Countering reports that older people are more likely to contract COVID-19, researchers found that advanced age does not increase susceptibility to SARS-CoV-2 infection.
However, when older people in Spain, Italy, and Japan did get COVID-19, they were at higher risk for severe outcomes and death compared with younger patients, new evidence reveals.
Although people 70 years and older were not more susceptible to infection versus younger counterparts, “our analysis suggests that the rates for becoming symptomatic, severe disease and death depend on age,” lead author Ryosuke Omori, PhD, told Medscape Medical News.
“This research suggests older adults have similar risk as younger adults to become infected with SARS-CoV-2,” Camille Vaughan, MD, told Medscape Medical News when asked to comment.
More research, such as active wide-scale epidemiologic surveillance, “is needed to accurately understand how different age groups have been impacted by COVID-19,” added Vaughan, who is an associate professor of medicine and division director of geriatrics and gerontology at Emory University School of Medicine in Atlanta, Georgia.
The findings reinforce the need for personal protection measures, particularly among younger and asymptomatic people. “We need to take care when all of us, at any age, have contact with elderly persons. We need to be careful to avoid a silent spread,” Omori, associate professor in the Research Center for Zoonosis Control at Hokkaido University in Japan, stated in an email.
The study was published online October 6 in Scientific Reports.
Omori and colleagues studied three countries with reliable COVID-19 data to understand why most deaths are among elderly people.
The number of confirmed COVID-19 cases per capita varied greatly by age among the three countries studied: 507 cases per 100,000 in Spain, 382 cases per 100,000 in Italy, and 13 cases per 100,000 in Japan. But all three countries experienced similar proportions of higher mortality linked to COVID-19 in older residents (although the actual numbers varied widely).
At the time of the study, Italy reported 29,525 deaths, Spain 28,828, and Japan 400.
Omori and colleagues developed a mathematical model to calculate COVID-19 susceptibility by age group, including social contacts and activities outside the home. The model showed that age was not associated with susceptibility to the disease.
They did find an elevated risk for severe outcomes, which makes sense, the researchers note, “because elder age as well as the existence of comorbidities, which are likely with aging, have been reported as risk factors for severe COVID-19 infections.”
“Although we cannot fully reject the existence of age-dependency in susceptibility,” the researchers note, “our results suggest that it does not largely depend on age, but rather that age-dependency in severity highly contributes to the formation of the observed age distribution in mortality.”
Further study of the interaction between age and more severe disease are warranted, Omori said. “We need to understand the mechanism for the age dependency of severity to reduce the number of severe cases.”
Such research will require an accurate case fatality rate. This calculation is currently challenging because of changing testing rates for COVID-19, selection biases, and the delay between symptom onset and death.
“I think the information overall fits with what we see in our environment,” Anthony J. Perry, MD, told Medscape Medical News when asked to comment on the study.
Perry cited online COVID-19 case and mortality rates from the Illinois Department of Public Health, which shows very similar trends. For example, the number of cases by age reveals no “major difference in the older age groups between the proportion of older adults tested and the proportion of older adults confirmed to have COVID-19,” said Perry, associate professor of geriatric medicine at Rush University Medical Center in Chicago, Illinois.
In contrast, the mortality rate rises substantially with each increasing decade of life and is particularly elevated among people over age 70 and 80.
That is “pretty striking,” Perry said.
“I think that fits nicely with the thought that older adults aren’t more likely to get COVID-19 but are much more likely to get severely ill if they get it.” The most likely conclusion is that, rather than age, the bigger driver of becoming infected with the virus is precautions taken to prevent infection, he said.
The Japan Society for the Promotion of Science provided financial support to Omori and coauthor Yukihiko Nakata. Omori, Perry, and Vaughan have reported no relevant financial relationships.
Sci Rep. Published online October 6, 2020. Full text
Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and rheumatology. Follow Damian on Twitter @MedReporter.