Date:
August 9, 2005
Promotors:
Prof. J.L. Kenemans, MD, PhD
Prof. B. Olivier, MD, PhD
Prof. C.J. Kalkman, MD, PhD
Co-promotor:
E.R. Volkerts, MD, PhD
Chronic pain is a major public health care problem and is one of the most common reasons to seek medical consultation. The core theme of this thesis was to assess cognitive deficits in chronic pain patients due to pain and its analgesic treatment, in particular for their effects on daily activities such as driving a car. It was demonstrated that chronic pain may significantly impair driving performance. The observed difference in driving performance for chronic pain patients relative to age and education matched healthy controls corresponded to that observed after consuming alcohol up to a blood alcohol concentration of 0.08%, which is above the legal limit for driving a car in most (European) countries. Besides underlying medical or psychiatric conditions, there is now compelling evidence that the use of psychotropic medicinal drugs is an important risk factor for road traffic accidents. This may be particularly relevant for treatment of chronic neuropathic pain in which tricyclic antidepressants, such as amitriptyline, are often prescribed. This drug frequently causes side effects, such as sedation, that may potentially negatively affect daily activities, including driving. In this thesis it was demonstrated that driving performance was significantly impaired after acute dosage of 25 mg nocturnally administered amitriptyline compared to placebo. After two weeks of treatment, no performance deficits were observed anymore, which suggests that tolerance had developed to the impairing side effects of amitriptyline. Further, it was assessed whether patients comply to the advice provided by warning labels affixed to packages of drugs about drugged driving, or continue driving despite this warning. The study results showed that the majority of psychotropic medicinal drug users (71%) reported to drive a car regularly. Warning labels thus seem to have little impact on patients’ decisions whether to drive a car or not. Although the majority (67%) of drivers’ reported to be more careful in traffic while taking drugs, previous studies demonstrated that compensatory strategies, such as reducing speed, are not likely to improve traffic safety, this because of underestimation of traffic hazards and overestimation of own driving skills. Since attentional dysfunction might be an important determinant for driving ability, we tested the hypothesis whether pain patients have deficits in attentional processing capacity by using objective electrophysiological measures. No deficits in attentional capacity were found during either experimentally induced pain in healthy volunteers or in chronic pain patients. However, the results pointed to a deficit in attentional allocation in chronic pain patients. The difficulties in allocating attention to task-relevant stimuli requiring focusing, instead of to competing potentially interfering task-irrelevant stimuli, might explain why driving performance was affected during pain.