Perceived control is a concurrent predictor of activity limitations in patients with chronic idiopathic axonal polyneuropathy

Objectives: To investigate (1) whether control perceptions (person's perception of ease or difficulty of performing behavior) and emotions contribute to activity limitations and if so (2) whether these variables mediate the relation between impairment and activity limitations in patients with chronic idiopathic axonal polyneuropathy (CIAP).

Design: Cross-sectional study.

Setting: Outpatient clinics of a university medical center.

Participants: Fifty-six patients diagnosed with CIAP.

Interventions: Not applicable.

Main Outcome Measures: Control perceptions about performing activities (questionnaire based on the theory of planned behavior), emotions (Hospital Anxiety and Depression Scale), activity limitations (performance: Shuttle Walk Test [SWT]; self-report: Medical Outcomes Study 36-Item Short-Form Health Survey [SF-36] physical functioning subscale, self-reported ability to walk), and physical impairments (muscle strength, sensory function).

Results: Control perceptions significantly (P <.01) correlated with all measures of activity limitations (r range,.58-.69). Hierarchical multiple regression analyses showed that perceived control explained 9% of the variance in the SWT (beta=34, P <.01), 12% in the SF-36 (beta=.40, P <.01), and 24% in ability to walk (beta=.54, P <.01). In all measures of activity limitations, perceived control significantly mediated the effect of impairment.

Conclusions: Perceived control explained and mediated variance in activity limitations, whereas emotions did not. This suggests that increasing patients' perceptions of control might enhance performance of activities, even without changes in impairment.