People who have long COVID – and especially those who were hospitalized from the virus or have diabetes – show a significant decline in kidney function in the 12 months following infection, a study reveals. The results suggest these patients may be at higher risk of developing chronic kidney disease later on in life and should be monitored closely.
Dr. Peter Birks is a nephrologist with Fraser Health who helped oversee the implementation of post-COVID recovery clinics in BC. “We were in a unique situation to be following a lot of these patients over time and to assess those long-term effects of COVID,” explains Birks. “There were a lot of interesting findings.”
In their study, Birks’ team analyzed data capturing 2,212 long COVID patients 18 years of age and older who were referred to the post-COVID recovery clinics between July 2020 and April 2022. All patients included in the study had their kidney function measured within three months of COVID infection, using eGFR (estimated glomerular filtration rate), and at different intervals following diagnosis (e.g., six months, 12 months).
The results reveal that long COVID patients experienced an estimated 2.96 mL/min decrease in eGFR (3.39% reduction from baseline) one year after COVID infection. While everyone naturally loses some kidney function over time, in healthy people a 1 mL/min decline over such a time period is more typical. Decline in kidney function was highest in patients hospitalized for COVID-19, at 6.72%, followed by diabetic patients, at 6.15%.
“Most long COVID patients in this study did not develop advanced kidney disease – less than 5% had a GFR less than 30 across all of the timepoints – but certainly more of them fit into the ‘less than normal’ GFR category,” says Birks. Kidney failure is measured by an eGFR of less than 15, severe kidney damage by an eGFR of 15-30, moderate, 30-59, and mild, 60-89.
More than a third of patients (36%) were also found to have protein in the urine at some point in their follow up, which is another indicator of kidney disease. Based on these findings, Birks recommends that anyone who has long COVID, who was hospitalized from COVID-19 and/or who has diabetes, is closely monitored for kidney disease following a COVID-19 infection.
Birks says he plans to continue to study the effects of COVID-19 on the kidneys, including in people who already had kidney disease prior to a COVID-19 infection. His team is also working to develop tools for outpatient management and screening following episodes of sudden kidney function decline (called acute kidney injury or AKI). “We’re looking to optimize things like discharge summaries, patient education handouts and resources for family physicians regarding AKI,” he says.