Sleep Disorders and Traffic Accidents

To the Editor: Sleep complaints are common in the general population.1 A growing body of evidence indicates that inadequate sleep results in cognitive impairment.2 Automobile accidents have been shown to be one of the most ominous consequences of insomnia.3 A systematic review found that as many as 20% of traffic accidents were associated with sleep deprivation.4 Some prior studies, however, have relied on self-reported information or had small cohorts or lacked a control group. We conducted a longitudinal nationwide population-based study by analyzing the claim data of Taiwan NHI (National Health Insurance)5 to investigate whether primary insomnia contributes to the incidence and severity of traffic accidents. The study group was selected from people 20 years of age and older, with at least 1 inpatient or 3 outpatient claims for primary insomnia (ICD-9-CM 780.5) during 2002–2006. We excluded those with nonprimary sleep disorders (ICD-9-CM 327) and sleep symptoms related with mental disorders (ICD-9-CM 307.4), as well as those with sleep disorders or traffic accidents between 1996 and 2001. The study group was 1:2 matched, according to sex and age, with a randomly selected control group among those without a sleep disorder. To determine the impact of sleep disorders on the incidence of admission due to traffic accidents, we followed all persons for 2 years or until hospital admission due to traffic accident. To estimate the severity of traffic accidents, we assessed length of admission, incidence of intensive care unit (ICU) admission, length of ICU stay, and inhospital mortality. The study group comprised 59,940 patients and the control group comprised 119,880 persons. The prevalence of sleep disorders requiring medical care rose gradually during the study period, approaching 8% in 2008. Sleep disorders had a female predominance (62% vs. 38%) and peaked at ages 40–49 years (24%). The incidence of traffic accident–related admission was higher among men than among women. The annual incidence of traffic accident-related admission was 44 per 10,000 persons in 1996 and decreased gradually during the study period to 26 per 10,000 persons in 2008. Among all traffic accidents resulting in hospital admission during the study period, 7% involved patients with sleep disorders. We found traffic accident–related admission rates were 49 per 10,000 person-years with sleep disorders and 37 per 10,000 person-years without sleep disorders (Table). Although patients of all ages with sleep disorders were at increased risk of admission due to traffic accidents, the risk was highest for the age groups 30–39 and 40–49. However, the NHI claim data did not include information on whether the patient was the driver or the passenger. Therefore, our result probably underestimates the true impact of sleep disorders on traffic accidents. Except for an increased incidence of ICU admission in patients 50–59 years of age with sleep disorders, we did not find evidence to link severity of traffic accidents to sleep disorders.Table: Association of Hospital Admission Due to Traffic Accidents and Sleep DisordersIn the NHI claim data, patients with sleep disorders had received pharmacologic interventions for an average of 20 days during follow-up (mean 2.0 years). The impact of pharmacologic sleep aids on the incidence of traffic accidents could not be explored in this study and needs further investigation.6 We find that sleep disorders are associated with an increased risk of traffic accidents but not with accident severity. These results may be useful in providing a reference for actuarial calculation by national or commercial insurance companies and in suggesting possibilities for further research. Yi-Ying Chiang Department of Anesthesiology China Medical University Hospital Taichung, Taiwan Department of Health Service Administration College of Public Health China Medical University Taichung, Taiwan Pang-Yao Tsai Management Office for Health Data China Medical University Taichung, Taiwan Pei-Chun Chen Management Office for Health Data China Medical University Taichung, Taiwan College of Public Health China Medical University Taichung, Taiwan Mei-Hui Yang Department of Anesthesiology Lin Shin Hospital Taichung, Taiwan Chi-Yuan Li Department of Anesthesiology China Medical University Hospital Taichung, Taiwan Graduate Institute of Clinical Medical Science College of Medicine China Medical University Taichung, Taiwan Fung-Chang Sung College of Public Health China Medical University Taichung, Taiwan Kuen-Bao Chen Department of Anesthesiology China Medical University Hospital Taichung, Taiwan College of Medicine China Medical University Taichung, Taiwan [email protected]