The coronavirus is the most deadly if you are older and male – new data indicates the risks

For every 1,000 people infected with the coronavirus who are under the age of 50, almost no one will die. For people in their fifties and early sixties, about five will die – more men than women. The risk then climbs steeply as the years build up. For every 1,000 people in their mid-seventies or older who become infected, around 116 will die. These are the sharp statistics obtained from some of the first detailed studies on the mortality risk for COVID-19.

Trends in coronavirus death by age have been evident since the beginning of the pandemic. Research teams looking at the presence of antibodies to SARS-CoV-2 in people in the general population – in Spain, England, Italy and Geneva in Switzerland – have now quantified that risk, says Marm Kilpatrick, an infectious disease researcher. the University of California, Santa Cruz.

“It gives us a much sharper tool when we ask what the impact might be on a particular population that has a particular demographic,” Kilpatrick says.

The studies show that age is by far the strongest predictor of the risk of an infected person dying – a metric known as the infection-lethal ratio (IFR), which is the proportion of people infected with the virus, including those who were not tested or showed symptoms, who will die as a result ..

“COVID-19 is not only dangerous for older people, it is very dangerous for people in their mid-fifties, sixties and seventies,” says Andrew Levin, an economist at Dartmouth College in Hanover, New Hampshire, who t has estimated that getting COVID -19 is more than 50 times more fatal to a 60-year-old than driving a car.

But “age can not explain everything”, says Henrik Salje, an epidemiologist of infectious disease at the University of Cambridge, UK. Gender is also a strong risk factor, with men dying from the coronavirus almost twice as often as women. And differences between countries in the lethal estimates for older age groups suggest that the risk of coronavirus death is also linked to underlying health conditions, the capacity of health care systems, and whether the virus is spread among people living in elderly care facilities,

Older men more at risk

To estimate the risk of mortality by age, researchers used data from anti-body performance studies.

In June and July, thousands of people across the UK received a pinprick antibody test in the mail. Of the 109,000 randomly selected adolescents and adults who took the test, some 6% had antibodies to SARS-CoV-2. This result was used to calculate a total IFR for England of 0.9% – if 9 deaths in every 1,000 cases. The IFR was close to zero for people between the ages of 15 and 44, increasing to 3.1% for those aged 65-74 and to 11.6% for everyone older. The results of the study were posted to the medRxiv preprint server¹.

Another study from Spain, which began in April, and tested for antibodies in more than 61,000 residents in randomly selected households, observed a similar trend. The total IFR for the population was about 0.8%, but it remained close to zero for men under 50, before rising rapidly to 11.6% for men aged 80 and older; it was 4.6% for women in that age group. The results also showed that men die more often from infection than women – the gap increases with age.

“Men are twice as likely as women,” said Beatriz Pérez-Gómez, an epidemiologist at the Carlos III Institute of Health in Madrid, who was involved in the Spanish study. The results are also posted to the medRxiv server².

Differences in the male and female responses of the immune system may explain the divergent risks, says Jessica Metcalf, a demographer at Princeton University, New Jersey. “The female immune system may have an edge by detecting pathogens just a little earlier,” she says.

The immune system can also cause the much higher risk of older people dying from the virus. As the body ages, it develops low levels of inflammation, and COVID-19 can push the already overworked immune system over the edge, Metcalf says. Less outcomes for people with COVID-19 are often associated with an increased immune response, she says.

The study in England also compared results from different ethnic groups. Statistics on mortality and morbidity suggest that Black and South Asian people in England die more often than in hospital. But the analysis, led by Helen Ward, an epidemiologist at Imperial College London, found that although Black and South Asian people were infected much more often than white people, they were less likely to die from COVID-19.

Land differences

Researchers note that there is a clear difference in IFR estimates between some countries, especially for people aged 65 and over³. For example, an anti-prevalence survey in Geneva estimates an IFR of 5.6% for people aged 65 and over⁴. This figure was lower than estimated in Spain, which comes to about 7.2% for men and women aged 80 or over, and in England, which found an IFR of 11.6% for people aged 75 or older.

There can be many explanations for the differences, says Andrew Azman, an epidemiologist of infectious disease at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, who was part of the Geneva study.

Countries with higher rates of co-morbidities, such as diabetes, obesity and heart disease, will have a higher IFR. People with health care systems that can better deal with people who are seriously ill with COVID-19, or where hospitals were not overwhelmed at the height of the epidemic, will have better survival rates, he says.

Some of the differences can be attributed to how the different studies were conducted, researchers say. For example, differences in the reliability of antibody tests used in the different studies, how COVID-19 deaths were recorded, and how researchers chose to divide populations by age.

There is some uncertainty in the data, so the estimates between studies may not be as different as they may seem, says Lucy Okell, an epidemiologist at Imperial College London, who was involved in the English study.

But a major factor in the various reported death rates between countries seems to be whether the virus is spreading in nursing homes as facilities for elderly care, says Salje.

In these places, people in fragile health live in close environments where the virus can spread rapidly. When the English study took into account deaths for care homes, the IFR in people aged 75 or older jumped from 11.6% to 18.7%. Sales estimates that the IFR for Canada, where about 85% of deaths occurred in nursing homes, would be significantly higher than that for Singapore, where nursing homes accounted for only 8% of deaths.

Although estimates of deaths are important for understanding the risk of viral spread to people in different age groups, they do not tell the full story of the toll COVID-19 takes, Kilpatrick says. “There is a fascination with death, but COVID-19 appears to be a substantial amount of disease in the long run,” he adds.