Remote timed up and go evaluation from activities of daily living reveals changing mobility after surgery.

BACKGROUND: Mobility impairment is common in older adults and influences negatively the quality of life. Mobility may changes rapidly following hospital discharge. The Timed Up and Go test (TUG) is often used to assess functional mobility; however, because TUG may require supervision from a trained clinician, assessments may be infrequent. 
 Objective. In this paper, we aim at providing a method to evaluate TUG remotely from activities in free-living, enabling continuous remote mobility monitoring without expert supervision. The method is used to monitor changes in mobility following Total Hip Arthroplasty (THA).
 Methods. 239 older participants (aged 65-91 years) performed a standardized TUG in a laboratory and wore a wearable pendant device that recorded activities of daily living (ADLs, including walks and sit-to-stand transitions) for at least 3-days. ADLs from were extracted from continuously recorded sensor data and used to develop a regularized linear model for remote TUG test estimation. Changes in the remote TUG were then evaluated for 12-weeks in 15 patients (aged 18-70 years) during rehabilitation following hospital discharge after Total Hip Arthroplasty (THA).
 Results. In leave-one-out-cross-validation, a strong correlation (r=0.70) was observed between the new remote TUG and actual TUG times. Test-retest reliability of 3 day estimates was high (ICC=0.94). Compared to 2-weeks post-THA, remote TUG was significantly improved at 6-weeks (11.7±3.9 s vs 8.0±1.8 s, p<0.001), with no further change at 12-weeks (8.1±3.9 s, p=0.37).
 Conclusions. Our results show that remote TUG can be estimated in older adults using 3-days of ADL data. Remote TUG has discriminatory potential for identifying frail elderly and may provide a convenient way to remotely monitor changes in mobility in unsupervised settings.&#13.