Sleep Disorders and Anxiolytics Increase the Risk of Traffic Accidents

abstract & commentary

Source: Teran-Santos J, et al. The association between sleep apnea and the risk of traffic accidents. N Engl J Med 1999; 340:847-851.

Based on simulated driving tests, obstructive sleep apnea has been thought to increase automobile accidents by as much as two- to three-fold when compared with healthy persons (Aldrich MS. Sleep 1989;12:487-494). Teran-Santos and colleagues approach the problem directly, selecting all inter-urban highway drivers involved in traffic accidents and brought to a regional Spanish hospital for immediate treatment. Patients without known chronic illnesses or traffic accidents during the past two months were selected as controls for each above patient involved in a traffic accident. Subjects were questioned for personal habits, diseases, medication, past accidents, and possible causes of drowsiness. Histories of sleep apnea were scaled and tested technically and by low-level nocturnal polygraph. More detailed maneuvers were applied when considered desirable.

Outcomes of 102 case patients and 152 matched controls were compared. Persons who had a clinically abnormal apnea-hypopnea ratio more than 10 had a traffic accident adds rate 4.1 greater than normals. Those who additionally had consumed alcohol on the accident day increased the rate to 11.2.

Psychoactive drugs have often been blamed as contributing to at least 10% of all fatalities in road traffic accidents (De Gier JJ. Maastricht:University of Limburg, Institute for Human Psychopharmacology, 1993). Alcohol carries the greatest dangers, but other psychoactive drugs also may contribute. Barbone and colleagues report from an area in Scotland that 1731 out of 19,386 drivers involved in accidents between August 1, 1992, and June 30, 1995, at least sometimes used a psychoactive drug (Barbone F, et al. Lancet 1998;352:1331-1336).

To be specific: on any given accident day, an average of 189 of the users were taking tricyclic antidepressants, 84 serotonin-reuptake inhibitors, 235 benzodiazepines, and 47 other psychoactive drugs. Only benzodiazepines increased the risk ratio compared to nondrugged drivers’ rate. Overall, adds ratio was 1.62, but the rate was measurably higher in persons younger than 40 years (3.42). Add a positive alcohol test and the odds ratios climbed to 9.55 (n = 4). Barbone et al refer to two reports providing similar results (Ray WA, et al. Am J Epidemiol 1992;136:873-883; Hemmelgarn B, et al. JAMA 1997;278:27-31).


Most studies that identify a relationship between sleep apnea syndromes and traffic accidents reflect the airway-pulmonary obstructive type rather than a faulty central regulation of breathing during sleep. Nevertheless, many neurologists who participate in providing polysomnographic sleep studies or even hear complaints of hypersomnia must warn their patients against driving when feeling drowsy. The dangers of alcohol and anxiolytics must be emphasized. As the data show, these same attitudes must hold for young persons, especially those who combine benzodiazepines with alcohol and sleep deprivation. Therapy that can help outpatients prevent brain trauma is far greater than trying to restore them from traumatic brain injury.