Time course of changes in driving simulator performance with and without treatment in patients with sleep apnoea hypopnoea syndrome.

BACKGROUND Improvements in driving simulator performance have been demonstrated in patients with sleep apnoea hypopnoea syndrome (SAHS) after several months of treatment, but it is not known how quickly these improvements are achieved and lost. The aim of this study was to assess the time course of changes in driving simulator performance in patients with SAHS following treatment with continuous positive airways pressure (CPAP). METHODS Eighteen patients with severe SAHS performed a driving simulator test at baseline (before treatment) and at days 1, 3, and 7 of a 2 week CPAP trial period. CPAP was then discontinued and the patients performed three further driving simulator tests after 1, 3, and 7 days. Eighteen patients with severe SAHS acted as controls and performed the driving simulator test on seven occasions in a pattern similar to that of the treated patients. RESULTS Significant improvements in tracking error (p=0.004), reaction time (p=0.036), and the number of off road events per hour (p=0.032) were seen in the CPAP treated group compared with the controls at 7 days. Following discontinuation of CPAP for 7 days a significant difference in driving simulator performance persisted between the two groups, but the size of the difference had reduced. CONCLUSION Driving simulator performance in patients with severe SAHS improves within the first few days of starting CPAP and these improvements appear to be sustained for up to 1 week after withdrawal. Further data about the usefulness of driving simulators in predicting safe driving are needed before these results can be used in advising patients on driving. However, the data appear to suggest that driving can be safely resumed after a few days of effective CPAP treatment.