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Sleep debt, sleepiness and accidents among males in the general population and male professional drivers

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Abstract

Men from the general population and male professional lorry and bus drivers were surveyed with regard to sleep habits and motor vehicle and other types of accidents. A random sample of 4000 men in the general population of Dalarna County in mid-Sweden were mailed a questionnaire and served as referents. A total of 1389 male professional lorry and bus drivers from this county responded to the same questionnaire. A total of 161 of the drivers also underwent a sleep study in their homes.

The proportion of total accidents was higher among the professional drivers as compared with the males in the population, P=0.03. Reports on traffic accidents were the same in both groups, but the professional drivers reported more accidents at leisure compared with referents, P<0.0001. Accidents of any kind, traffic accidents included, among those affected by both snoring and apneas, were not reported more in either of the groups. At the sleep study, 17% of those examined received the diagnosis of obstructive sleep-apnea syndrome (OSAS).

The professional drivers reported proportionally more sleep debt than the referents, P<0.001. Among referents, traffic accidents at leisure, traffic accidents while commuting and accidents at work increased in proportion to sleep debt (P<0.001, 0.006 and 0.002, respectively). The finding that self-perceived sleep debt may have an adverse effect on males in the general population and male professional drivers concerning accident likelihood should have an impact on prevention. These results stress the need to educate the general population on the importance of complying with our biological need of sleep.

Introduction

Sleepiness and reduced vigilance are important risk factors for accident proneness at work (Åkerstedt, 1994). Leger (1994) calculated that as many as 52.5% of all work-related accidents in 1988 in US were potentially related to sleepiness. Sleepiness and sleep disturbances have been shown to increase the frequency of occupational accidents (Ulfberg et al., 2000, Lindberg et al., 2001). Driver alertness may have a great impact on safety. Sleepiness and reduced vigilance are hypothesized to reduce the capability of a driver to function in the traffic milieu.

Numerous factors contribute to fatigue and sleepiness but knowledge about the relations between these factors and accidents continues to be limited. Several studies (George et al., 1987, Findley et al., 1988, Haraldsson et al., 1990) have shown a 2–12-fold greater rate of driving accidents in patients with snoring and obstructive sleep-apnea syndrome (OSAS) than in subjects without sleep-apnea. On the other hand, according to a recent review by Connor et al. (2001) there are few accurate studies on the relationship between disordered sleep and traffic accidents. These authors also found that the direct epidemiological evidence for a causal role of fatigue in car crashes is weak.

In a North American survey, long-haul truck drivers are reported to have obtained 2 h less sleep than required to stay alert in the job (Mitler et al., 1997). Arnold et al. (1997) reported on significant sleep debt among professional drivers in an Australian state, and recently it was also reported that self-reported short sleep was predictive of falling asleep at the wheel (McCartt et al., 2000).

In this study, we assessed the accident likelihood in different situations in daily life among male professional drivers and males in the general population according to sleep-disordered breathing and self-reported sleep debt. The Ethics Committee of the Faculty of Medicine, Uppsala University approved the study.

Section snippets

Professional drivers

The names and addresses of essentially all male professional long-haul lorry and bus drivers, aged 18–64 years, in Dalarna County were obtained through organisations representing employees and employers. A total of 1827 names and addresses were obtained. Each person was mailed a questionnaire (described later). One and two months following the initial mailing, non-responders were sent reminders with additional questionnaires. A total of 1389 individuals were eligible for inclusion in the study.

Results

The professional drivers were heavier than the referents; mean BMI among the drivers was 26.9 versus 26 among the referents (P<0.001). The mean ESS score among the drivers was 7.1 versus 6.7 among the referents (P=0.02). Snoring sometimes per week/daily was reported by 30.6% of the drivers and 29.8% by the referents (NS). Apneas witnessed by spouses were reported by 14% of the professional drivers and 10.7% of the referents (P=0.04).

Among the professional drivers, 36.6% reported accidents in at

Discussion

The data obtained in this study give further support to the hypothesis that sleep debt is common among professional drivers. The results also indicate that self-perceived sleep debt is directly related to accident likelihood for males in the general population and male professional drivers. However, our results did not corroborate earlier data claiming that sleep-disordered breathing is a risk factor for involvement in both traffic and other kinds of accidents.

A previous epidemiological study

Acknowledgements

The research described in this paper was supported by a grant from the Swedish Council for Work Life Research. We thank Jan Ifver for assistance with statistical calculations.

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