Comparing GPS-based community mobility measures with self-report assessments in older adults with Parkinson’s disease

BACKGROUND: Real-life community mobility measures for older adults, especially those with Parkinson's disease, are important tools when helping individuals maintain optimal function and quality of life. This is one of the first studies to compare an objective GPS sensor and subjective self-report community mobility measures in an older clinical population. METHODS: Over 14 days, 54 people in Ontario, Canada with early to mid-stage Parkinson's Disease (mean age = 67.5 +/- 6.3 years; 47 men; 46 retired) wore a wireless inertial measurement unit with GPS (WIMU-GPS), and completed the Life Space Assessment and mobility diaries. We assessed the convergent validity, reliability and agreement on mobility outcomes using Spearman's correlation, intraclass correlation coefficient and Bland-Altman analyses, respectively. RESULTS: Convergent validity was attained by the WIMU-GPS for trip frequency (rs = 0.69, 95% CI = 0.52 to 0.81) and duration outside (rs = 0.43, 95% CI = 0.18 to 0.62), but not for life space size (rs = 0.39, 95% CI = 0.14 to 0.60). The Life Space Assessment exhibited floor and ceiling effects. Moderate agreements were observed between WIMU-GPS and diary for trip frequency and duration (intraclass correlation coefficients = 0.71, 95% CI = 0.51 to 0.82; 0.67, 95% CI = 0.42 to 0.82, respectively). Disagreement was more common among non-retired individuals. CONCLUSIONS: WIMU-GPS could replace diaries for trip frequency and duration assessments in older adults with Parkinson's Disease. Both assessments are best used for retired persons. However, the Life Space Assessment may not reflect actual mobility.