Sunday, April 21, 2013

Proteinuria Linked to Life Expectancy

Individuals with proteinuria may have a shorter estimated life expectancy compared with their healthier counterparts, a Canadian study showed.
Among 40-year-olds, for example, men and women with heavy proteinuria were expected to die 15.2 and 17.4 years earlier, respectively, than those without proteinuria, Tanvir Chowdhury Turin, MBBS, PhD, of the University of Calgary in Alberta, and colleagues reported in a research letter in theAmerican Journal of Kidney Diseases.
"These results mirror our recent report of the life expectancy of patients across different levels of estimated glomerular filtration rate, in which we observed that lower levels of kidney function were associated with a decrease in life expectancy for both men and women," they wrote. "This information could help policy makers recognize the health burden caused by proteinuria and prioritize healthcare programs or funding."
The data came from a population-based registry in Alberta. The analysis included 812,386 patients 30 and older who did not have end-stage renal disease, and who had at least one measurement for proteinuria between May 2002 and December 2006. They were followed through March 2009.
Proteinuria was assessed at baseline using urine albumin-creatinine ratio (ACR) or urine dipstick.
An ACR of less than 30 mg/g was considered normal, a value of 30 to 300 mg/g was mild, and a value of greater than 300 mg/g was heavy.
A negative dipstick reading was considered normal, with mild proteinuria indicated by a trace or 1+ reading and heavy proteinuria by a 2+ reading.
Proteinuria was mild in 9.55% of men and 7.48% of women and heavy in 2.03% of men and 1.22% of women.
Within each 5-year age group going up to 85 and for both sexes, life expectancy was shorter for individuals with higher levels of proteinuria. Men consistently had a shorter life expectancy compared with women.
For 40-year-0ld men, for example, life expectancy 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. The values for 40-year-old women were 35.7, 25.2, and 18.2 years across increasing levels of proteinuria.
The authors noted that the life expectancy for the middle-age population without proteinuria in their study was 7 or 8 years shorter than that seen in the general population of Alberta at the same time.
"This difference may be due to the selective nature of our cohort, including that it comprised individuals who had outpatient proteinuria measurements as part of routine care and excluded presumably healthier individuals who did not access medical services and receive proteinuria testing," they wrote. "This might have selected patients with comorbid conditions associated with kidney disease and increased the overall risk of mortality for the cohort."
Other limitations included the use of a single measurement of proteinuria at baseline, the lack of adjustment for comorbidities and kidney function, and the inability of the method for estimating life expectancy to account for changes in risk factors over time.
Turin is supported by Fellowship Awards from the Canadian Institutes of Health Research (CIHR), Canadian Diabetes Association, and the Interdisciplinary Chronic Disease Collaboration team grant funded by Alberta Innovates-Health Solutions (AI-HS). Turin's coauthors reported support from AI-HS, CIHR, the Roy and Vi Baay Chair in Kidney Research, a Canada Research Chair, and a KRESCENT new investigator award.
The authors reported no conflicts of interest.
Primary source: American Journal of Kidney Diseases
Source reference:
Turin T, et al "Proteinuria and life expectancy" Am J Kidney Dis 2013; DOI: 10.1053/j.ajkd.2012.11.030.

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