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COVID-19 was linked to a faster annual decline in kidney function than pneumonia, prompting study authors to call for closer kidney monitoring.

Patients experienced a greater annual decline in kidney function after COVID-19 infection compared with after pneumonia due to other infections, according to a study published in JAMA Network Open.

Researchers found that the magnitude of accelerated kidney function decline was steepest in patients hospitalized for COVID-19.

“We, therefore, propose that people who were hospitalized for COVID-19 receive closer monitoring of kidney function to ensure prompt diagnosis and optimized management of chronic kidney disease to effectively prevent complications and further decline,” wrote corresponding author Viyaasan Mahalingasivam, MPhil, and colleagues.

Investigators assessed links between COVID-19 infection and long-term kidney function in light of known associations between COVID-19 and acute kidney injury. Nearly a third of COVID-19 hospitalizations, the researchers noted, have involved acute kidney injury.

“Besides the differences in settings, definitions, and duration of follow-up, a common limitation of prior studies has been the lack of consideration of preexisting kidney function trajectory,” they wrote, “which may explain both postinfection decline and the need for function monitoring.”

The current study used linked health record data from the Stockholm Creatinine Measurements Project in Stockholm, Sweden. The researchers compared estimated glomerular filtration rate (eGFR) measurements before and after a COVID-19 positive test result or pneumonia diagnosis in hospitalized and non-hospitalized adult patients.

The study included 134,565 adults with COVID-19, who had a median age of 51 years and a median baseline eGFR of 94 mL/min/1.73m². For the 35,987 adults with pneumonia also included in the analysis, the median age was 71 years and the median baseline eGFR was 79 mL/min/1.73m².

The magnitude of eGFR decline, the researchers discovered, was greater for survivors of COVID-19 than survivors of pneumonia over a median of 10.8 months of follow-up. Adjusted rates of annual eGFR decline were 3.4% after COVID-19 compared with 2.3% after pneumonia, according to the study.

“This decline was more severe among individuals hospitalized for COVID-19 (5.4%; 95% CI, 5.2%-5.6%),” the researchers reported, “but remained similar among those hospitalized for pneumonia.”

Acute kidney injury experienced during hospitalization for COVID-19 could explain the subsequent decline in eGFR, the researchers wrote, but such investigation was beyond the study’s scope.

“Generalizing these findings should be done with caution,” the researchers wrote. “We recommend triangulation with similar analyses in other healthcare systems and longer follow-up.”