For some, a coronavirus infection means a pesky cough, low fever and fatigue for a week, but for others, the virus sets up camp and drowns them with symptoms that can last months.
Scientists call these individuals long-haulers, and now research suggests that the number of symptoms a person has might be able to predict how long the course of someone’s disease could last.
In a study of more 4,000 people from the U.S., U.K. and Sweden, researchers found that having more than five symptoms during the first week of coronavirus illness was associated with what they call “Long-COVID.”
And of the thousands of participants, those who experienced symptoms for more than 28 days — what the researchers deemed a long infection — were “consistently older, more female and were more likely to require hospital assessment” than those who reported symptoms for less than 10 days.
The study has yet to be peer reviewed. It was published Oct. 21 in the pre-print medRxiv.
“At the population level, it is critical to quantify the burden of Long-COVID to better assess its impact on the healthcare system and appropriately distribute resources,” the researchers from the University College London said in their paper.
“In our study, prospective logging of a wide range of symptoms allowed us to conclude that the proportion of people with symptomatic COVID-19 who experience prolonged symptoms is considerable, and relatively stable across three countries with different cultures,” they continued.
The researchers asked 4,182 people with COVID-19 between March 25 and June 30 to log their symptoms in a “COVID Symptom Study app” on their mobile devices.
In total, 558 people had symptoms that lasted more than 28 days, 189 people’s symptoms lasted more than 8 weeks and 95 individuals experienced symptoms for more than 12 weeks.
Meanwhile, 1,591 people had a short disease duration.
The five symptoms experienced during the first week of sickness that were most predictive of prolonged disease in both men and women were fatigue, headache, difficulty breathing, hoarse voice and muscle pains.
Asthma was the only “unique” pre-existing medical condition that provided “significant association with long-COVID,” the researchers said.
Other symptoms and conditions associated with “Long-COVID” were loss of smell, which was the most predictive symptom of prolonged disease in adults over 70, and increased body mass index, according to the study.
The researchers also analyzed “free text responses” from participants who sent them and learned that cardiac symptoms such as heart palpitations and rapid heartbeat were more common in long-haulers (6%) than people with short symptom experiences (0.5%).
Memory and concentration issues, as well as earaches and ear ringing were also more common among long-haulers — 4% versus 0.2% and 3.6% versus 0.2%, respectively.
Other significant findings in the study involve age and sex.
Risks of “Long-COVID” increased from 10% in 18-49 year olds to 22% in those older than 70. Prolonged disease duration also affected women (15%) more than men (10%), but women between 50 and 60 years of age had the highest chances of experiencing it.
However, the researchers note the gender disparities could be explained by more women using the app to report symptoms than men. People older than 70 were also under-represented in the study, “which could increase or decrease our estimate of the extent of Long-COVID.”
The study was incapable of exploring risk factors for COVID-19 beyond two months and the team was unable to analyze how different ethnicities played a role in disease duration.