Long Covid hampers millions worldwide, study shows

Long Covid eases with time, according to a study that found about 1% of coronavirus patients had persistent symptoms for a year or more.

In the first rigorous assessment of the magnitude of long Covid on a global scale, researchers found 6.2% of people who had Covid-19 in the pandemic’s first two years experienced at least one of three main groups of symptoms three months later. Of those patients, 15% were still afflicted after a year.

Though the probability of having chronic health problems from Covid is relatively low, the vast number of cases — at least 670-million worldwide — leaves a substantial burden of disability, said Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, where the study was conducted. 

Long Covid’s effects are, on average, similar to what occurs after a moderate-to-severe traumatic brain injury or complete deafness, said Theo Vos, a professor of health metrics sciences at the university, who led the study. 

The study, published Monday in the journal JAMA,

is based on data from 1.2-million Covid patients in 22 countries gathered from 54 studies and two medical record databases, including from the US Veterans Affairs health system. More than 200 ailments have been linked to long Covid, but the study in JAMA collated information on three common clusters of symptoms.

It found that three months after a coronavirus infection, 3.7% of patients had ongoing respiratory problems, 3.2% had persistent fatigue with bodily pain or mood swings and 2.2% had cognitive problems, after adjusting for their health status before Covid.

‘Small Minority’

It’s not uncommon for Covid patients to experience persistent symptoms for a month, but most have fully resolved or diminished significantly after three months, said Sarah Ryan, a doctor at Columbia Primary Care in New York. 

Ryan, who has been caring for long Covid patients for more than two years, says that in her experience “a handful” have severe problems a year after their infection. “But the good news for the public is that they’re a small minority,” she said.

The risk of getting durable long Covid symptoms increases with the severity of the acute infection, the study in JAMA found. The average duration of long Covid was nine months for people who were hospitalised for the coronavirus, compared with four months for people who fought off the virus at home. 

Among patients older than 20 who caught Covid three months earlier, persistent symptoms occurred in 10.6% of women and 5.4% of men. 

Risk Factors

It’s not known yet what causes long Covid, though several risk factors are associated with the condition, said Michael Peluso, an infectious diseases physician-scientist at the University of California, San Francisco, who’s been studying Covid’s lingering effects in patients since March 2020.

“Women tend to be more affected than men,” Peluso told a university forum on Thursday. The probability of developing long Covid is higher among people who are “middle age, rather the extremes of age,” those with pre-existing medical conditions and obesity, and in individuals with lower socioeconomic status and poorer access to healthcare, he said. 

The latest analysis accounts for Covid cases through the end of 2021, before Omicron variants fuelled an unprecedented surge in infections. UK data suggest the hyper-infectious Omicron clan of strains is much less likely to cause long Covid than the delta variant that preceded it. 

Long haul symptoms aren’t the only health threat to Covid survivors. Diabetes and life-threatening conditions including heart attacks, stroke and kidney damage are more common in Covid patients than those who avoided the pandemic disease. 

“The pandemic will raise the baseline risk of disease and disability to a new level,” said co-author Ziyad Al-Aly, chief of research & development at the Veterans Affairs St. Louis Healthcare System, whose own studies have led to important early findings about long Covid. 

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