How researchers track Long COVID’s impacts

The Census and CDC’s Household Pulse Survey provides one major source of data on Long COVID prevalence.

I got an interesting question from a reader last weekend, asking if excess deaths might be one way to identify the impact of Long COVID. It’s an interesting idea: could the numbers of deaths from medical causes above what researchers expect in a given timeframe indicate some premature deaths tied to Long COVID?

Based on my previous work with excess deaths (see MuckRock’s Uncounted project), I think this could be possible, though it’d likely be very hard to identify direct relationships between Long COVID and specific deaths. As far as I know, no researchers are working on this question; if you know of anyone who is, please reach out.

Still, the reader’s question got me thinking about how, exactly, we track the impacts of Long COVID. Doctors, researchers, and long-haulers themselves have learned a lot about the condition over the last three years. We still don’t have clear estimates of exactly how many people in the U.S. are dealing with this chronic disease, but we’ve come much closer to understanding its impacts than we were when patients first began advocating for themselves in 2020.

Tracking Long COVID is challenging because of uneven access to COVID-19 tests and to medical care, which means long-haulers with certain types of privilege are more likely to get an accurate diagnosis. A lack of knowledge about Long COVID, both among medical professionals and among the overall population of people who might get it, also contributes to this issue. (For more details, see this post from early December.)

Still, some strategies have emerged for identifying people with Long COVID and tracking how the condition is impacting them. Here are a few.

Following people who were hospitalized for COVID-19:

In this strategy, researchers identify people who had COVID-19 and track how the virus impacts them over time. It’s often easiest for researchers to track people who were hospitalized, since hospitals keep detailed medical records of their patients, though this tactic leaves out long-haulers who initially had mild cases.

Sometimes, researchers doing this type of follow-up study will directly survey COVID-19 patients, which can lead to more comprehensive data than using health records alone. One recent study in this category found that, among a group of 800 adults hospitalized for COVID-19, about half were still experiencing some financial issues and limitations in their ability to do day-to-day activities six months later. The study’s authors noted that financial issues were “reported more frequently” among patients who identified with demographic minorities.

Following COVID-positive patients through electronic health records:

In other studies, researchers use electronic health records to identify how people who had COVID-19 fare months later. Two recent studies associated with the National Institutes of Health’s RECOVER initiative fall into this category. One paper utilized records from New York City health centers, and found that Black and Hispanic adults were more likely to have potentially Long COVID-related health issues following a COVID-19 case. The other paper, which used records from 34 medical centers across the U.S., found that white, female, non-Hispanic patients living in areas with greater healthcare access were more likely to receive an actual Long COVID diagnosis.

Angela Vázquez, president of the Long COVID group Body Politic, summarized the two new studies succinctly on Twitter, writing: “Black and Hispanic Americans appear to experience more symptoms and health problems related to #LongCovid than white people, but are not as likely to be diagnosed with the condition.” Vázquez also pointed out that the studies may have missed neurological symptoms among Black and Hispanic patients, due to less access to care for these groups.

Broad surveys of potential patients:

Electronic health records are far from perfect sources of Long COVID data, as they often present only sets of information that doctors are already compiling—and they are often biased towards the people who are able to access medical care for COVID-19 (or Long COVID) in the first place. As a result, some researchers track Long COVID through broader surveys, seeking to identify everyone who might have some long-term symptoms following a COVID-19 case, even if those people might not be calling their condition “Long COVID.”

The Census and CDC’s Household Pulse Survey questions on Long COVID are one notable example of this strategy. Census researchers ask a random sample of Americans whether they’ve had “any symptoms lasting 3 months or longer” following a COVID-19 case, then follow up with questions about whether those symptoms are current and whether they impact the respondent’s ability to carry out day-to-day activities. The resulting data provide a broader view of Long COVID in the U.S., including people who may not have sought medical care for their symptoms.

Biological studies of specific organs impacted by COVID-19:

In order to better understand how a case of COVID-19 may lead to long-term, debilitating symptoms, some researchers focus on studying exactly what happens to different parts of the body after a coronavirus infection. This research sometimes focuses on testing for the continued presence of virus after a patient’s acute COVID-19 case is over or tracking changes to the immune system, as scientists test different theories into how Long COVID occurs.

One major area of research has been the brain. Freelance journalist Stephani Sutherland recently published a major feature in Scientific American exploring how Long COVID impacts the brain and nervous system, summarizing research into the biological causes of common symptoms like fatigue and brain fog. Physician E. Wesley Ely, who cares for Long COVID patients, wrote an essay on the same topic that appeared in STAT News this week; Ely discussed what he’s learned from autopsy studies examining the brains of people who had COVID-19.

Identifying trends in the labor market:

Finally, researchers often seek to track the impacts of Long COVID indirectly, by looking at statistics on people who have left the labor market during recent years. It’s no secret that a lot of people have left their jobs during the pandemic; Long COVID experts argue that the chronic disease may be one major driver of the labor shortage. One often-cited Brookings Institution analysis suggested two to four million people may be out of work due to Long COVID.

This strategy for studying Long COVID may be the most difficult, as it’s hard to actually tie job loss numbers to the condition without more specific data. Most research surveys or electronic health records databases don’t ask people about their work situations; the recent study cited above is a notable outlier. Similarly, most unemployment claims and short-term disability datasets don’t ask people if Long COVID is contributing to their need for assistance.

Still, I hope to see more studies in the future that examine Long COVID’s impact on work and other activities. Related: the U.S. Department of Labor recently published a report about the need for more assistance geared toward workers with Long COVID.

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