Wearable activity monitors could be useful in assessing the health of cancer patients and making predictions about mortality and adverse events, according to a study published last week in Nature's Digital Medicine partner journal.

"An objective evaluation of patient performance status (PS) is difficult because patients spend the majority of their time outside of the clinic, self-report to providers, and undergo dynamic changes throughout their treatment experience," researchers wrote. "Real-time, objective activity data may allow for a more accurate assessment of PS and physical function, while reducing the subjectivity and bias associated with current assessments."

In the study, 37 patients wore the Fitbit Charge HR to track activity, heart rate, and sleep. Researchers tracked their step counts as well as standard measures of performance status, the ECOG and Karnofsky provider assessments, and the patient-reported NIH PROMIS assessment. They then looked for correlations between the step data, the traditional performance assessments, and outcomes including all-cause mortality, hospitalizations, and adverse events.

Researchers found that an increase of 1,000 steps per day, on average, was associated with significantly lower odds of hospitalizations, fewer serious adverse events, and increased survival. They also found that step counts correlated with assessment scores — patients who walked more scored higher on the assessments, and those who walked less scored worse.

The study was a small feasibility study; researchers suggested that a larger, randomized trial is the next step. But the findings are still promising for this use case for wearables.

"While our results cannot definitively determine whether activity monitor data can replace ECOG-PS or KPS assessments, they do support their use as a supplement of current functionality tools," they wrote. "Not only were step counts and other activity metrics correlated with performance status, but they also provided a more detailed and continuous account of the patients’ activity levels with the additional benefit of being recorded in the patients’ free-living environments. Their use could also minimize recall biases while removing burden associated with completing multiple surveys and questionnaires in clinic."