Sleep disorders, sleepiness and the risk of traffic accidents

The aim of this thesis was to identify the prevalence of sleep disorders, mainly obstructive sleep apnea (OSA), among public transport operators (PTO s). Further to assess the risk of motor vehicle accident (MVA) in a group of patients with suspected OSA compared with the general population. Additionally, we aimed to identify specific risk factors linked to a history of MVA in these patients and to assess the prevalence of such factors in a large European sleep apnea patient database. We also determined the interventional effect of continuous positive airway pressure (CPAP) treatment on hypersomnolence, neurocognitive function and history of traffic accident. Finally, we investigated functional cognitive markers associated with history of MVA among PTO s as well as single and multi-center cohorts of patients with OSA. The study used objective and subjective methods to assess sleep, sleep disorders, hypersomnia, vigilance and daytime cognitive performance. Data was extracted from a nationwide traffic accident registry (STRADA) for individual identification of MVA history. Sleep disorders including OSA, excessive daytime sleepiness, insomnia and restless legs syndrome (25%, 13%, 10% and 2%, respectively) were prevalent among PTO s (n=87). Among clinical patients (n=1478) with suspected OSA the estimated risk of MVA was 2.5 times higher than in the matched general population. Measures of hypersomnolence, use of hypnotics, short sleep time, and driving distance (OR 2.0 to 2.7, p≤0.02) were associated with MVA risk, whereas conventional metrics of OSA severity were not. Compared with the general population, OSA patients were 1.9 times more likely to be injured in the MVA (p=0.01). We identified functional measures of neurocognitive dysfunction associated with MVA history (p<0.01). A mean nightly CPAP use of at least 4.0 hours was associated with improved neurocognitive function, reduced hypersomnia and a 70% reduction of MVA. It is concluded that conventional metrics of OSA are insufficient for the recognition of risk while markers of neurocognitive function may provide better identification of patients at risk. Our findings suggest that the high risk of MVA in OSA and the effectiveness of treatment in terms of accident reduction call for effective programs for detection and treatment of OSA.