The relationships between three-axis accelerometer measures of physical activity and motor symptoms in patients with...

Various wearable devices for objectively evaluating motor symptoms of patients with Parkinson's disease (PD) have been developed. Importantly, previous studies have suggested protective effects of physical activity in PD. However, the relationships between conventional clinical ratings for PD and three-axis accelerometer measures of physical activity (e.g., daily physical activity levels [PAL] or metabolic equivalents of task [METs]) are still unclear, particularly for METs. In the current study, we sought to elucidate these relationships on a daily basis, and to clarify optimal predictors for clinical states on a 30-min basis.

Patients who were hospitalized for adjustment of drugs or deep brain stimulation were enrolled. Using waist-worn three-axis accelerometers, PAL and METs parameter data were obtained and compared with UPDRS-3[On] and symptom diary data. We extracted data from the patients' best and worst days, defined by the best and worst UPDRS-3[On] scores, respectively. Thus, 22 data sets from 11 patients were extracted. We examined the correlations and produced scatter plots to represent the relationships, then investigated which METs parameters and activity patterns were the best predictors for "On" and "dyskinesia".

The parameter "mean METs value within the 95-92.5 percentile range on a day (95-92.5 percentile value)" exhibited the strongest correlation with conventional daily clinical ratings (Rho: - 0.799 for UPDRS-3[On], 0.803 for On hours [p < 0.001]). Scatter plots suggested that PAL tended to have higher values in patients with involuntary movement. However, METs parameters focusing on higher METs seemed to alleviate this tendency. We clarified that "time over 2.0 METs" and "time over 1.5 METs" could be predictors for "On" and "dyskinesia" on a 30-min basis, respectively (AUROC: 0.779 and 0.959, 95% CI: 0.733-0.824 and 0.918-1.000). The specificity and sensitivity of the optimal activity pattern for "On" were 0.858 and 0.621.

This study suggested feasible activity patterns and METs parameters for objective evaluation of motor symptoms on a 30-min or daily basis. Three-axis accelerometer measures focusing on higher METs may be appropriate for evaluating physical activity. Further larger-scale studies are necessary to clarify the validity, reliability, and clinical utility of these objective measures.