Age does not increase susceptibility to COVID-19, but likely to effect severity of infection, study suggests
A group of scientists claim that age may not be linked to COVID-19 susceptibility after all. However, the claim that older people may be at risk of developing severe disease and dying of COVID-19 if they get it still holds true.
Old age is considered to be a risk factor for severe COVID-19. Epidemiological studies from Wuhan and Iceland had also shown that the susceptibility to COVID-19 varies with age.
Now, a group of scientists at the Hokkaido University claim that age may not be linked to COVID-19 susceptibility after all. However, the claim that older people may be at risk of developing severe disease and dying of COVID-19 if they get it still holds true.
The new study is published in the peer-reviewed journal Scientific Reports.
To conduct the study, the researchers modelled COVID-19 data from Japan, Italy and Spain. The countries were chosen because their data was easily available.
They then studied the data to find the link between age, susceptibility (risk of getting the disease) or severity (risk of dying of the disease).
As per a news release by the Hokkaido University, the COVID-19 mortality rates (deaths per 1,00,000 infected people) in Japan, Italy and Spain, as of May 2020, were 13.2, 382.3 and 507.2 respectively. However, despite the huge variation in the mortality rate, all three countries had similar age distribution of mortality (percentage of deaths in each age group).
To better understand the susceptibility to COVID-19, the researchers included factors such as interaction with other people and restrictions in the three countries.
The data showed that the robust age distribution in mortality in the three countries is not determined by susceptibility to infection but it does suggest a link between age, number of symptomatic infections and mortality rate. In other words, age may not decide if a person is more at risk of catching COVID-19, but it may have some effect on which patient may develop severe disease (if they get it) and die of it.
Lack of data
The authors suggested that the age-dependent mortality which is apparent in the three countries may just be because of the higher number of symptomatic infections that occurred in older people. However, since we don't have data on the rate of diagnosis of COVID-19 or the age-dependent symptomatic cases, nothing could be said for sure.
Additionally, to understand the mechanism behind the age-dependent mortality rate of COVID-19, accurate data for the age-dependent mortality rate is needed. The data used in the study might not cover all mortalities due to COVID-19.
The authors of the study also indicated a lack of case fatality rate in their data. This is because the total number of cases, which is needed to estimate the case fatality rate, is not yet clear when it comes to COVID-19. Changes in testing rate, case definition and selection bias make it difficult to even estimate the exact number of total COVID-19 cases.
The authors suggested that large scale epidemiological studies and identification of the infection are needed to remedy this problem and find out exactly how many people got infected by the disease in the first place.
For more information, read our article on COVID-19.
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