Which coronavirus patients are most at risk for developing long Covid?
A new analysis of research conducted during the first two years of the pandemic helps crystallize some answers that have been emerging.
It found that patients over 40, those with previous health issues and those who had a severe coronavirus infection had greater risk of developing long Covid. And it affirmed a growing consensus that vaccination lowers that risk.
The analysis, conducted by a team of researchers in Britain and published in the journal JAMA Internal Medicine, looked at 41 studies published between the beginning of the pandemic and Dec. 5, 2022. The studies, which had all been peer-reviewed, involved a total of 860,783 patients.
The report evaluated the patients’ risk of post-Covid symptoms — including shortness of breath, fatigue, brain fog, headache, and loss of taste and smell — more than three months after their infection.
People who received two doses of a Covid vaccine before becoming infected were 43 percent less likely to develop long Covid. The analysis did not look at the role of boosters.
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The authors wrote that the emerging evidence suggested that vaccination reduced the risk of long-term symptoms “even in individuals with other risk factors, such as older age or high B.M.I.”
Other studies that were not included in the analysis have also suggested that vaccines can reduce, though not eliminate, the risk of long Covid.
Risk factors analyzed in the paper included:
Women were one and a half times as likely as men to develop long Covid. The authors and other researchers have suggested several possible reasons for this, including that hormone levels or disruption in hormone production may perpetuate inflammation caused by the initial infection and that higher levels of some antibodies in women might contribute to lingering symptoms.
Being over 40
The long Covid patients in the analysis were about 20 percent more likely to be older than 40. The analysis found that people 70 and older had the same risk as those who were 40 to 69, but the researchers suggested that might be because people over 70 were more likely to die from their initial infection.
People were at increased risk for long Covid if they were obese, the analysis found. Obesity, they wrote, often involves a metabolic inflammatory process that could prolong post-Covid health issues.
Being a smoker
Smoking was also a risk factor, the researchers found, although they said it was unclear if that was because of the smoking itself or illnesses associated with smoking.
Having previous medical conditions
Of the medical issues analyzed in the study, immunosuppressive conditions appeared to lead to the greatest increased risk of long Covid. People with chronic obstructive pulmonary disease, ischemic heart disease or asthma faced the next highest levels of increased risk. There was also elevated risk of long Covid for people with anxiety, depression, chronic kidney disease or diabetes.
The sicker people were during their initial infection, the more likely they were to experience lingering health problems. Patients who were hospitalized, whether in intensive care or not, were nearly two and a half times as likely to develop long Covid than patients who were not hospitalized, the analysis found.
“Patients with previous critical illness represent a high-risk population, and their follow-up should reflect intensive plans for prevention, rehabilitation and treatment of the ongoing debilitating symptoms,” the authors wrote.
However, since a majority of people infected with the coronavirus have not needed to be hospitalized, there are greater numbers of long Covid patients whose initial infection was relatively mild.
Other research, not included in the analysis, has focused on more detailed biological characteristics. One study published in 2022 found that people were more likely to develop long Covid if, at the time of their infection, they had factors including certain autoantibodies — antibodies that mistakenly attack tissues in the body as they do in conditions like lupus and rheumatoid arthritis — or reactivated Epstein-Barr virus, a virus that infects most people and then usually becomes dormant.
The new analysis involved patients infected during waves of various coronavirus variants, but the authors did not analyze the variants separately.
“It is unlikely that the risk factors” associated with long Covid would change with new variants, they wrote.