Characterization of ILI Burden Using Wearable Sensor Measures: Steps
SE, ILI
EVENTS, EVENT, INFLUENZA-LIKE ILLNESS, INFLUENZA
Across the study period, the ILI population took an average of 8019 daily steps and spent 15% of the nonresting portion of their day active with >50 steps per minute (out of all the minutes with nonzero steps), which is hereafter referred to as active time.Participants saw a change in their total daily steps during ILI events. Just before ILI onset, daily step counts began decreasing from baseline values, with a peak change observed on day 0 (day of symptom onset), when participants lost a mean of 2516 daily steps (Deviations from baseline levels across wearable measures during an influenza-like illness (ILI) event. Day-by-day group mean (SE) changes from baseline values for 5 wearable sensor features derived from day-level sensor data are shown. “Steps total” was the total number of steps taken per day. “Total steps count” was the total number of steps taken per day. “Proportion of steps taken with >50 spm” was the ratio of minutes in the day that the participant took over 50 steps per minute (spm) relative to the total number of minutes with at least 1 step. “Sleep duration” was the total number of minutes in the day that the participant spent asleep. “Sleep efficiency” was the ratio of minutes the participant was asleep relative to the total minutes spent in bed until the end of the main sleep event (obtained from the Fitbit application programming interface). “RHR” was heart rate (beats per minute [bpm]) during periods of inactivity (obtained from the Fitbit application programming interface). Gray lines illustrate values for the entire wearable analysis population available for that wearable sensor feature; colored lines represent values for the subset of the analysis population who tested positive for influenza. The shaded region covers days −4 to +9 relative to ILI onset, which was the time window used in statistical analyses of day-by-day ILI burden. Influenza+: influenza-positive; RHR: resting heart rate.Active time also decreased from baseline values during ILI events. Across the ILI population, the peak mean change in active time was −4% of the total daily minutes, which was observed on days 0 and 1 (