For the study, the researchers examined the health records of 12,971 individuals who were tested for Covid-19 within the Geisinger Health System in the US.

Of this group, 1,604 were Covid-positive and 354 required hospitalisation.

The team analysed the records for association between specific clinical conditions, including kidney, cardiovascular, respiratory and metabolic conditions, and Covid-19 hospitalisation.

Overall, chronic kidney disease was most strongly associated with hospitalisation, and COVID-19 patients with end-stage renal disease were 11 times more likely to be admitted to the hospital than patients without kidney disease,  said the study published in the journal PLOS ONE.

"Previous studies have identified a variety of health conditions associated with an increased risk of COVID-related hospitalisation, including diabetes, heart failure, hypertension, and chronic kidney disease," said Alex Chang,  Geisinger nephrologist and co-director of Geisinger's Kidney Health Research Institute.

"What is significant here is the magnitude of the kidney disease-related risk."

How underlying medical conditions increase the risk of Covid-19-related complications is not yet fully clear.

However, the study suggests that the physiological stress caused by an excessive inflammatory response to Covid-19 infection could destabilise organs already weakened by chronic disease, or that organ injury from the virus could  act as a "second-hit" to these organs.

"Consistent with this hypothesis, kidney and heart are among the tissues with the highest expression of ACE2, a SARS-CoV-2 receptor," the team wrote.