People with age-related macular degeneration – an eye disorder caused by overactive immune system — are at greater risk of developing severe complications and dying from COVID-19, according to a study.

Complement, one of the immune system’s oldest branches may be influencing the severity of COVID-19 disease, said the researchers at Columbia University in the US.

The findings, published in the journal Nature Medicine, suggest that existing drugs that inhibit the complement system could help treat patients with severe disease.

The researchers also found evidence that clotting activity is linked to COVID-19 severity and that mutations in certain complement and coagulation genes are associated with hospitalisation of COVID patients.

“Together these results provide important insights into the pathophysiology of COVID-19 and paint a picture for the role of complement and coagulation pathways in determining clinical outcomes of patients infected with SARS-CoV-2,” said Sagi Shapira, who led the study with Nicholas Tatonetti, both professors at Columbia University.

If complement and coagulation influence severity of COVID-19, people with pre-existing hyperactive complement or coagulation disorders should be more susceptible to the virus, the researchers said.

That led researchers to look at COVID-19 patients with macular degeneration, an eye disease caused by overactive complement, as well as common coagulation disorders like thrombosis and hemorrhage.

Among 11,000 patients who came to Columbia University Irving Medical Center with suspected COVID-19, the researchers found that over 25 per cent of those with age-related macular degeneration died, compared to the average mortality rate of 8.5 per cent, and roughly 20 per cent required intubation.

The greater mortality and intubation rates could not be explained by differences in the age or sex of the patients, the researchers said.

“Complement is also more active in obesity and diabetes and may help explain, at least in part, why people with those conditions also have a greater mortality risk from COVID,” Shapira said.

People with a history of coagulation disorders also were at increased risk of dying from COVID 19 infection, the researchers added.

(This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.)

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