NEW DELHI: Some of the country's top cancer doctors seem to have found a biological explanation for India's strikingly low COVID-19 mortality, a mystery that has puzzled scientists, researchers and policymakers the world over.
The answer, the doctors have analysed, could be the lesser propensity for deep vein clots among the Indian population.
The study by doctors at the Tata Memorial Centre, Mumbai has been published in the ICMR's Indian Journal for Medical Research and points out that deaths per million in India is considerably lower than in most other countries.
The COVID-19 deaths per million in India is 25, as of now, and the country has recorded 34,968 deaths so far with a total of 15,83,792 confirmed cases of infection. India’s case fatality rate -- at 2.2 % -- is among the lowest in the world when compared to other badly-hit countries in the pandemic.
Multiple studies from China, Europe and the US have shown that blood clots in deep veins are associated with COVID-19 deaths and the doctors from the Tata Memorial Centre have proposed that the lower incidence of such blood clots in warmer climates and latitudes closer to the equator might help account for the relatively low mortality in India.
These doctors have also stressed the need to reduce widespread anxiety related to the disease and suggested that strict lockdowns are not necessary.
"The lower population-level mortality from COVID-19 in India could form the basis of reducing the widespread anxiety related to this disease and for undertaking nuanced social-distancing measures and personal protective measures without enforcing strict lockdowns," the paper says.
Researches from various other countries have identified venous thromboembolism -- a condition in which a blood clot forms most often in the deep veins -- as an important cause of poor gaseous exchange and death in COVID-19 patients.
Studies have also found D-dimer -- a small protein fragment present in the blood after a blood clot is degraded -- to be an important predictor of mortality.
The Tata Memorial Centre doctors have shown indirect evidence for lower incidence of venous thromboembolism from India. Less than five in more than 20,000 women who receive tamoxifen, an anti-breast cancer drug, at the Tata Memorial Centre annually, develop clots - a known complication of this drug.
The analysis has also highlighted that in a randomized study from India evaluating venous thromboembolism prophylaxis during surgeries showed that the incidence of venous thromboembolism in the control arm -- the group of patients who did not receive drugs to prevent clotting -- was also low.
Speaking to The New Indian Express, Dr Rajendra A Badwe, Director, Tata Memorial Centre, who is also the lead author of the analysis, pointed out that the US with one-fourth of India’s population has recorded five times more deaths than us.
"There has to be an explanation for this vast difference since it's the same virus and it could be because of environmental reasons affecting a biological phenomenon as our analysis shows," he said.
Dr Badwe underlined that the infection-related mortality was higher in Indians in the UK -- for instance -- which further suggested that it may not be genetic pre-disposition but environmental reasons, which triggers blood clotting in colder countries, leading to higher COVID-19 deaths.
"So, in our understanding while taking precaution to prevent contracting the infection should be the norm -- there is no need to panic and extend restrictive measures like lockdowns,” he said.