Driving Risks in Obstructive Sleep Apnea (OSA)

It is estimated that 1 in every 15 adults has at least moderate OSA (1). As the risks and ill effects of this condition are further elucidated, physicians are rightly asking, “Who should be restricted from driving?” Equally, the social importance of driving renders them rightly reluctant to recommend driving restrictions. Here then is a brief summary of the evidence relating OSA to motor vehicle accidents (MVAs):

1994 National Commission on Sleep Disorder Research in the USA reported drowsiness is a factor in 36% of fatal MVAs, and 42-54% of all MVAs (2).

1997 Terry Young, leading OSA epidemiologist, reported:

• Males with at least mild OSA [Apnea-Hyponea Index (AHI) = 5] or habitual snoring were significantly more likely to have a crash in a 5 year period,
• Males and females with moderate OSA (AHI = 15) had an odds ratio of 7.3 over controls for multiple crashes over a 5-year period (3).

1999 A Spanish study showed that:

• The drivers of crashed vehicles had an odds ratio of 6.3 for at least mild OSA (AHI = 5) over controls, and that
• The Epworth Questionnaire (for subjective sleepiness) alone failed to identify subjects at higher risk for accidents (4).

2000 A second Spanish study showed:

• Among drivers who often felt sleepy on the road, those with self-reported MVA(s) in the past 5 years, compared with those without crashes, had an odds-ratio of 8.5 for moderate OSA (AHI = 15 with arousal index = 15) (5).

2001 A study from the University of Western Ontario showed:

• The risk of MVAs due to OSA is removed when patients are effectively treated with CPAP (6).

Conclusions

The following guidelines are suggested from the above evidence:

1. Uncorrected moderate or severe OSA (AHI = 15 on polysomnography) is a justifiable reason to restrict driving privileges. In B.C. a physician is required to report such restriction if he/she knows a patient so advised continues to drive.
2. Driving restrictions may safely be lifted once CPAP is being regularly used (at least 6 hrs/night for 6 days/week). Compliance card technology may help with determination; polysomnography is not required. Follow-up is for life, with annual compliance card reports if possible.
3. In patients treated by means other than CPAP, it would seem reasonable to remove driving restrictions once the AHI is reduced to < 15, i.e. OSA is mild. This should be determined by polysomnography.
4. It would seem unreasonable to restrict the driving of mild OSA patients on this evidence. However, males with AHI 5-14 should be warned of the risk, treated and followed.
5. Although sleepiness from all causes is a large factor in MVAs, the Epworth Questionnaire alone fails to effectively identify those at risk. History, examination and oximetry must be considered together. Polysomnography is definitive: if advised and refused driving must be restricted (7).

 

It is important for all drivers to be aware that every doctor in BC is required by law to report to the Superintendant of Motor Vehicles  detalis of anyone who continues to drive after being told by a medical doctor that it is unsafe for him to do so.

Richard R.J. Smyth, M.B.B.S., F.R.C.S.
February 2004
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References

1. Young, T.B. et al. Epidemiology of Obstructive Sleep Apnea. American Journal of Respiratory Critical Care Medicine 2002; 165: 1217-1239.
2. Leger, D. The cost of sleep-related accidents: a report for the National Commission on Sleep Disorders Research. Sleep 1994; 17: 84:93.
3. Young, T.B. et al. Sleep-Disordered Breathing and MVAs. Sleep 1997; 20: 608-613.
4. Terán-Santos, J. et al. The Association Between Sleep Apnea and the Risk of Traffic Accidents. New England Journal of Medicine 1999; 340: 847-851.
5. Masa, J.F. et al. Habitually sleepy drivers have a high frequency of automobile crashes. American Journal of Respiratory Critical Care Medicine 2000; 162: 1407-1412.
6. George, C.F.P. Reduction in motor vehicle collisions following treatment of sleep apnea with nasal CPAP. Thorax 2001; 56: 508-512.
7. Determining medical fitness to drive; 6th ed., CMA publication, p. 25.