Physical Activity Declines over a 12-Month Period in Parkinson's Disease: Considerations for Longitudinal Activity Monitoring.

Purpose: The purpose of this project was to evaluate trends in daily steps in individuals with Parkinson's disease (PD) over a 12-month period using continuous activity monitoring. Environmental (temperature) and cultural factors (represented by day of the week) were evaluated as potential external sources of variability. It was hypothesized that participants daily step counts would decline over the course of 12 months. Further, it was hypothesized that participants would take more steps on warmer days and that the day of the week would have minimal impact on step count as many participants were no longer in the workforce.

Methods: Participants were part of the Usual and Customary Care arm (N = 119) of the CYClical Lower Extremity Exercise Trial for Parkinson's disease - II (CYCLE-II) at the Cleveland Clinic and University of Utah. Participants wore a Garmin Vivofit4® device daily for 12-months. A linear mixed effects model was created to model daily steps over 12-months.

Results: Participants wore their activity monitors 93% of study days. Steps per day declined by 6.1% over 12 months (95% CI 12.6% decline, 0.9% increase, p = 0.09). Steps per day were greater with warmer temperatures (p < 0.001), plateauing and declining around 75-85 degrees Fahrenheit (24-29 degrees Celsius). Participants took fewer steps on Sundays; this difference was more pronounced for Utah participants, who took 25% fewer steps on Sundays compared to other weekdays (p < 0.001).

Conclusions: Most individuals live with PD for decades, and interventions should address the expected decline of 6% in daily step count. Environmental and cultural factors impact daily step count and should be adjusted for in short- and long-term monitoring of physical activity in individuals with PD.