Saturday, August 28, 2010

Recent car crash or fender bender? Truck crash? Check your sleep.

Obstructive Sleep Apnea and Risk of Motor Vehicle Crash: Systematic Review and Meta-Analysis

Of all occupations in the United States, workers in the trucking industry experience the third highest fatality rate, accounting for 12% of all worker deaths. In 2006, there were 368,000 police-reported large truck crashes, resulting in 4,321 fatalities and 77,000 injuries.1 The Federal Motor Carrier Safety Administration (FMCSA) was established as a separate administration within the U.S. Department of Transportation (DOT) pursuant to the Motor Carrier Safety Improvement Act of 1999. The primary mission of the FMCSA is to reduce crashes, injuries and fatalities involving large trucks and buses. Among the strategies employed by the FMCSA to accomplish this goal are the development and maintenance of medical fitness standards for drivers of commercial vehicles; these standards are applied by medical examiners to commercial drivers, who are required by Federal statute to undergo medical qualification examinations at least every 2 years.
Obstructive sleep apnea (OSA) is a prevalent and potentially dangerous condition among commercial motor vehicle (CMV) drivers. While OSA is conservatively estimated to affect approximately 5% of the general population,2 the condition appears to be much more prevalent in commercial drivers. Howard et al. estimated that 50% of more than 3000 commercial drivers were at risk for sleep apnea.3 Pack et al. found that 28.2% of 406 commercial drivers had at least mild sleep apnea and 4.7% had severe sleep apnea by conventional criteria.4 The majority of research indicates that OSA is a significant cause of motor vehicle crashes.3,59 Thus, assessment of the risk of OSA and development of effective methods to identify and treat commercial drivers with OSA is an important part of the mission of the FMCSA. Since the most recent standards for medical examiners regarding OSA are from a Federal Highway Administration (FHWA) sponsored conference in 1991,10 these standards required an evidence-based update.
The current study was designed to provide evidence for updating the standards by conducting a systematic review of the relevant literature concerning OSA and CMV drivers. The literature consists predominantly of cohort and case-control studies. Given that few studies specifically enroll CMV drivers, studies that included non-CMV drivers were also evaluated.
The primary objective of this study was to determine whether individuals with OSA are at an increased risk for a motor vehicle crash when compared to individuals without OSA. If so, a secondary objective was to identify disease-related factors associated with an increased motor vehicle crash risk.

DESIGN/SETTING: Seven electronic databases (MEDLINE, PubMed (PreMEDLINE), EMBASE, PsycINFO, CINAHL, TRIS, and the Cochrane library) were searched (through May 27, 2009), as well as the reference lists of all obtained articles. We included controlled studies (case-control or cohort) that evaluated crash risk in individuals with OSA. We evaluated the quality of each study and the interplay between the quality, quantity, robustness, and consistency of the body of evidence, and tested for publication bias. Data were extracted by 2 independent analysts. When appropriate, data from different studies were combined in a fixed- or random-effects meta-analysis.

RESULTS: Individuals with OSA are clearly at increased risk for crash. The mean crash-rate ratio associated with OSA is likely to fall within the range of 1.21 to 4.89. Characteristics that may predict crash in drivers with OSA include BMI, apnea plus hypopnea index, oxygen saturation, and possibly daytime sleepiness.

CONCLUSIONS: Untreated sleep apnea is a significant contributor to motor vehicle crashes.

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