Do self‐reports provide valid information about driving fitness in seniors?

Aging goes along with cognitive deficits even in healthy seniors. Some of these deficits (e.g. processing speed) are closely related to driving fitness. Consequently, driving fitness also decreases with advancing age. As neurodegenerative disorders further deteriorate cognitive performance in seniors, driving fitness is particularly challenged in this population. Nevertheless, the official driving guidelines for neurodegenerative disorders are rather vague in Germany. This is insofar surprising because neurodegenerative disorders are associated with severe cognitive decline and necessarily lead to a complete loss of driving fitness eventually. Still, there are the same standards for people with Alzheimer’s disease, for example, as for healthy seniors. These standards include self-examination and precautionary measures meaning that German seniors are self-responsible for their driving fitness and have to take precautions if necessary. Noteworthy, Alzheimer’s disease is often associated with a reduced insight into the illness (anosognosia) including a valid judgment of own cognitive abilities (Vogel et al., 2004). As a consequence, many demented people often still drive despite severe driving-related cognitive deficits. Certainly, these drivers pose a high risk for themselves and the driving public which makes their identification an important necessity. Commonly, practical driving lessons are regarded as the gold standard to identify impaired drivers. However, practical driving lessons require immense financial, personnel and temporal resources which go beyond daily clinical routines. An alternative option might be the utilization of questionnaires in which drivers furnish particulars about their driving behaviour. One example is the Driver Behaviour Questionnaire (DBQ; Reason et al., 1990). In the DBQ, traffic lapses, errors and violations within the last 12months are enquired. Previous findings showed that the number of self-reported traffic offences was positively correlated with the number of self-induced accidents (de Winter and Dodou, 2010). However, the validity of self-reports appears to be at least questionable. In the context of a bigger project including 42 driving seniors (mean age= 70.3 +/ 9.1 years) who consulted our memory clinic to clarify possible cognitive deficits, we therefore examined the association between self-reported driving behaviour, driving-related cognitive performance and global cognition. Self-reported driving behaviour was assessed with the 24-item version of the DBQ (Parker et al., 1995), global cognitive functioning with the mini-mental state examination and driving-related cognitive functions with the Corporal test system (Berg and Schubert, 1999). The Corporal test system is a neuropsychological test battery permitted by law to assess driving-related cognitive domains such as diffuse attention, focused spatial attention and divided spatial attention. Contrary to previous findings, conservative nonparametric correlation analyses revealed positive correlations between the Corporal total score and the number of reported DBQ violations (τ=0.50, p=0.003) and between the mini-mental state examination score and the number of reported DBQ violations (τ=0.39, p=0.027). All other correlations failed to reach statistical significance but showed similar patterns (mostly positive correlations). These results indicate that driving seniors with better driving-related cognitive performance and higher global cognitive status in general reported more traffic offences. A plausible reason for these unexpected results may be that seniors with higher cognitive abilities are able to provide more valid judgments of their own fitness to drive (Vogel et al., 2004). An alternative explanation could be that seniors with mild cognitive deficits are aware of possible driving-related constraints and make false statements for fear of losing their driving license. Either way, the present results suggest that self-reports of driving seniors should be interpreted with caution and that the evaluation of driving fitness should be based upon objective measures. Besides practical driving lessons, such measures could involve specific cognitive tests or a multifactorial selection of risk factors as suggested by several working groups.