Relationship between cognitive failures, sleepiness and road traffic incidents in patients with untreated obstructive...

Current guidelines emphasise assessing "excessive sleepiness" and severity of sleep disordered breathing (SDB) when advising patients with obstructive sleep apnoea about driving. However, accidents can occur due to lack of concentration and poor reactions. The Cognitive Failures Questionnaire (CFQ) measures self-reported cognitive deficits in the completion of simple everyday tasks. We investigated the relationship between drivers' cognitive capability and the severity of SDB, sleepiness and self-reported driving incidents.

348 patients (n=150, exploratory; n=198, validation) considered for a trial of continuous positive airway pressure and 173 controls (exploratory (n=105), validation (n=68)) matched for age and driving experience completed questionnaires that included the CFQ and a driving questionnaire.

Compared to controls, patients had a higher total mean±sd CFQ score (37±18 versus 28±12, p=<0.0001, 95% CI -13.3- -7.3) and more self-reported driving incidents (accidents and/or near misses in the last year) (38% versus 10%; OR 2.6, 95% CI 2.79-8.34; p=0.0005). Sleepiness, rather than severity of SDB, predicted a higher CFQ score in patients compared to controls, both in the exploratory and validation cohorts. Self-reported driving incidents were significantly more frequent in patients who reported a higher degree of sleepiness (Epworth Sleepiness Score (ESS) >10 40% versus ESS <10 20%, OR 2.6, 95% CI 1.5-4.5; p=0.0005). CFQ score was also a predictor of driving incidents.

Sleepiness and cognitive dysfunction, rather than severity of SDB, predicts driving incident risk. The CFQ may identify a different aspect of accident risk and therefore may be useful in assessing fitness to drive in patients with obstructive sleep apnoea syndrome.