Abstract
BackgroundDemographics influence kidney stone risk and the type of stone that is more likely to form. Common kidney stone risk factors include having a low urine volume and a high urine concentration. The goal of the current study was to evaluate the effect of demographics on urinary concentration and osmole excretion.MethodsTwenty-four-hour urine samples were collected from non-Hispanic white sibships in Rochester, MN. Height, weight, blood pressure, serum creatinine, and cystatin C were measured. Diet was assessed using the Viocare food frequency questionnaire. Effects of demographics and dietary elements on urine osmolality and volume were evaluated in bivariate and multivariable models, as well as models that included dietary interactions with age, sex, and weight.ResultsSamples were available from 709 individuals (mean age 66 ± 9 years, 59 % female). Across the age spectrum, males had higher urine osmolality (~140 mOsm/kg, p < 0.0001) and total osmole excretion (~270 mOsm, p < 0.0001) compared to females. For any given urine volume, males had a consistently higher urine osmolality (~140 mOsm/kg, p < 0.0001). In multivariable models, urine osmolality declined with age and water intake and remained higher in males than females. Urine osmolality positively associated with weight and animal protein intake. Higher urine volume associated with larger water intake. An interaction revealed that greater body weight was associated with larger changes in urine osmolality as oxalate intake increased (p = 0.04).ConclusionData from this study support the hypothesis that there are sex differences in thirst and vasopressin action. This trend in urine concentration is also consistent with known epidemiologic patterns of urinary stone disease risk.Electronic supplementary materialThe online version of this article (doi:10.1186/s13293-016-0063-0) contains supplementary material, which is available to authorized users.
Highlights
Demographics influence kidney stone risk and the type of stone that is more likely to form
GENOA cohort The multi-phase Genetic Epidemiology Network of Arteriopathy (GENOA), a member of the Family Blood Pressure Program (FBPP), recruited non-Hispanic white hypertensive sibships from Rochester, Minnesota (MN), for linkage and association studies to investigate the genetic underpinnings of hypertension in phase I (1996– 2001) [8]
Recruitment for the original GENOA study and the current Genetic Determinants of Urinary Lithogenicity (GDUL) ancillary study was not based on chronic kidney disease (CKD) status or on the presence of urinary stones
Summary
Demographics influence kidney stone risk and the type of stone that is more likely to form. Common kidney stone risk factors include having a low urine volume and a high urine concentration. The goal of the current study was to evaluate the effect of demographics on urinary concentration and osmole excretion. Human urine is almost always supersaturated for one or more crystal types that can form stones (i.e., calcium oxalate, calcium phosphate, and uric acid). High fluid intake has been universally advocated for stone prevention in order to favor more dilute urine. Association (AUA) and American College of Physicians (ACP) both recommend sufficient fluid intake to maintain urine volume of 2.0 to 2.5 L [2, 3]. Urine osmolality and volume are relevant factors to assess in the context of kidney stone risk
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