Why COVID-19 is more severe in older people than young decoded

Scientists in the US have found a possible explanation for the severe lung complications seen in some people diagnosed with COVID-19, pointing out the role of medications recommended for patients with heart attacks, high blood pressure, diabetes and chronic kidney disease.

In a study published in the Journal of Travel Medicine, the researchers note that the SARS beta coronaviruses, such as the new SARS-CoV-2, which causes COVID-19, bind to angiotensin converting enzyme 2 (ACE2) receptors in the lower respiratory tracts of infected patients to gain entry into the lungs.

Viral pneumonia and potentially fatal respiratory failure may result in susceptible persons after 10-14 days, they said.

"Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are highly recommended medications for patients with cardiovascular diseases including heart attacks, high blood pressure, diabetes and chronic kidney disease to name a few," said James Diaz, a professor at the Louisiana State University (LSU) in the US.

"Many of those who develop these diseases are older adults. They are prescribed these medications and take them every day," Diaz said.

Research in experimental models has shown an increase in the number of ACE2 receptors in the blood circulation between the heart and the lungs, after ACE inhibitors are injected into the veins, the scientists explained.

"Since patients treated with ACEIs and ARBS will have increased numbers of ACE2 receptors in their lungs for coronavirus S proteins to bind to, they may be at an increased risk of severe disease outcomes due to SARS-CoV-2 infections," said Diaz.

This hypothesis, he said, is supported by a recent analysis of 1,099 patients with laboratory-confirmed COVID-19 infections treated in China during the reporting period, December 11, 2019, to January 29, 2020.

This study reported more severe disease outcomes in patients with hypertension, coronary artery disease, diabetes and chronic renal disease.

All patients with the diagnoses met the recommended indications for treatment with ACEIs or ARBs, according to the researchers.

Diaz said that two mechanisms may protect children from COVID-19 infections -- cross-protective antibodies from multiple upper respiratory tract infections caused by the common cold-causing alpha coronaviruses, and fewer ACE2 receptors in their lower respiratory tracts to attract the binding S proteins of the beta coronaviruses.

He recommends future case-control studies in patients with COVID-19 infections to further confirm chronic therapy with ACEIs or ARBs may raise the risk for severe outcomes.

"Patients treated with ACEIs and ARBs for cardiovascular diseases should not stop taking their medicine, but should avoid crowds, mass events, ocean cruises, prolonged air travel, and all persons with respiratory illnesses during the current COVID-19 outbreak in order to reduce their risks of infection," he added.