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Predicting ‘Long COVID Syndrome’ with Help of a Smartphone App

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Zoe COVID Sympton Study Tracker app
Credit: Zoe Global

As devastating as this pandemic has been, it’s truly inspiring to see the many innovative ways in which researchers around the world have enlisted the help of everyday citizens to beat COVID-19. An intriguing example is the COVID Symptom Study’s smartphone-based app, which already has been downloaded millions of times, mostly in the United States and United Kingdom. Analyzing data from 2.6 million app users, researchers published a paper last summer showing that self-reported symptoms can help to predict infection with SARS-CoV-2, the coronavirus that causes COVID-19 [1].

New work from the COVID Symptom Study now takes advantage of the smartphone app to shed more light on Long COVID Syndrome [2], in which people experience a constellation of symptoms long past the time that they’ve recovered from the initial stages of COVID-19 illness. Such symptoms, which can include fatigue, shortness of breath, “brain fog,” sleep disorders, fevers, gastrointestinal symptoms, anxiety, and depression, can persist for months and can range from mild to incapacitating

This latest findings, published in the journal Nature Medicine, come from a team led by Claire Steves and Tim Spector, King’s College London, and their colleagues, and that includes NIH grantee Andrew Chan, Massachusetts General Hospital, Boston, and others supported by the Massachusetts Consortium on Pathogen Readiness. The team began by looking at data recorded between March 24-Sept. 2, 2020 from about 4.2 million app users with an average age of 45, about 90 percent of whom lived in the U.K., with smaller numbers from the U.S. and Sweden.

For this particular study, the researchers decided to focused on 4,182 app users, all with confirmed COVID-19, who had consistently logged in their symptoms. Because these individuals also started using the app when they still felt physically well, the researchers could assess their COVID-19-associated symptoms over the course of the illness.

While most people who developed COVID-19 were back to normal in less than two weeks, the data suggest that one in 20 people with COVID-19 are likely to suffer symptoms of Long COVID that persist for eight weeks or more. About one in 50 people continued to have symptoms for 12 weeks or more. That suggests Long COVID could potentially affect many hundreds of thousands of people in the U.K. alone and millions more worldwide.

The team found that the individuals most likely to develop Long COVID were older people, women, and especially those who experienced five or more symptoms. The nature and order of symptoms, which included fatigue, headache, shortness of breath, and loss of smell, didn’t matter. People with asthma also were more likely to develop long-lasting symptoms, although the study found no clear links to any other pre-existing health conditions.

Using this information, the researchers developed a model to predict which individuals were most likely to develop Long COVID. Remarkably, this simple algorithm—based on age, gender, and number of early symptoms–accurately predicted almost 70 percent of cases of Long COVID. It was also about 70 percent effective in avoiding false alarms.

The team also validated the algorithm’s predictive ability in data from an independent group of 2,472 people with confirmed COVID-19 and a range of symptoms. In this group, having more than five symptoms within the first week also proved to be the strongest predictor of Long COVID. And, again, the model worked quite well in identifying those most likely to develop Long COVID.

These findings come as yet another important reminder of the profound impact of the COVID-19 pandemic on public health. This includes not only people who are hospitalized with severe COVID-19 but, all too often, those who get through the initial period of infection relatively unscathed.

Recently, NIH announced a $1.15 billion investment to identify the causes of Long COVID, to develop ways of treating individuals who don’t fully recover, and, ultimately, to prevent the disorder. We’ve been working diligently in recent weeks to identify the most pressing questions and areas of greatest opportunity to address this growing public health threat. As a first step, NIH is funding an effort to track the recovery paths of at least 40,000 adults and children infected with SARS-CoV-2, to learn more about who develops long-term effects and who doesn’t. If you’d like to find a way to pitch in and help, getting involved in the COVID Symptom Study is as easy as downloading the app.


[1] Real-time tracking of self-reported symptoms to predict potential COVID-19. Menni C, Valdes AM, Freidin MB, Sudre CH, Nguyen LH, Drew DA, Ganesh S, Varsavsky T, Cardoso MJ, El-Sayed Moustafa JS, Visconti A, Hysi P, Bowyer RCE, Mangino M, Falchi M, Wolf J, Ourselin S, Chan AT, Steves CJ, Spector TD. Nat Med. 2020 Jul;26(7):1037-1040. doi: 10.1038/s41591-020-0916-2. Epub 2020 May 11.

[2] Attributes and predictors of long COVID. Sudre CH, Murray B, Varsavsky T, Graham MS, Penfold RS, Bowyer RC, Pujol JC, Klaser K, Antonelli M, Canas LS, Molteni E, Modat M, Jorge Cardoso M, May A, Ganesh S, Davies R, Nguyen LH, Drew DA, Astley CM, Joshi AD, Merino J, Tsereteli N, Fall T, Gomez MF, Duncan EL, Menni C, Williams FMK, Franks PW, Chan AT, Wolf J, Ourselin S, Spector T, Steves CJ. Nat Med. 2021 Mar 10.


NIH launches new initiative to study to “Long COVID”. 2021 Feb 23. (NIH)

COVID-19 Research (NIH)

Massachusetts Consortium on Pathogen Readiness (Boston)

COVID Symptom Study

Claire Steves (King’s College London, United Kingdom)

Tim Spector (King’s College London)

Andrew Chan (Massachusetts General Hospital, Boston)

NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases


  • carolyn j zoller says:

    be nice if we could get our shots havent had the first one yet 72years old 2 underlying problems nothing places are too far of the places here in pittsfield ma are always booked

    • Pat Moore says:

      I had 2 doses Moderna and boosted.2nd Moderna shot. Had reaction next day. Know how when you’ve had a hip act up, sciatica or arthritis flare up? Well imagine 10 times pain factor. Took ibuprofen and it went away day later. Maybe first shot only tickled my immune system while 2nd WOKE it up. High risk. Type 2 diabetes, lung issues from bronchitis and sleep apnea. Glad I got vaccinated always wear K95 mask outside of home.

