Objective
To examine the relationship between the poverty and education levels and 24-hour urine
composition in patients with nephrolithiasis because little is known about the relationship
between socioeconomic status and kidney stone risk.
Methods
A retrospective review was performed of patients evaluated at 2 metabolic stone clinics.
The poverty level (ie, percentage of those living below the poverty level) and education
level (ie, percentage of those with a high school education or greater) for each postal
code were determined from the U.S. Census Bureau data. Multivariate linear regression
analysis was used to examine the relationship between the poverty and education levels
and 24-hour urine composition.
Results
A total of 435 patients were included in the present study. Of the 435 patients, 173
were women and 262 were men (40% women), the mean age was 52.5 ± 14.4 years, and the
mean body mass index was 28.6 ± 6.5 kg/m2. The mean percentage of those below the poverty level was 8.2% ± 6.2%, and the mean
percentage of those with a high school education or greater was 87.4% ± 7.4%. On multivariate
linear regression analysis, an increasing local poverty level was associated with
significant increases in urine calcium (β = 1.51, 95% confidence interval [CI] 0.16-2.86).
A decreasing local level of education (ie, decreasing percentage of those with a high
school diploma or greater) was associated with significant increases in urine calcium
(β = 1.26, 95% CI 0.10-2.42), supersaturation of calcium oxalate (β = 0.04, 95% CI
0.006-0.09), and supersaturation of calcium phosphate (β = 0.013, 95% CI 0.0002-0.03).
No other associations were found between the poverty and education levels and any
urine constituents or supersaturations.
Conclusion
In the present study of patients with stone formation, increasing poverty was associated
with increased urine calcium, and increasing education appeared to be protective by
decreasing urine calcium and the supersaturation of calcium oxalate and calcium phosphate.
Additional studies are important to elucidate the mechanisms underlying these findings.
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Article info
Publication history
Published online: May 21, 2012
Accepted:
December 12,
2011
Received:
October 11,
2011
Footnotes
Financial Disclosure: The authors declare that they have no relevant financial interests.
Identification
Copyright
© 2012 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
