About four crore Indians suffered long COVID symptoms during the last two years of the pandemic, according to a study, not peer-reviewed yet.

Long COVID is defined as having new or ongoing symptoms four weeks or more after the start of the disease. Symptoms include fatigue, shortness of breath, loss of concentration and joint pain. The symptoms can adversely affect day-to-day activities, and in some cases can be severely limiting.

In the study, a team of international researchers jointly analysed countries for the occurrence of three major symptom clusters of long COVID-- fatigue, cognitive problems, and shortness of breath. They pooled data from more than 44 global studies and medical record databases and also from the Global Burden of Diseases (GBD) study, from 204 countries.

The findings, posted on a preprint site, showed that globally, in 2020 and 2021, 144.7 million people suffered from at least one of the three symptoms. Respiratory symptoms like cough, wheezing and shortness of breath was the highest and experienced by 60.4 per cent of people.

More than 50 per cent suffered from fatigue -- having body pain, being tired always and getting easily upset. Cognitive problems like loss of memory, confusion, and feeling disoriented were experienced by 35.4 per cent of people.

Those with milder acute COVID-19 cases had a quicker estimated recovery of 3.99 months than those admitted for the acute infection at 8.84 months. At 12 months, 15.1 per cent continued to experience long COVID symptoms.

The risk of long COVID was found to be greater among females between 20 and 29 years and in those with more severe initial infections. "This pattern by age and sex is distinct from that of severe acute infection, which affected more males and increased with age," the researchers said.

Further, the researchers also found that long COVID also affected "a lower but substantial number of children", while severe acute infection has been very uncommon at younger ages. These differences suggest that the underlying mechanism of long COVID may be different from that of the severity of acute infection, the researchers said.

"The occurrence of debilitating ongoing symptoms of COVID-19 is common. Knowing how many people are affected, and for how long, is important to plan for rehabilitative services and support to return to social activities, places of learning, and the workplace when symptoms start to wane," they added.