  • Yvonne howard says:

    I have had a large loss of hair..I had covid in left me with acute heart failure tachycardia and a leaky valve..its been almost 4 months…I don’t know what else is going to happen..a new symptom could arise tomorrow. who knows?

  • Judith M. says:

    My 36-yr-old, formerly healthy daughter got COVID-19 in mid-March 2020. As of today, 3/23/2021, she is still ill with long COVID. All blogs from Dr. Collins that I have seen on this topic describe long COVID cases as lasting 3 months or more. I have read elsewhere that many such cases have lasted, like my daughter’s, as long as a year and still ongoing. I hope he knows that and, if so, will change what he writes. The Moderna vaccine has reduced her symptoms but she remains disabled.

  • Pat A Parker says:

    COVID Symptom Study is as easy as downloading the app, you are assuming everyone has this type of phone, would like to help but I do not have this phone,

    • Brinda B. says:

      77 y.o. female, 2nd Pzier shot Feb 16th followed by massive inflammatory response in hands and wrists, did not take an Aleve until day 10 post injection to allow vaccine to work its magic and had stopped taking my usual bedtime 220mg. 4 days before I went for the 2nd shot // 2/12/21 Have had many vaccines over my lifetime without any side effects. Hx of global travel, with Red cross and military. Career as ICU RN. Exposure to NTM chimerea with open heart surgery for MVR , no symptoms………………I find it all very interesting.

    • Lorraine Alice Calderon says:

      Time to get a new phone.

  • Robert says:

    I have sleeping disorders. I would like it if this could finish someday. My wife is very anxious and I am very stressed everyday about my kids

  • Norberto G. says:

    I am a male, 66 years old. Haven’t had Covid-19. Received my Pfizer first shot Saturday March 27. No secondary symptoms. Little pain in my left arm at the spot where they inserted the needle.

  • Barry S. says:

    Had my Pfizer 1st jab Mar 2, 2021, and 2nd jab Mar 24, 2021. No ill affects after the 1st jab, but interestingly enough, 24 hrs after the 2nd jab I felt fatigued, slight back aches, overall feeling of contracting Flu-like symptoms, so went to bed early. Next morning was back to 100%, feeling normal. I now anticipate that after two more weeks I’ll have the 95% protection and will feel safer. Thank y’all for dealing with this nasty worldwide pandemic.

  • Susan M. says:

    I had a reaction to the MMR vaccine many years ago. It happened as per the flyer,, nine days after injection. I have numerous sensitivities to all medications and reactions quite frequently. Two years ago, I had a sudden onset of angioedema, etiology unknown. Saw an allergist – she gave me an epipen to use as needed. I am very nervous to get the vaccine. What would you recommend? My pcp is reluctant to give full approval as who can say what will happen. I am 73 years old.

    • Lorraine Alice Calderon says:

      There’s no solid evidence that every illness you’ve had is related to that previous vaccine. You really don’t want Covid at 73 or at any age really, and I doubt you want to live the rest of your life as a recluse, because you don’t want to catch Covid. Those are your choices without the vaccine. If you come out of isolation, you’re taking a big risk. If I were in your shoes I’d get the vaccine. I’m more petrified of what Covid can do to me than I am of anything that the vaccine can do to me.

  • Candace S. says:

    I am highly allergic to MSG (neurotoxicity). No covid, received Pfizer vaccine numbers one and two. Absolutely no untoward effects.
    I have been part of the Harvard Nurses Health Study for > 30 years.

  • Lisa K. says:

    Had my both my shots, nothing was wrong, still being safe, wearing mask, no big gatherings, sanitizing more now,. Thank God daily for his grace & mercy.

  • Irma G says:

    My whole LONG CoVd has been a nightmare! Late March 2020 to now (ongoing). Latest symptoms are CoVd toes and brittle nails. I have had beautiful strong nails all my life. Now one breaks every day. Over nothing. Initially, since I could breathe, no testing until months later. I developed no antibodies but am genetically immunosuppressed so no surprise there. Thinking about flying to India to get the killed virus vaccine since no one in our first world countries want to make it available to us

  • LC says:

    I am only 53, but I have very very bad Asthma. I already struggle with breathing and when I get a cold or flu, my Asthma gets so bad that I have to be hospitalized. If I ever got Covid, I would be in big trouble. I probably wouldn’t survive it. I’ve been avoiding everyone but my boyfriend who I live with, since the pandemic started. I’m very careful and I avoid leaving our apartment as much as possible. I keep busy being a full time student. If I have to go somewhere I wear my mask and try to avoid being inside, or in small spaces, with people for longer than 10 minutes. I try to keep my distance as well. I live in California, which Unfortunately is in the stupid idiotic United States, so I am not eligible for the vaccine yet. You would think that someone high risk would be eligible. I’m not careless, like everyone else, behaving as if the pandemic is over, so hopefully my good behavior will continue to pay off until I m fully vaccinated. Even then, I plan to continue wearing a mask and being extremely selective and careful. Thank you so much for letting me be a part of this study. Best wishes to you all and please stay safe!

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