Sleep apnea & automobile crashes

Background: As a group, patients with obstructive sleep apnea (OSA) are at increased risk of having automobile accidents. Previous studies using actua l accident data have used only small numbers of subjects. Objective: To determine the rate of automobile accidents in a large populat ion of OSA patients using objective data from the Ministry of Transportatio n of Ontario (MTO). Design: Retrospective study Setting: Academic sleep disorders clinic and laboratory. Participants: Ail cases of OSA polygraphically confirmed between June 1990 and June 1994. Interventions: Gases of OSA were a priori divided into groups based on apne a-hypopnea index (AHI): (OSA1-AHI 10-25, OSA2-AHI 26-40, OSA3-AHI>40) and d riving records were obtained from the MTO. Age and sex matched controls wer e selected at random from drivers in the MTO driver database who hold passe nger vehicle licences. Analysis was restricted to drivers with the same lic ence class. Main Outcome Measures: Primary outcome measure was accidents in the five ye ars preceding diagnosis. Secondary outcome was citations during the same pe riod. Results: There were 155 of 460 OSA patients with one or more accidents comp ared with 150 of 581 Controls for the same time period (x(2)=7.7,p<0.01). T he rate of accidents/year, for the preceding five years, was 0.07+/-0.14 fo r Controls versus 0.09+/-0.14 for OSA ( p <0.05). This difference could all be accounted for by increased accident rate in OSA patients with the highe st AHI (OSA3) ( MVA/yr: 0.11+/-0.15, 0.08+/-0.12, 0.06+/-0.14 for OSA group s 3,2,1 respectively) as there was no differences among Control, OSA1 and O SA2 accident rates. OSA patients had twice as many citations as Controls ( 1.74+/-2.13 vs 0.86+/-1.43 p<0.001) although the types of citation were the same. Conclusions: Increased automobile accidents in OSA may be restricted to cas es with more severe apnea (AHI >40). Despite the large sample size tan orde r of magnitude greater than previous reports using accident data) further s tudy is needed with even larger numbers, including more measures of disease severity and rigorously controlling for driving exposure.