Gait velocity has been consistently shown to be an important indicator and predictor of health status, especially in elderly populations. Gait velocity is often assessed clinically, but clinical assessments occur infrequently and thus do not allow optimal detection of key health changes when they occur. In this paper, we propose using the time it takes a person to move between rooms in their home - referred to as 'transition times' - estimated from passive infrared motion sensors installed in a patients own home to predict gait velocity. By using a support vector regression approach to model the relationship between transition times and observed gait velocities , we show that we can predict unobserved velocities accurately. In particular, we demonstrate that the proposed approach has an average error of 4 cm/sec using data collected over a 5 year period from 76 study participants monitored both in their own homes and within a clinical setting. The proposed method is simple and cost effective , and has advantages over competing approaches such as not requiring patients to wear a device or needing dedicated sensors to measure gait . Furthermore, this method provides substantially more frequent estimates of gait velocity than are provided by other approaches .
Gait velocity has been consistently shown to be an important indicator and predictor of health status, especially in older adults. It is often assessed clinically, but the assessments occur infrequently and do not allow optimal detection of key health changes when they occur. In this paper, we show that the time gap between activations of a pair of Passive Infrared (PIR) motion sensors installed in the consecutively visited room pair carry rich latent information about a person's gait velocity. We name this time gap transition time and show that despite a six second refractory period of the PIR sensors, transition time can be used to obtain an accurate representation of gait velocity. Using a Support Vector Regression (SVR) approach to model the relationship between transition time and gait velocity , we show that gait velocity can be estimated with an average error less than 2.5 cm/sec . This is demonstrated with data collected over a 5 year period from 74 older adults monitored in their own homes . This method is simple and cost effective and has advantages over competing approaches such as : obtaining 20 to 100x more gait velocity measurements per day and offering the fusion of location-specific information with time stamped gait estimates. These advantages allow stable estimates of gait parameters (maximum or average speed, variability) at shorter time scales than current approaches. This also provides a pervasive in-home method for context-aware gait velocity sensing that allows for monitoring of gait trajectories in space and time .
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