Covid-19 has been associated with an increased risk of a variety of disorders, including cardiovascular disease, clotting disorders, diabetes, chronic fatigue syndrome, and mood disorders. Influenza, another respiratory viral illness, is associated with long-term respiratory issues and an increased risk of hospitalisation. The comparative impact of each of these diseases on kidney health in the general population is not yet known. Therefore, researchers at the Penn State College of Medicine sought to determine the effects of Covid-19 and influenza on the risk of acute and chronic kidney disease.
For this retrospective cohort study, Yue Zhang and colleagues utilised the MarketScan database, which comprises 275 million Americans aged 18–64 years. The study spanned from January 2020 to December 2021. The three groups being studied were a group of Covid-19 cases (939,241 patients), a positive control group with influenza but not Covid-19 (199,071 patients), and a negative control group of neither Covid-19 nor influenza (1,878,482 cases). Outcomes included any renal disease, acute kidney injury (AKI), chronic kidney disease (CKD), or end-stage renal disease (ESRD).
Go deeper with GlobalData
Access deeper industry intelligence
Experience unmatched clarity with a single platform that combines unique data, AI, and human expertise.
When compared to the influenza group and negative control group, the Covid-19 group exhibited the highest incidence of AKI (8.93 cases per 100,000 person-years), CKD (6.36 cases per 100,000 person-years), and ESRD (0.64 cases per 100,000 person-years). Covid-19 patients were also at higher risk than influenza patients for any kidney disease (Covid-19 hazard ratio [HR] 1.93, influenza HR 1.10), AKI (Covid-19 HR 2.74, influenza HR 1.24), CKD (Covid-19 HR 1.38, influenza HR 1.03), and ESRD (Covid-19 HR 3.22, influenza HR 0.84). Notably, the influenza patients did not have a significantly increased risk for either CKD or ESRD while the Covid-19 patients experienced increased risk of all outcomes.
The authors also followed a subset of the original cohort for up to 540 days. This cohort contained 561 Covid-19 cases, 864 negative controls, and 184 influenza cases. The study demonstrated that contraction of either Covid-19 or influenza increased the risk of AKI over the follow-up period. Notably, within the first 180 days, Covid-19 conferred a higher risk of AKI (HR 4.35, 95% confidence interval [CI]: 4.09–4.63) than influenza (HR 1.51, 95% CI: 1.29–1.78). This declined for both diseases by 540 days. The impact on CKD was consistent for both diseases throughout the follow-up period. Specifically, Covid-19 conferred a significantly increased risk of CKD (HR 1.4) while influenza did not.
The findings of this study have implications for long-term post-Covid-19 care. Significantly increased risk of AKI demands heightened monitoring for kidney disease development in Covid-19 patients shortly after infection.
This extends to long-term surveillance for CKD. In the US in 2026, GlobalData epidemiologists forecast that there will be over 2.2 million diagnosed incident cases of AKI, 5.3 million diagnosed prevalent cases of CKD, and over 750,000 diagnosed prevalent cases of ESRD. While it is still difficult to determine how many of these cases are attributable to Covid-19, it may be worth treating the viral illness as a potential risk factor in the future.
