The EconomistThe Economist

Some health apps are able not just to diagnose diseases, but also to treat them

07 May 2022 · 9 min read

“IT LOOKS LIKE your back is a bit tight today. Let’s modify your workout.” The voice is gentle yet commanding, the instructions rolled out in the signature cadence of a physiotherapist. It is also unmistakably robotic. The AI physio issues her commands straight from a smartphone’s speakers. A phone with a camera is all she needs to do her job: select the exercises to suit the patient’s injury, guide him through each session and order corrections when he is not doing something right (bending a knee at the wrong angle, for example). An AI algorithm marks up his body as he moves, which is how it knows when a joint is hurting or the back is stiffer than the day before.

This digital therapist, developed by Kaia Health, a German startup, is, by many measures, as good as a human therapist. One trial, which involved 552 exercises by osteoarthritis patients, found that human therapists agreed with the corrections to exercise suggested by Kaia’s app as often as they agreed with the corrections suggested by other human therapists. In clinical trials patients with back pain using the app improved more than those who got in-person physiotherapy. Making people with injuries bend and twist carries some risks. On that, too, Kaia’s app is no worse than human experts. Less than 0.1% of nearly 140,000 users of the app in studies reported adverse events.

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