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Long Covid estimates are shockingly high. That’s how you understand them

TThink of the Adults You Know: 1 in 5 Has Long Covid, CDC Estimates?

Asking this question should in no way diminish the suffering of people who thought they were done with their infections, only to find their return to well-being is still out of reach. But knowing how many people are living with this bitter legacy of Covid-19, and which of the working-age adults are unable to work or care for their families, is critical to their care and the health of our society.

It’s important to remember that Long Covid is an evolving umbrella term for a range of symptoms that vary in both number and degree. Some housebound people experience a brain fog that completely robs them of concentration, while others find that reminders help them get through their workday. Some ex-athletes can’t complete a 6-minute walk test, while others can gradually regain activity if they monitor their heart rate. Long Covid clinics, adapting techniques from rehabilitation medicine, see people eventually get better. In a world transitioning away from busy inner cities to a hybrid work-from-home status, we might not see who’s missing.


However long the toll of Covid lasts, there will be too many people. However you collect or analyze the data, experts told STAT, the proportion of people whose annoying, sometimes disabling symptoms persist after their acute Covid-19 infection is significant and worrying. It’s the cruelty of big numbers: even if the actual prevalence of long Covid is much lower than recent estimates, a small percentage of a big number is a big number.

And yet the US has been operating almost normally for months. What could explain this discrepancy between estimates and general experience? It’s eerily similar to the early days of the pandemic, when people asked each other if they knew anyone who had contracted the coronavirus, followed by the downside more than two years later: knowing few people who didn’t were, and no one who did. not been exposed.


Here are some factors to help understand the current range of estimates.

First, what are the numbers?

That 20% number, from a recent CDC analysis of millions of medical records, implies that tens of millions of Americans — one-fifth of society — have at least one persistent post-infection symptom that seriously interferes with their daily lives. It’s actually on the low side when compared to other estimates, like an April meta-analysis that puts the global long-Covid proportion closer to 50%, or a June CDC household survey that says 1 in 3.

Trusting him, Nathan Praschan, a psychiatric researcher at Massachusetts General Hospital, calls the more rigorous CDC study’s epidemiology one of the best he’s seen for using a control group for over a year to tease out the effects of Covid. Still, he thinks some people might have missed it by not showing up on medical records. Long Covid is defined by symptoms – psychiatric disorders and cognitive problems, to name just two – that could complicate seeking medical care, as well as the same social determinants of health that mean that Covid infection primarily affects some population groups is more likely. “So 1 out of 5 might be an underestimate.”

What about different definitions?

For example CDCs vs. WHOs. The CDC defines long-term covid, which it calls post-acute sequelae of SARS-CoV-2 infection (or PASC), as symptoms that last four weeks after initial infection. The World Health Organization lets the clock tick after three months. Praschan said it makes sense to be inclusive, as on the earlier page, while data is still being collected to avoid losing important information from these patients.

There may be discrepancies in the data.

While some UK studies have relied on records provided by a national health system, others have selected responses from a smartphone app asking people about their post-Covid symptoms. This limits respondents to people who have smartphones and are also motivated to share how they feel.

The large numbers in the CDC report give strength to the analysis, lead epidemiologist Lara Bull-Otterson told STAT. “Although all studies have limitations, we believe the strengths of the data and analysis are solid and also supported by previous research,” she said. “Future research is always needed to support and expand on the findings of this study.”

Bruce Levy, chief of pulmonary and critical care medicine at Brigham and Women’s Hospital, doesn’t think the 20 percent estimate is rock solid because studies in the US and other parts of the world have varied widely. “Even if it’s single digits at the end of the day, it’s still a lot of people once formal case definition and a real prevalence study can be done. But it’s very difficult to give a solid number.”

While the size of the CDC study is impressive, the source of the data has limitations, said epidemiologist Priya Duggal of the Johns Hopkins Bloomberg School of Public Health. Medical records reflect only those people who sought help and whose symptoms were coded in their medical records. Such data does not include people who did not have access to health care, did not seek it, or gave it up because they thought there was no help for their crazy symptoms.

“That doesn’t mean the data is wrong. That doesn’t mean what we see doesn’t matter,” she told STAT. “It just means you might be dealing with a different group of people.”

Even with caveats, she finds the data fairly consistent for a range of 20% to 30% of people with long-term Covid symptoms. “It’s still a significant number of people. For me, that’s the take-home point,” she said. “The second point is that it’s real.”

Long Covid is a constellation of diseases that manifest themselves in different ways.

Symptoms related to long Covid hit body from head to toe: brain fog, fatigue, shortness of breath, digestive problems, muscle weakness. Symptoms vary in severity and number depending on the study. But most patients don’t necessarily have all of them. Some patients do not have debilitating fatigue but may report persistent digestive issues that they did not have prior to contracting Covid.

Some long covid may be something else.

Because long covid is so diverse and common, it is possible for some doctors to misattribute symptoms to long covid and overlook a diagnosis of another disease. Or because life-saving measures in intensive care units can be like a train wreck for the body, it is difficult to tease treatment out of the disease.

Some long covid are hidden from bystanders.

“Some of that will be visible like, oh, they’re weak, they’re sickly, they can’t walk, they can’t go upstairs,” Duggal said. “Then there’s also long Covid where you have kidney damage now and the average person walking down the street doesn’t know that.”

She has heard people say they don’t know anyone who has had Covid for a long time. “I think you probably do.”

Long Covid is not all debilitating.

The CDC definitions capture thousands who fit the worst-case picture of the long Covid: formerly healthy people who are no longer able to function. But its prevalence estimate also includes anyone reporting at least one symptom, Bruce Walker, director of the Ragon Institute of Massachusetts General Hospital, MIT and Harvard, reminded reporters on a recent call. Estimates can also capture a worsening pre-Covid condition such as asthma, an important consideration for the many people with underlying conditions before they contracted Covid.

What’s next?

The CDC’s Bull-Otterson called for routine screening for long Covid and better definition so risk factors can be identified and treatments developed. The implications of vaccination and the wild card of variants also need to be understood.

Long Covid has the potential to widen existing health gaps, Boston University School of Social Work’s Linda Sprague Martinez said in a video call with reporters, pointing to a map of counties with high case numbers but few long Covid clinics. “We don’t want to wait,” she said. “It will be very important for us to move forward,” she said.

OK, what can we say now?

Long Covid estimates will certainly evolve and perhaps be refined into the systems they affect: cardiopulmonary, digestive, musculoskeletal, or neurological, including autonomic forces that control breathing, heart rate, and other unconscious functions. If, as experts say, catching Covid now or again is inevitable, Covid will likely long follow in a fraction of the cases, disabling another fraction of those people. Recent studies suggest that Covid infections precede the risk of certain other chronic diseases, such as type 2 diabetes, but the mechanism is not clear. Even if the world wasn’t ready for a pandemic, it somehow has to deal with its aftermath.

“We see that people are still having long-term symptoms two years later. So if that’s true and people can continue to get infected, that’s going to be with us for quite a while,” Duggal said.

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