Estimated cost of crashes in commercial drivers supports screening and treatment of obstructive sleep apnea

Abstract

Sleep apnea among commercial drivers may increase the risk of fall-asleep crashes, which incur large expenses. Drivers of passenger cars whose apnea is treated experience lower crash risk. Among community-based holders of commercial driver's licenses, we considered three methods for identifying sleep apnea syndrome: (1) in-lab polysomnography; (2) selective in-lab polysomnography for high-risk drivers, where high risk is first identified by body mass index, age and gender, followed by oximetry in a subset of drivers; (3) not screening. The costs for each of these three programs equaled the sum of the costs of testing, treatment of identified cases, and crashes. Assuming that treatment prevents apnea-related crashes, polysomnography is not cost-effective, because it was more expensive than the cost of crashes when no screening is done. Screening with BMI, age and gender, however, with confirmatory in-lab polysomnography only on high-risk drivers was cost-effective, as long as a high proportion (73.8%) of screened drivers accepts treatment. These findings indicate that strategies that reduce reliance on in-laboratory polysomnography may be more cost-effective than not screening, and that treatment acceptance may need to be a condition of employment for affected drivers.

Introduction

An appropriate target population for screening for obstructive sleep apnea (OSA) (Gurubhagavatula et al., 2004) is that of commercial drivers. Risk factors for OSA are enriched in this usually male, middle-aged and obese group (Caples et al., 2005). Indeed, OSA is highly prevalent among commercial drivers (Gurubhagavatula et al., 2004, Howard et al., 2004, Stoohs et al., 1995). OSA is associated with daytime sleepiness and, as data from Wisconsin state employees show, impaired psychomotor performance (Kim et al., 1997). This association should be highlighted, as it may predispose affected drivers to experiencing occupational crashes. Data collected from passenger car drivers show that OSA increases vehicular crash rates (American Thoracic Society, 1994, Teran-Santos et al., 1999, Young et al., 1997) and off-road deviations in a driving simulator (Hack et al., 2000). Driving performance (Hack et al., 2000) and crash risk (Cassel et al., 1996, Findley et al., 2000, George, 2001) may improve if affected drivers are identified and treated. These data signal a need for developing screening strategies that find OSA among commercial drivers and assessments to determine whether such strategies are cost-effective.

The standard diagnostic test for OSA is in-laboratory polysomnography, despite its high expense and relative inaccessibility (Pack, 2004, Flemons et al., 2004). We proposed using the alternative of “selective” polysomnography in the highest-risk group of commercial drivers (Gurubhagavatula et al., 2004) by first identifying drivers most likely to have apnea with questionnaire and oximetry (Vazquez et al., 2000). The questionnaire we used, the multivariable apnea prediction (Maislin et al., 1995, Maislin et al., 2003), predicts likelihood of apnea by combining three symptom-frequency questions with body mass index (BMI), age and gender. BMI is a proxy variable for obesity. Oximetry evaluates desaturations during sleep, and can be a sensitive measure of sleep-disordered breathing (Series et al., 1993, Yamashiro and Kryger, 1995, Levy et al., 1996).

In our “two-stage” strategy (Gurubhagavatula et al., 2004, Gurubhagavatula et al., 2001), the multivariable apnea score classified subjects’ risk for OSA as high, low or intermediate. Oximetry was a second-stage test for the subgroup predicted by the questionnaire to be at intermediate risk. Confirmatory sleep studies would be administered selectively to those with high multivariable scores or those with positive oximetry studies. We simulated use of this two-stage strategy in a sleep-disorders clinic with a high prevalence of OSA (Gurubhagavatula et al., 2001), and a community-based sample of commercial drivers (Gurubhagavatula et al., 2004), who may experience increased risk of vehicular accidents due to untreated OSA.

Treatment of OSA may lower crash risk (George, 2001), and thereby lower the cost of crashes. However, even screened drivers may experience “residual” crashes if the program misses cases, or if identified cases do not accept treatment. Employers may bear high costs associated with such crashes (Anon., 2001). A decision to screen based on economics should thus balance expenditures incurred by screening, treatment and residual crashes against the cost of crashes when screening is not done. Such an analysis can help specify the proportion of drivers who must accept treatment in order to offset the costs of the program. If this number is high, then treatment acceptance may need to be a condition for employment of affected drivers.

We now focus on two questions: (1) Is screening cost-effective if we use (a) in-laboratory polysomnography on all drivers or (b) selective polysomnography? (2) What is the minimum rate of treatment acceptance needed for each screening program to be cost-effective? For selective polysomnography, we used a modified two-stage strategy without apnea symptom-reporting, since such reporting may be inaccurate in the occupational setting (N. Hartenbaum, personal communication), and also evaluated an alternative, “one-stage” strategy which did not require oximetry. We chose the cost perspective of the employer, who would bear expenses related to screening, treatment or crashes.