Proteinuria and life expectancy.

To the Editor: Proteinuria, a marker of kidney disease, is associated strongly with risk of adverse outcomes, including all-cause mortality. Life expectancy, a measure to estimate health status and disease burden at a population level, has not been reported for patients with different levels of proteinuria. This information could help policy makers recognize the health burden caused by proteinuria and prioritize health care programs or funding. We used a large population-based registry to estimate life expectancies of middle-aged men and women with varying levels of proteinuria. The study population included adults without end-stage renal disease in Alberta, Canada, who had at least one outpatient to identify all-cause mortality. Baseline proteinuria was estimated by urine albu-min-creatinine ratio (ACR) or urine dipstick based on outpatient random spot urine measurements and categorized based on ACR (normal, Ͻ30 mg/g; mild, 30-300 mg/g; and heavy, Ͼ300 mg/g) or urine dipstick (normal, negative; mild, trace or 1ϩ; and heavy, 2ϩ). 4,5 Age-specific mortality rates were calculated with the person-year method, 6 where age was considered in time scale. The abridged life table was used to calculate life expectancies. (Details of the study methods have been published elsewhere 9 and are provided in Item S1). Among men, 9.55% had mild proteinuria and 2.03% had heavy proteinuria. Corresponding proportions among women were 7.48% and 1.22%, respectively. Figure 1 shows mean life expectancy for participants by sex and level of proteinuria in 5-year age bands (from 30 to Ն85 years). Within each age stratum, life expectancy was substantially shorter for people with higher levels of proteinuria (Table S1). Life expectancy for men aged 40 years was 31.8 years for those without proteinuria, 23.2 years for those with mild proteinuria, and 16.6 years for those with heavy proteinuria. Life expectancies for women aged 40 years with normal, mild, and heavy proteinuria were 35.7, 25.2, and 18.2 years, respectively. Life expectancies of 40-year-old men and women with no proteinuria were 15.2 and 17.4 years longer, respectively, than for those with heavy proteinuria (Table 1). Life expectancy was shorter in the presence of mild and heavy proteinuria (compared with those with no proteinuria) across all age strata for both sexes. Life expectancy for men was consistently shorter than for women for all proteinuria categories, especially in the middle age strata (Table S2). These results mirror our recent report of the life expectancy of patients across different levels of estimated glomerular filtration rate, …