New research out Tuesday looks to pin down the many health problems that can arise from a bout of covid-19. The long list includes more common ailments like pneumonia, kidney failure, and widespread inflammation, as well as rarer complications like serious heart inflammation, collapsed lungs, and severe blood clotting.
The new study, published in the Canadian Medical Association Journal, is the result of collaboration between researchers in Canada and the United States. They looked at de-identified insurance claims data from over 70,000 people in the U.S. who were diagnosed with covid-19 between March 1 and April 30, 2020. This allowed them to compare people’s health after a covid-19 diagnosis to their baseline health pre-covid (to account for chronic conditions unrelated to covid-19, they analysed recent claims made up to a month before their covid-19 diagnosis).
Based on the claims data, the researchers identified 69 diagnosable conditions or symptoms that appeared to be strongly connected to covid-19. Some were plainly expected, as covid-19 is primarily a respiratory illness. Pneumonia (lung inflammation) and respiratory failure were the most widely seen symptoms, for instance. But as other research has suggested, covid-19 can cause other bodily dysfunctions, particularly in people with more serious illness. Kidney failure and sepsis (widespread, life-threatening inflammation) were two other common complications among patients. About half of these people were hospitalized as a result of the viral illness.
The authors also tried to calculate the absolute risk of coming down with any one symptom once you develop symptoms of covid-19. For the most common complications, they estimated that the risk of developing pneumonia was 27.6%, 22.6% for respiratory failure, 11.8% for kidney failure, and 10.4% for sepsis. Other complications were rare overall, but covid-19 appeared to significantly raise their risk of happening. These included myocarditis, or the inflammation of heart muscle, a collapsed lung, and a serious condition called disseminated intravascular coagulation, which is characterised by overactive and widespread blood clotting.
The findings do have their limitations. For one, though this large dataset does include people who weren’t sick enough to need hospitalisation, it still only accounts for patients who sought medical care and were diagnosed with covid-19 in the earliest days of the pandemic. Back then, testing was far more limited, and many people with milder covid-19 were never given the chance to see a doctor. The authors also only chose to study people who filed a medical claim recently before their covid-19 diagnosis (120 to 30 days before the diagnosis), in order to create a clearer comparison between their baseline and post covid-19 health. That likely means that these people were sicker than the general public even before contracting covid-19, the researchers noted. And some milder complications, like a loss of smell or taste, may have not been diagnosed officially as often as they were really happening.
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On the other hand, much of the research trying to figure out the many ways that covid-19 can sicken us has been through small studies or individual case reports, which can’t really tell us anything about how common these complications can be. So at the very least, studies like this can give us a rough outline of the damage that covid-19 is capable of causing. Other research continues to highlight that a substantial chunk of people who contract covid-19 can experience lingering symptoms like brain fog, fatigue, or a loss of smell, even after the initial infection has cleared.
“Understanding the full range of associated conditions can aid in prognosis, guide treatment decisions and better inform patients as to their actual risks for the variety of COVID-19 complications reported in the literature and media,” the authors wrote.
Despite the likely approval of preventative vaccines this month, the pandemic in the U.S. has reached a new record peak, with more than 100,000 Americans currently hospitalized with covid-19, while deaths reported last week were the highest to date.