Twenty-four-Year Trends in Incidence and Mortality of Nephrotic Syndrome: A Population-Based Cohort Study

Background: With the increasing prevalence of risk factors for nephrotic syndrome, updated epidemiologic data on the syndrome are needed. We examined its age- and sex-specific incidence, histopathology, and mortality over 24 years. Methods: This nationwide cohort study included all adults with first-time-recorded nephrotic syndrome in Denmark during 1995–2018 using the Danish National Patient Registry. We obtained data on age, sex, hospital-diagnosed comorbidities, and histopathologic findings. We computed overall, and age- and sex-specific, incidence rates of nephrotic syndrome, 1- and 5-year mortality by calendar period, and 1-year hazard ratios (HRs) of death using Cox models. Results: We identified 3,970 adults with first-time nephrotic syndrome diagnosis. Incidence was highest in men and increased with age to 11.77 per 100,000 person-years (95% confidence interval [CI]: 10.21–13.32) in men aged 80+ years, and 6.56 per 100,000 person-years (95% CI: 5.71–7.41) in women aged 80+ years. Incidence of nephrotic syndrome increased from 3.35 per 100,000 person-years (95% CI: 3.12–3.58) in 1995–2000 to 4.30 per 100,000 person-years (95% CI: 4.05–4.54) in 2013–2018. Over time, 1-year mortality of nephrotic syndrome was stable at 13%–16%, but HR of death was 0.54 (95% CI: 0.42–0.69), adjusted for age, sex, and comorbidities, in 2013–2018 compared with 1995–2000. Subdistribution of glomerulopathies was stable over time with membranous nephropathy and minimal change disease being the most common. Conclusion: During 1995–2018, the incidence of recorded adult nephrotic syndrome increased slightly, and the adjusted mortality of nephrotic syndrome decreased markedly. Whether these findings reflect changes in epidemiology or awareness and coding of nephrotic syndrome, remains to be clarified.