Finding should not be confused with long covid-related mortality as researchers did not analyse that, experts tell DTE
The findings of a new Covid-related study by researchers from the Indian Council of Medical research (ICMR) must be treated with caution, experts have told Down to Earth (DTE).
The mortality rate among 14,419 former COVID-19 patients across 31 Indian medical centres was 6.5 per cent a year after being discharged from hospital, according to the study.
Experts DTE spoke to, however clarified that this study focused on all-cause mortality and the deaths cannot be attributed to just COVID-19 alone. This is primarily because the ICMR researchers did not test control groups due to the inability to identify people without being infected with COVID-19 at least once.
In scientific research, a control group is meant to establish the influence of an independent factor with comparisons to people with similar baselines.
Therefore, according to the ICMR study, the data only established an all-cause mortality rate of 6.5 per cent, which may or may not be attributable to COVID-19 due to the patient’s prior comorbidities. An all-cause mortality means death can occur due to any cause.
Instead, the researchers looked at a small subset of people with comorbidities post-hospital charge who had certain persistent symptoms at four weeks after the initial COVID-19 diagnosis.
“Hence, we did not establish whether the deaths were directly related to COVID-19 recovery after hospitalisation per se, and hence to say that would be misleading. It is a well-known fact that anyone who is hospitalised with a serious condition has a higher chance of mortality later on, for any reason,” an ICMR researcher closely involved with the study conducted between September 2020 and February 2023, informed DTE.
Rajeev Jayadevan, co-chairman of the National Indian Medical Association COVID Task Force said the mortality rate of 6.5 per cent translates to one out of 15 people, which is a significant number.
However, this cannot be generalised to all patients and must be viewed with caution, he said.
“The level of sickness depends on the type of hospital, and the population it is serving, and cannot be generalised to all hospitals. For instance, in a wealthy suburb, relatively healthy people with COVID-19 might be admitted to a private hospital simply for observation, or at their own request. The case might be different in a crowded government-run referral hospital that receives only the sickest patients from the whole region,” he said.
So what exactly does a one-year post-discharge mortality rate of 6.5 per cent signify among patients with commorbities?
On the key takeaway of the ICMR study, the researcher elaborated, “Of the patients who died, about 50 per cent died within 28 days of discharge and the chances decrease as time goes on. The most susceptible age group is those who are 60+ with comorbidities. An easily modifiable factor would be vaccination. Vaccine protection helps reduce disease severity during hospitalisation stay as well and our study ventured into what happens beyond discharge.”
For most people, 60 per cent protection was conferred by vaccination before the COVID-19 infection, the paper said.
Furthermore, the paper mirrors data generated from other studies. A 2022 systematic review of 48 studies examining hospital readmissions, nine studies assessing post-discharge all-cause mortality, and 34 studies examining both outcomes found that the one-year post-discharge all-cause mortality rate of COVID-19 patients was 7.87 per cent. The mortality happened within the first 30 days post-discharge.
There are other caveats to consider too.
Experts said this statistic was not meant to alarm people with long covid as some media reports had. They also said it was not intended to contradict previous excess death rate studies and present alarming figures.
For instance, the paper reported that the odds of dying after the first follow-up at four to eight weeks were higher among those with comorbidity and those who reported Post Covid Condition as defined by the researchers.
However, to arrive at this conclusion of a one-year post-discharge mortality of 6.5 per cent, “neither did we consider Post Covid Condition(PCC) nor did we check symptoms of long-term COVID,” the ICMR researcher part of ICMR’s clinical studies and trials unit said.
The operational definition of PCC used in this study is not an exact match to either the WHO or CDC definitions. “While the WHO definition for PCC says that we have to wait for three months and then check if the symptoms persist for two months, it says long covid symptoms persist post-three months after initial infection. However, our study only did a symptomatic assessment at four weeks’ time, not after that,” the ICMR researcher said, highlighting the limitation.
“We did not examine long covid symptoms and we did not check whether their symptoms persisted beyond three months. Some of them may have recovered as well,” the ICMR researcher explained and refuted claims in the media of the study indicating a long covid mortality rate.
The comorbidities were considered an underlying factor influencing the mortality rate. The study’s participants had hypertension, diabetes, chronic cardiac disease, chronic kidney disease, asthma, malignancy, chronic pulmonary disease, chronic liver disease, stroke, tuberculosis, chronic neurological disease, rheumatological disease, autoimmune disease, hematological disorders, HIV, hepatitis B or C infection.
“This should not be confused with long covid-related mortality because their comorbid prior illness was perhaps severe to begin with. In other words, these symptoms could have also been the result of their underlying illness rather than those induced by COVID-19. Therefore, people with long covid need not worry when they see the relatively high death rates in that subgroup,” Jayadevan told DTE, reiterating the ICMR study’s stance.
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