Study design: A controlled study with a 6-month follow-up period.
Objectives: To find an explanation for the association between impairment in information processing, i.e., slow reaction times, and chronic low back trouble.
Summary of background data: Low back trouble, chronic pain in general, and depression have been associated with impaired cognitive functions and slow reaction times. It is a common phenomenon that the preferred hand performs better than the nonpreferred hand in motor tasks. The authors hypothesized that chronic low back trouble hampers the functioning of short-term memory in a way that leads the preferred hand to loose its advantage over the nonpreferred hand, but that the advantage would be restored during the rehabilitation.
Methods: Sixty-one healthy control subjects and 68 patients with low back trouble participated in the study. Reaction times for the preferred and nonpreferred upper limbs were tested. A multiway analysis of covariance was used to examine the group, handedness, and rehabilitation effects on reaction times. The hypothesis was specifically tested with a third-degree interaction: group-handedness-rehabilitation.
Results: A significant interaction among group, handedness, and rehabilitation was found (P = 0.05). At the beginning, the reaction times for the preferred hand were faster among the control subjects (P = 0.001), but not among the patients with low back trouble (P = 0.62). After the rehabilitation, the preferred hand was faster both among the control subjects (P = 0.001) and the patients with low back trouble (P = 0.0002). During the rehabilitation, back pain, psychological distress, and general disability decreased significantly among the patients with chronic low back trouble.
Conclusions: The results support the hypothesis that chronic low back trouble (i.e., pain, psychological distress, and general disability) hampers the functioning of short-term memory, which results in decreased speed of information processing among patients with chronic low back trouble.