Wearable sensors measure how much light, moderate or vigorous physical activity people had during the day, how much time they spent sitting or inactive, and their circadian rhythms, or sleep-wake patterns.

“Timely identification of patients at risk for disease progression is essential to reduce long-term disability, but the current tests for measuring MS disability are not designed to detect small changes,” said study author Kathryn C. Fitzgerald, ScD, ScM, of Johns Hopkins University in Baltimore, Maryland. “Using a relatively inexpensive and accessible device around the wrist may help us identify early changes in the disease.”