Kidney Decline Faster After Severe COVID vs Other Pneumonia

COVID-19 infection may be harder on the kidneys than other respiratory tract infections, a Swedish observational study indicated.

Comparing the change in estimated glomerular filtration rate (eGFR) before and after COVID, individuals had a mean eGFR decline that was 5.0 mL/min/1.73 m² faster after infection in hospitalized cases and 3.2 mL/min/1.73 m² faster among nonhospitalized cases.

In a prepandemic cohort of patients with pneumonia from the flu or other respiratory tract infections, mean eGFR declines were 2.4 mL/min/1.73 m² faster among hospitalized cases compared with pre-infection slopes, while there was no significant difference in the change among the nonhospitalized subset, reported researchers led by Viyaasan Mahalingasivam, MPhil, of the London School of Hygiene & Tropical Medicine.

“In this cohort study, we found accelerated kidney function decline after severe COVID-19 that was of greater magnitude than after other causes of pneumonia,” the authors wrote in JAMA Network Open. “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 [CKD] to effectively prevent complications and further decline.”

After adjustment, mean annual eGFR decline was 3.4% (95% CI 3.2-3.5) postinfection for the COVID cases overall, increasing to 5.4% (95% CI 5.2-5.6) among the hospitalized subset. For the pneumonia cases overall, the mean annual eGFR decline was 2.3% (95% CI 2.1-2.5), which stayed similar for those requiring hospitalization.

A 25% reduction in eGFR was significantly more likely among patients with COVID compared with other pneumonias (HR 1.19, 95% CI 1.07-1.34), driven almost entirely by the subset hospitalized for COVID (HR 1.42, 95% CI 1.22-1.64).

Mahalingasivam’s team posited that acute kidney injury (AKI), which occurs in roughly 30% of COVID-19 hospitalizations, could explain some of the acceleration in eGFR decline. In this study, 19% of those hospitalized with COVID-19 and 22.7% hospitalized with pneumonia had concurrent AKI.

Prior research has also suggested that COVID-related AKI puts patients at higher risk for subsequently developing CKD versus bacterial pneumonia.

Another potential explanation could be the reduced healthcare resources during the pandemic, Mahalingasivam and co-authors suggested.

For their analysis, researchers relied on health record data from the Stockholm Creatinine Measurements (SCREAM) Project. Included individuals — both hospitalized and nonhospitalized adults — had to have at least one eGFR measurement in the 2 years prior to their COVID or pneumonia diagnosis.

The pandemic-era group included 134,565 patients testing positive for COVID-19 from February 2020 to January 2022 (during which the dominant variants in Sweden were wild-type, Alpha, and Delta), while the pre-pandemic cohort included 35,987 patients with pneumonia from February 2018 to January 2020.

“We chose pneumonia as a comparator given that pneumonia is the predominant indication for COVID-19 hospitalization, and we chose a period prior to the pandemic to avoid misclassification,” the researchers explained.

The COVID group was younger (median 51 vs 71 years), had a similar proportion of women (56% vs 54%), and were less likely to require hospitalization (13% vs 47%). At baseline, median eGFR in the two groups was 94 and 79 mL/min/1.73 m², respectively.

The median number of creatinine tests available to estimate postinfection slopes was two for both groups. But generally, patients who had postinfection eGFR measurements tended to be older and had more comorbidities than those without postinfection eGFR measurements.

Models were adjusted for multiple factors: age, sex, annual income, educational level, diabetes, hypertension, cardiovascular diseases, non-hematological cancer, immunosuppressed diseases, AKI, previous pneumonia, number of hospital admissions in the preceding 5 years, and renin-angiotensin system inhibitor use in the preceding 6 months.

“Because our study concluded in January 2022, we had insufficient follow-up after healthcare services had recovered, and we recommend investigation over a longer period,” the researchers said. Some of the other study limitations included a lack of information on ethnicity and BMI as potential confounders.

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