Several studies suggest that some people are at a higher risk for developing long COVID-19 than others. The factors that make them more likely to experience persistent symptoms vary from sex and age to the levels of a particular antibody.
Long COVID-19 is a condition that can last weeks or months after infection. The symptoms can include tiredness or fatigue, "brain fog" or difficulty thinking or concentrating, headache, sleep problems, change in smell or taste, and others. One in eight (12.7%) COVID-19 patients are likely to experience long-term symptoms, a study from the Netherlands has reported.
An analysis published in the British Medical Journal last month revealed that about 5% of patients, or 27 million people worldwide, still report smell or taste dysfunction six months after getting COVID-19.
There are several hypotheses on why symptoms do not go away weeks or months after catching COVID-19. As Nature reports, the research suggests that the virus causes trouble by stimulating the immune system, or infection generates antibodies that mistakenly attack the body's own proteins.
While there is no clear answer to why we have long COVID, studies suggest why some people are more likely to suffer from persistent symptoms.
Levels of nucleocapsid
A study on long COVID-19 from Stanford School of Medicine found that symptoms of COVID-19 lasted longer in people who had lower levels of a specific antibody nucleocapsid in the first week of diagnosis. Nucleocapsid, or N protein, surrounds the virus's genetic material.
Researchers also found that people with a history of lung disease, including asthma or chronic obstructive pulmonary disorder, took longer to see their symptoms resolve completely.
The study followed 617 people diagnosed with COVID-19 at Stanford Health Care between March 2020 and February 2021. Due to the time frame, most of them were not vaccinated.
The most common lasting symptoms reported by the participants of the study one month after diagnosis included a loss of taste or smell, fatigue, headache, and body aches. By six months, it was fatigue, headache, and body aches.
The study's authors concluded that the severity of the initial disease did not affect the likelihood of developing long COVID. The patient's ethnicity, age, or sex also did not put them at a higher risk of having persistent symptoms.
Females might be more at risk
University College London's (UCL) researchers identified predisposing risk factors for long COVID after examining anonymized data from 1.2 million primary health records across the UK and ten long-term population-based studies involving 45,096 participants.
The researchers found that females were 50% more likely to report persistent symptoms than males. Among other risk factors were middle age, poor pre-pandemic mental or physical health, asthma, and obesity.
Another research from the University of Parma demonstrates that females were more symptomatic than males in the acute phase of COVID-19 and at follow-up after five months. The most common persistent symptoms in women were difficulty breathing, fatigue, chest pain, and palpitations.
Long COVID in hospitalized children
More than 1 in 4 children hospitalized with acute COVID-19 or MIS-C, a severe COVID-related condition, experienced persistent symptoms or activity impairment for at least two months, a study published in the journal Pediatrics revealed. In addition, those with MIS-C and respiratory conditions or obesity were at higher risk of a prolonged recovery.
MIS-C, or multisystem inflammatory syndrome in children, is a condition where different body parts, including the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs, can be inflamed.
According to the Centers for Disease Control and Prevention (CDC), it is not known what causes MIS-C, but it is known that many children with MIS-C had the virus that causes COVID-19 or had been around someone with COVID-19.
The study shows that the most common symptoms for children hospitalized with COVID-19 were fatigue, shortness of breath, cough, headache, muscle and body aches, and fever.