(CNN) — The majority of long Covid symptoms resolve within the first year after infection for people with mild cases of Covid-19, according to a large study conducted in Israel.
“Mild disease does not lead to serious or chronic long term morbidity in the vast majority of patients,” said study coauthor Barak Mizrahi, a senior researcher at KI Research Institute in Kfar Malal, via email.
The study, published Wednesday in the journal The BMJ, compared thousands of vaccinated and unvaccinated people with mild Covid symptoms who were not hospitalized with people who tested negative for the virus. Long Covid was defined as symptoms that continue or appear more than four weeks after an initial Covid-19 infection.
“I think this study is reassuring in that most ongoing symptoms following COVID do improve over the first several months following the acute infection,” said Dr. Benjamin Abramoff, director of the Penn Medicine Post-COVID Assessment and Recovery Clinic, via email. He was not involved in the study.
But not for everyone. Abramoff said his clinic continues to see many patients with severe long Covid symptoms lasting longer than one year following their infection.
“This is particularly true in those individuals who had severe persistent symptoms early after their acute infection,” said Abramoff, who leads the American Academy of Physical Medicine and Rehabilitation’s long Covid collaborative.
Dr. Jonathan Whiteson, an associate professor of rehabilitation medicine at the NYU Grossman School of Medicine, sees the same in his clinic.
“I continue to see many patients from the ‘first wave’ of COVID who had mild to moderate acute COVID (and were) never hospitalized who have significant persistent and functionally limiting symptoms nearly 3 years later,” said Whiteson via email. He was not involved with the study.
A large data set
Israeli researchers analyzed the medical records of nearly 300,000 people diagnosed with mild cases of Covid-19 and compared their health over the next year with approximately 300,000 people who didn’t have Covid. The average age of those who tested positive for Covid was 25 years, and 51% were female.
Researchers looked for 65 conditions that have been associated with long Covid and divided those into two time frames: early, or the first 30 to 180 days after catching Covid; and late, or 180 to 360 days post infection.
After controlling for age, sex, alcohol and tobacco use, preexisting conditions, and the different variants of Covid-19, researchers found a significant risk of brain fog, loss of smell and taste, breathing problems, dizziness and weakness, heart palpitations, and strep throat in both the early and late time periods.
Chest pain, cough, hair loss, muscle and joint pain, and respiratory disorders were significantly increased only during the early phase, according to the researchers.
Difficulty with breathing was the most common complaint, the study found. Being vaccinated reduced the risk of respiratory issues, but researchers found vaccinated individuals had a “similar risk for other outcomes compared with unvaccinated infected patients,” according to the study.
“Because of the study’s size, it was possible to look at the change in symptom prevalence over time and the effects of other factors on persistent symptoms,” said Dr. Peter Openshaw, a professor of experimental medicine at Imperial College London, in a statement.
“Smell disorder typically resolved at about 9 months, but when they were present concentration and memory changes tended to be more persistent,” said Openshaw, who was not involved in the study.
Only slight differences appeared between men and women in the study, but children had fewer early symptoms than adults, which were mostly gone by year’s end. No real differences were found between the original wild-type of SARS-CoV-2 (March 2020 to November 2020), the Alpha variant (January 2021 to April 2021) and the Delta variant (July 2021 to October 2021).
“Patients with mild Covid-19 had an increased risk for a small number of health outcomes, with only a few symptoms persisting a year from SARS-CoV-2 infection and their risk decreased with time from infection,” Mizrahi said via email.
However, “we are not claiming there are no patients who suffer from long COVID symptoms like dyspnea (difficulty breathing), weakness, cognitive impairment etc.,” he added. “(Our study) does not contradict evidence that a small number of patients do suffer from long lasting symptoms as seen in this analysis.”
Limitations of the study
Researchers pointed to certain limitations in the study, such as the possibility of diagnostic errors or failure to record some milder symptoms over time. Abramoff agreed.
“This design of this study is not able to detect the severity of these symptoms, and there are potentially other missed patients due to using medical coding to detect persistent Long COVID symptoms,” Abramoff said.
It could also be difficult to apply the findings of the study to other countries, such as the United States, due to differences in how doctors code symptoms. For example, the study did not identify several conditions frequently found in long Covid clinics in the US, said Dr. Monica Verduzco-Gutierrez, professor and chair of the department of rehabilitation medicine at the Long School of Medicine at UT Health, San Antonio.
“The most common symptom of Long COVID is fatigue, and that was not on this list. Also missing was post-exertional malaise, dysautonomia/POTS, or ME/CFS. These are some of the major presentations I am seeing in my clinic population, so it is a major limitation of this study to not have those outcomes,” said Verduzco-Gutierrez, who was not involved in the new study.
Post-exertional malaise is an overwhelming exhaustion after even a minimal amount of effort. Unlike regular exhaustion, it can take days to weeks for a person to recover, and the malaise can be reactivated if activity is resumed too quickly.
Postural orthostatic tachycardia syndrome, or POTS, is a bump in heart rate after sitting up or standing that can lead to dizziness or fainting. It’s a form of dysautonomia, a disorder of the autonomic nervous system. “There is usually no cure for dysautonomia,” according to the National Institute of Neurological Disorders and Stroke.
Myalgic encephalomyelitis/chronic fatigue syndrome, or ME/CFS, is a serious long-term illness, in which people have overwhelming fatigue that is not improved by rest. The condition can impact sleep and thinking processes, cause pain in many parts of the body, and keep people from doing most daily activities.
Responding to this concern, Mizrahi told CNN that “post exertional malaise was not included in this study as it is not a diagnosis that commonly prescribed in Israel.” In addition, he said, dysautonomia/POTS was only assigned an International Classification of Diseases, or ICD medical code, as of October 2022, so it too was not included in the study.
However, symptoms of POTS and other conditions may have been included under more general categories such as cardiac arrhythmias or palpitations, he said.
In addition, Mizrahi said fatigue was coded under “weakness” in the study. In fact, researchers found weakness to be the second most common symptom reported in the study, and it continued to plague people ages 19 to 60, for months.