Older People's Noses May Make Them More Vulnerable to Catching Coronavirus

While children can catch the coronavirus which causes COVID-19, they appear less susceptible to severe cases than adults. Now, scientists believe this may have to do with the structure of the inside of their noses.

In the cells which line this part of the body, children appear to produce fewer of the proteins which SARS-CoV-2 (the coronavirus which causes COVID-19) uses to invade our body. According to the authors of a research letter published in the journal JAMA, we appear to create more of the protein which SARS-CoV-2 uses as a receptor—an enzyme called ACE2—as we age.

The team at Icahn School of Medicine at Mount Sinai looked at samples of the nasal epithelium from 305 people aged four to 60-years-old. Participants provided the samples at Mount Sinai Health System between 2015 and 2018 for a study on asthma.

But the authors of the JAMA study decided they would also be useful for checking the levels at which the gene that produces ACE2 is expressed in different age groups. Participants were categorized to reflect the developmental stages of life: children under 10, children aged 10 to 17, young adults aged 18 to 24, and adults at 25 and over. A total of 48.9 percent of the volunteers were male, and 49.9 percent had asthma.

The expression of the ACE2 gene was lowest in younger children, and significantly higher in the other groups, rising with age. To ensure sex and asthma didn't create biased results, they adjusted for these factors and still made the same findings.

"The results from this study show age-dependent expression of ACE2 in nasal epithelium, the first point of contact for SARS-CoV-2 and the human body," the authors wrote. "Lower ACE2 expression in children relative to adults may help explain why COVID-19 is less prevalent in children."

However, they acknowledged the study was limited because the sample did not include people aged over 60. This age group is known to be vulnerable to complications of COVID-19.

Not many studies have looked at the potential link between ACE2 in airways and age, the authors explained. One study involving 92 patients with acute respiratory distress syndrome found no such link, but that team looked for the activity of the ACE2 protein rather than gene expression, which the authors of the JAMA study said may explain the differences in their findings.

In an editorial accompanying the research letter also published by JAMA, Dr. Ankit B. Patel and Ashish Verma of the Brigham and Women's Hospital Renal Division explained it is unclear whether rates of SARS-CoV-2 in children appear low because they are less likely to be sick enough to need testing and be included in data, or because they are less susceptible to infection. Studies on the topic have had conflicting results: one showing children are as likely to catch it as middle-aged adults, and others finding lower incidence in this age group.

Patel and Verma said studying the expression of ACE2 in the lower respiratory tract of children "may be helpful in understanding differences in the severity of COVID-19 among children compared with adults." A new study called Human Epidemiology and Response to SARS-CoV-2 (HEROS) involving 6,000 children to examine the risk factors of COVID-19 could help build on these findings, they said.

Five months into the COVID-19 pandemic, the total number of confirmed cases has hit 5 million, according to Johns Hopkins University. More than 328,172 people have died, and over 1.8 million have recovered. As the map below by Statista shows, the U.S. is the country with the most known cases. This week, Brazil overtook the U.K. as the country with the third most known cases.

covid countries may 20
This graphic shows the ten countries with the highest number of coronavirus cases as of May 20. Statista