Test-retest reliability of physical activity questionnaires in Parkinson’s disease

BACKGROUND: People with Parkinson’s disease are less physically active than controls. It is important to promote physical activity, which can be assessed using different methods. Subjective measures include physical activity questionnaires, which are easy and cheap to administer in clinical practice. Knowledge of the psychometric properties of physical activity questionnaires for people with Parkinson’s disease is limited. The aim of this study was to evaluate the test-retest reliability of physical activity questionnaires in individuals with Parkinson’s disease without cognitive impairment. METHODS: Forty-nine individuals with Parkinson’s disease without cognitive impairment participated in a test-retest reliability study. At two outpatient visits 8 days apart, the participants completed comprehensive questionnaires and single-item questions: International Physical Activity Questionnaire-Short Form (IPAQ-SF), Physical Activity Scale for the Elderly (PASE), Saltin-Grimby Physical Activity Level Scale (SGPALS) and Health on Equal Terms (HOET). Test-retest reliability was evaluated using the intraclass correlation coefficient (ICC), standard error of measurement (SEM), limits of agreement, weighted kappa or the Svensson method. RESULTS: Several of the physical activity questionnaires had relatively low test-retest reliability, including the comprehensive questionnaires (IPAQ-SF and PASE). Total physical activity according to IPAQ-SF had an ICC value of 0.46 (95% confidence interval [CI], 0.21–0.66) and SEM was 2891 MET-min/week. The PASE total score had an ICC value of 0.66 (95% CI, 0.46–0.79), whereas the SEM was 30 points. The single-item scales of SGPALS-past six months (SGPALS-6 m) and HOET question 1 (HOET-q1) with longer time frames (6 or 12 months, respectively) showed better results. Weighted kappa values were 0.64 (95% CI, 0.45–0.83) for SGPALS-6 m and 0.60 (95% CI, 0.39–0.80) for HOET-q1, whereas the single-item questions with a shorter recall period had kappa values < 0.40. CONCLUSIONS: Single-item questions with a longer time frame (6 or 12 months) for physical activity were shown to be more reliable than multi-item questionnaires such as the IPAQ-SF and PASE in individuals with Parkinson’s disease without cognitive impairments. There is a need to develop a core outcome set to measure physical activity in people with Parkinson’s disease, and there might be a need to develop new physical activity questionnaires.