The role of neuropsychological performance in the relationship between chronic pain and functional physical impairment.

OBJECTIVE: In this study, the relationship between pain intensity, neuropsychological, and physical function in adult chronic pain patients was examined.
DESIGN: Thirty participants with chronic pain completed neuropsychological tests tapping mental processing speed, memory, and executive function. Pain intensity was measured with three visual analog scales and the Pain Rating Index of the McGill Pain Questionnaire. A grip strength test, the 6-minute walk test, the Unipedal Stance Test and the Lifting Low Test were administered in order to obtain a performance-based measure of physical capacity. Self-reported physical ability was assessed with the Disability Rating Index and the Short Form-36 Physical Functioning, and Role Physical scales. Psychosocial function was examined using the Mental Health and Role Emotional subscales of the Short Form-36.
SETTING: The study was set in two outpatient physical therapy clinics in The Netherlands.
RESULTS: The analysis showed that a lower mental processing speed was related to a higher level of pain, as well as to a lower performance-based and self-reported physical functioning. In addition, both performance-based and self-reported physical function revealed an inverse correlation with pain intensity. Psychosocial function turned out to be an important mediator of the relationship between pain and self-reported, but not performance-based, physical function. Mental processing speed, on the other hand, was found to mediate the relationship between pain and performance-based physical functioning.
CONCLUSION: The results suggest that in chronic pain patients, mental processing speed mediates the relationship between pain and physical function. Wiley Periodicals, Inc.