Electroencephalographic correlates of on-the-road driving fatigue in untreated insomniac patients

Introduction Insomnia patients consistently self-reported daytime fatigue and cognitive impairments which could contribute to traffic crashes. However, the model of hyperarousal was proposed to explain the lack of objective evidence of cognitive dysfunction in patients with primary insomnia because of the contribution of psychological and physiological arousal to daytime functioning. In this case it is not clear that insomnia patients could suffer from sleepiness which could contribute to traffic crashes. Electroencephalography recordings during driving were previously used to assess sleepiness and fatigue during a driving task. It appeared that an increase in the theta, alpha and beta band is linked to a higher fatigue. We expected that insomnia patients will not have a decrement in their driving performance associated with EEG correlates of less fatigue. The purpose of the present study was thus to compare the electroencephalographic correlates of sleepiness and fatigue during a driving task in insomniac patients and in good sleepers. Materials and methods Nineteen older insomniacs and nineteen older good sleepers were included in the study (aged between 55–75 years). After a sleep recording night in the sleep unit, the participants performed an on-the-road highway driving task in the morning. The vehicle’s speed and lateral position were continuously recorded. Electroencephalography was also recorded during the driving task. The main driving parameter was the standard deviation of the lateral position (SDLP), which is an index of weaving; the standard deviation of speed (SDS) was also quantified. The fatigue EEG correlates were assessed by quantification of the absolute power spectra in the theta, alpha and beta bands. Results Results for the SDLP and the SDS reveal that driving performance was not impaired in the insomnia group in comparison to the good sleepers group. Preliminary analysis of EEG recordings reveal that good sleepers had a higher power spectrum in the theta, alpha and beta bands. Conclusion It is concluded that older chronic insomnia patients appear to be able to successfully perform a one hour highway driving task in real traffic. EEG results suggested that insomniacs were less fatigued than good sleepers which could explain the lack of difference in the driving performance. This could be in line with the hyperarousal model proposed to explain to lack of cognitive dysfunction in insomnia patients. Acknowledgements We want to thanks Anita Van Oers for the driving data analyses, Henk Brauers and Jo Gorissen as driving instructors and student assistants for the help in the data collection.