Although not everyone recovers, a recent study analysing nearly 2m patient records in Israel concludes that for most people, the troubling symptoms that persist after a mild Covid infection fade away after about a year.
Just as estimates of long Covid’s prevalence have varied widely, so have conclusions about a variety of symptoms, reports STAT.
Covid infections reach into multiple organ systems, as does long Covid. Scientists have reported on some neuropsychiatric conditions lingering for two years, for example, but the team from the KI Research Institute wanted to paint a broader picture of long Covid’s duration.
“When we started this study there was a lot of uncertainty regarding the long-term effects of the pandemic and there was a fear that a large proportion of infected individuals will have long-lasting symptoms and emergence of new morbidities,” the study’s senior author Maytal Bivas-Benita and lead author Barak Mizrahi said.
“As we analysed the data, we were surprised to find only a small number of symptoms that were related to Covid and remained for a year post-infection and the low number of people affected by them.”
For their paper that was published in The BMJ, the researchers analysed 1 913 234 patient records from Maccabi Healthcare Services, a large health maintenance organisation in Israel whose members were tested for Covid-19 from March 2020 to October 2021, when the original virus and the Alpha and Delta variants were circulating.
After compiling a list of 70 long Covid symptoms, they looked for them at different time points, comparing the nearly 300 000 patients who tested positive to comparable patients who tested negative for Covid-19, excluding anyone hospitalised for the illness.
Studying non-hospitalised patients better reflects the vast majority of people who contract Covid, they said, also making it easier to tease out effects caused by the virus and not by intensive care treatments like ventilators.
“We wanted to understand what the long-term effects of this infection are on the majority of the population and whether we should expect a significant burden on healthcare providers,” they added.
Throughout the year of follow-up, patients with mild Covid-19 had an increased risk of problems including loss of smell and taste, concentration and memory impairment, breathing difficulties, weakness, palpitations, strep throat and dizziness.
Later in the year, health records showed more hair loss (particularly among women), chest pain, cough, muscle aches and pains, and respiratory disorders among Covid patients. But for most people, these problems also cleared up by the end of one year.
Vaccinated people were at lower risk of developing breathing difficulties after breakthrough infections – the most common problem after mild infection, along with weakness – compared with unvaccinated people, but their risk was similar for other conditions. People from 41 to 60-years-old had more health problems than people in other age groups, and shortness of breath continued to be a problem for those over 60.
Children had fewer long Covid symptoms than adults, and most of those issues were gone after a year. “This is a reassuring large population medical record study,” said Michael Absoud, honorary reader in the Department of Women & Children’s Health at King’s College London who was not involved in the study. “It confirms that in children, of the small proportion who have prolonged persistent symptoms post SARS-CoV-2 infection, most show a very good recovery.”
There were minor differences between men’s and women’s risk of outcomes, and findings remained consistent across the SARS-CoV-2 variants that emerged before Omicron.
Ziyad Al-Aly, clinical epidemiologist at Washington University in St Louis, believes the study’s message may be too optimistic, owing to its design. Comparing people who test positive to people who test negative may not account for the reason people are taking Covid tests, he said. Someone with cancer might need to test before starting chemotherapy, or someone else might need surgery for another reason.
“Better designs would be needed to more confidently elevate our understanding, to actually deepen our understanding of the the toll and scale of the condition and the trajectory of the health performance of the individual affected with long Covid over the the ensuing year after that infection,” said Al-Aly, who is also chief of research and development at the VA St Louis Health Care System.
“It doesn’t mean that some people are not improving. We see a big improvement in some individuals … I wish this were normally the case, but it’s really too rosy to be true.”
In response, the study authors said it’s important to remember that PCR tests to detect Covid-19 were offered to all Israeli citizens free, without needing a referral, throughout the entire study period. That meant 76% of Maccabi Healthcare Services’ members took at least one PCR test during the study period.
