Premature mortality due to nephrotic syndrome and the trend in nephrotic syndrome mortality in Japan, 1995–2014

Minako Wakasugi, Junichiro James Kazama, Ichiei Narita

This study analysed the trend in mortality from nephrotic syndrome in Japan from 1995 to 2013. Moreover, to better understand premature death from nephrotic syndrome, the average years of life lost due to nephrotic syndrome were estimated. National death certificate data were evaluated. Age-standardised mortality rates from nephrotic syndrome were calculated by direct standardisation using the World Standard Population. Trends for average annual changes in percentages were determined by joinpoint regression analysis. Average years of life lost were estimated by dividing total years of life lost by the number of deaths from nephrotic syndrome. Years of life lost were estimated by the constant end-point method, with 65 years as the endpoint. Average years of life lost due to malignant neoplasms, the leading cause of death in Japan, were estimated for comparison. There were 9945 deaths (4872 men and 5073 women) during the study period. The numbers of deaths and crude overall mortality rates increased, while age-standardised mortality rates continuously decreased, for both sexes. The annual percentage changes were -1.9% [95% confidence interval (CI), -2.3 to -1.4%] for men and -3.5% (95% CI -4.1 to -2.9%) for women. The average years of life lost due to nephrotic syndrome decreased during the study period, but were greater than for patients who died of malignant neoplasm. Mortality and premature mortality rates from nephrotic syndrome significantly decreased in Japan between 1995 and 2014. Despite these improvements, nephrotic syndrome patients ≤65 years of age still have a poor prognosis.