questionnaire) and the Epworth Sleepiness Scale.

Results

Of all drivers, 16.9% complained of at least one sleep disorder, 5.2% reported obstructive sleep apnea syndrome, 9.3% insomnia, and 0.1% narcolepsy and hypersomnia; 8.9% of drivers reported experiencing at least once each month an episode of sleepiness at the wheel so severe they had to stop driving. One-third of the drivers (31.1%) reported near-miss accidents (50% being sleep-related), 2520 drivers (7.2%) reported a driving accident in the past year, and 146 (5.8%) of these driving accidents were sleep-related. The highest risk of accidents concerned patients suffering from narcolepsy and hypersomnia (odds ratio 3.16, p < .01) or multiple sleep disorders (odds ratio 1.46, p < .001). Other major risk factors were age [18–30 years (OR 1.42, p < .001)] and being unmarried (OR 1.21-fold, p < .01).

Conclusions

In regular highway drivers, sleepiness at the wheel or sleep disorders such as hypersomnia and narcolepsy are responsible for traffic accidents independent of age, sex, marital status or socio-professional categories.

Introduction

Epidemiological studies from the 1990s showed that fatigue and sleep-related accidents represent up to 20% of all traffic accidents in industrial societies [1], [2], [3], [4], [5]. Drowsiness has been identified as the reason behind fatal road crashes and many industrial accidents [6], [7], [8], [9], [10].

Healthy subjects driving in the middle of the night have already demonstrated major driving impairment related to circadian and homeostatic pressure [11], but many drivers are also patients affected by sleep disorders who must face altered driving habits [12].

Sleep disorders are very common in the adult general population [13], [14], [15], [16], [17]. Insomnia concerns one adult out of five [16], [18] and sleep apnea 5–10% [19], [20]. Excessive daytime somnolence is present in about 10% of adults [13], and restless legs syndrome (RLS) in 5–10% of adults [14], [17]. Narcolepsy is a rare disease with less than 0.1% of adults affected [21].

The risk of accidents due to sleep disorders has been extensively studied in patients with sleep apnea [22] with many of the studies showing a 2- to 3-fold increased risk. Rare and limited studies have also compared insomniacs’ risk of accidents to the risk of good sleepers [23], [24]. However, there is less epidemiologic research available on the risk of accidents in hypersomniac and narcoleptic drivers [25], [26], [27] possibly because of the low prevalence of these diseases [25], [26], [28], [29].

Finally, some sleep disorders have been studied as accident risk factors, but these studies were conducted among small patient cohorts, and additive risk factors like profession or driving habits were rarely considered [25], [26].

Recently, Powell et al. [29] used a novel methodology based on Internet interviews to investigate the risk of driving when sleepy. The study clearly showed the predictable risk of near misses related to sleepiness in the occurrence of future sleep-related accidents. They also showed that patients suffering from sleep disorders had more sleep-related accidents but no information was available on the medical status of these patients (treated versus untreated). They also had no information on the origin of the responders because the database was generated by anonymous volunteers asked to fill in a questionnaire after watching an American TV show on sleepiness at the wheel.

Europe differs from the United States in many respects, and the prevalence of sleep disorders, drug intake or poor sleep hygiene may be an area of difference between the two continents. We first conducted a telephone survey based on a representative sample of French drivers [30]. The questionnaires included sociodemographics, driving and sleep disorders items and the Epworth Sleepiness scale. Of 4774 drivers (response rate: 86%), 28% experienced at least one episode of severe sleepiness at the wheel (i.e., requiring them to stop driving) in the previous year; 11% of drivers reported at least one near-miss accident in the previous year (46% sleep-related); 5.8% of drivers reported at least one accident, 5.2% of these being sleep-related (an estimate of 90,000 sleep-related accidents per year in France). Experiencing at least one episode of severe sleepiness at the wheel was strongly associated with near misses (OR 6.50, 95% CI, 5.20–8.12, p < 0.001) and traffic accidents (OR 2.03, 95% CI, 1.57–2.64, p < 0.001) in the past year. Statistical power was not sufficient in this study to assess the impact of rare sleep disorders (i.e., narcolepsy–hypersomnia) on accident risk. We therefore planned a larger epidemiological survey on a sample of frequent highway drivers using the same questionnaire.

The goal of this new study was to investigate the accidental risk of subjects reporting sleep disorders in a French highway drivers population.