And they say “chances are minimal” that those test-negative patients would be more likely to have symptoms like long Covid, because any chronic conditions they had at baseline were matched to test-positive patients who also had them. And, they pointed out, infectious diseases other than Covid were rare during social distancing and lockdown during the study period.
The researchers acknowledged that not everyone recovers. And their results come from one country.
“We are not claiming there are no patients who suffer from long Covid symptoms (like dyspnea, weakness, cognitive impairment etc.),” they said. “This does not contradict evidence that a small number of patients do suffer from long lasting symptoms, as seen in this analysis.”
Next on their research agenda: evaluating the effects of the Omicron strain and assessing the prevalence and severity of outcomes following reinfections.
Study details
Long Covid outcomes at one year after mild SARS-CoV-2 infection: nationwide cohort study
Barak Mizrahi, Tamar Sudry, Natalie Flaks-Manov, Yoav Yehezkelli, Nir Kalkstein, Pinchas Akiva, Anat Ekka-Zohar, Shirley Shapiro Ben David, Uri Lerner, Maytal Bivas-Benita, Shira Greenfeld.
Published in The BMJ on 11 January 2023
Abstract
Objectives
To determine the clinical sequelae of long Covid for a year after infection in patients with mild disease and to evaluate its association with age, sex, SARS-CoV-2 variants, and vaccination status.
Design
Retrospective nationwide cohort study.
Population
1 913 234 Maccabi Healthcare Services members of all ages who did a polymerase chain reaction test for SARS-CoV-2 between 1 March 2020 and 1 October 2021.
Main outcome measures
Risk of an evidence based list of 70 reported long Covid outcomes in unvaccinated patients infected with SARS-CoV-2 matched to uninfected people, adjusted for age and sex and stratified by SARS-CoV-2 variants, and risk in patients with a breakthrough SARS-CoV-2 infection compared with unvaccinated infected controls. Risks were compared using hazard ratios and risk differences per 10 000 patients measured during the early (30-180 days) and late (180-360 days) time periods after infection.
Results
Covid-19 infection was significantly associated with increased risks in early and late periods for anosmia and dysgeusia (hazard ratio 4.59 (95% confidence interval 3.63 to 5.80), risk difference 19.6 (95% confidence interval 16.9 to 22.4) in early period; 2.96 (2.29 to 3.82), 11.0 (8.5 to 13.6) in late period), cognitive impairment (1.85 (1.58 to 2.17), 12.8, (9.6 to 16.1); 1.69 (1.45 to 1.96), 13.3 (9.4 to 17.3)), dyspnoea (1.79 (1.68 to 1.90), 85.7 (76.9 to 94.5); 1.30 (1.22 to 1.38), 35.4 (26.3 to 44.6)), weakness (1.78 (1.69 to 1.88), 108.5, 98.4 to 118.6; 1.30 (1.22 to 1.37), 50.2 (39.4 to 61.1)), and palpitations (1.49 (1.35 to 1.64), 22.1 (16.8 to 27.4); 1.16 (1.05 to 1.27), 8.3 (2.4 to 14.1)) and with significant but lower excess risk for streptococcal tonsillitis and dizziness. Hair loss, chest pain, cough, myalgia, and respiratory disorders were significantly increased only during the early phase. Male and female patients showed minor differences, and children had fewer outcomes than adults during the early phase of Covid-19, which mostly resolved in the late period. Findings remained consistent across SARS-CoV-2 variants. Vaccinated patients with a breakthrough SARS-CoV-2 infection had a lower risk for dyspnoea and similar risk for other outcomes compared with unvaccinated infected patients.
Conclusions
This nationwide study suggests that patients with mild Covid-19 are at risk for a small number of health outcomes, most of which are resolved within a year from diagnosis.
See more from MedicalBrief archives:
More than half of patients suffer long Covid symptoms – SA study
WHO estimates 17m long COVID cases in Europe and urges action
One in every eight adults likely infected with long COVID, large study finds
Long COVID impacts heart, lung and kidney – Scottish study