A new app could help people with long covid cope with their condition by giving them a clearer understanding of what helps—and hinders—their health.

People with long covid, defined by the World Health Organization as a post-covid illness lasting two months or more, suffer from symptoms that include headaches, fatigue, weakness, and fever. Some use a practice called pacing, where they balance activity with periods of rest to recover, to keep things under control. If they exert themselves too hard, it can make things worse.

The new app, called Visible, aims to help people manage that process by collecting data every day in order to understand how their symptoms fluctuate. Users measure their heart rate variability (the variation in time between beats) every morning by placing a finger over the phone’s camera for 60 seconds. This measures the pulse by recording small changes in the color of the user’s skin.

The user then rates the severity of their long covid symptoms in the evening on a scale of 0 to 3 (0 representing no symptoms, and 3 representing severe symptoms). Research from the American Heart Association has found that reduced heart rate variability, which corresponds with a more stressed nervous system, is common in people with long covid. 

Tracking heart rate variability makes it easier to predict when someone is likely to become fatigued. Visible uses this data to create a “pace score” of 1 to 10 (8-10 indicating good recent pacing, 4-6 suggesting it would be wise to factor in a quiet next few days, and 1-3 meaning the person should prioritize rest) to help users decide when to take it easy. 

Visible’s co-creator, Harry Leeming, who has been living with long covid since September 2020, hopes that it will help both users and the wider society gain a better understanding of the condition, which medical experts still know surprisingly little about. Users will soon be able to opt to share their data with researchers at Imperial College London, the company says. 

Visible is just one of a range of projects designed to help people with long covid. Researchers from University College London have recently created an app called Lungy, which is designed to help users with long covid, asthma, or chronic obstructive pulmonary disease (COPD) do breathing exercises. Another app, from the UK’s Northern Care Alliance NHS Group, has been developed to help patients log their progress so that clinicians can adjust their treatment accordingly.

Behind the numbers, there is an enormous amount of individual pain, misery, and frustration regarding medical ignorance about the condition, says Mike Clarke, a 44-year-old medical copywriter in Bristol, UK, who has been living with long covid since October 2020. He has to spend hours every day lying down because even just sitting up puts strain on his heart.

“I had a couple of particularly bad health days, and my score [on the app] the next day was appropriately low. It may not seem like much, but after two years of doctors telling me all medical tests showed that everything in my body was fine, I’ve felt more validated by the data from Visible in a week and half of use,” he says.

“After two years with absolutely no progress, most people like me with long covid are desperate for someone or something—anything—to offer hope. To me, the Visible app provides me little glimpses of that.”