Age-related decline in urine concentration may not be universal: Comparative study from the US and two small-scale societies

• Type of Material: Article
• Authors: Asher Y. Rosinger, Pennsylvania State University; Herman Pontzer, Duke University; David A. Raichlen, University of Arizona; Brian M. Wood, University of California Los Angeles; Susan N. Tanner, University of Georgia; Jeff Sands, Emory University
• Language: English
• Date: 2019-04-01
• Publisher: Wiley Inc.
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2019 Wiley Periodicals, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1002/ajpa.23788
• Title of Journal or Parent Work: American Journal of Physical Anthropology
• Volume: 168
• Issue: 4
• Start Page: 705
• End Page: 716
• Grant/Funding Information: Grant sponsorship: This work was supported by funding from the Wenner-Gren Foundation #8718 (AR), National Science Foundation #1341161 (AR), NSF-BCS-0850815 (HP), NSF-BCS 1440867 (DAR), NSF-BCS 1440841 (HP), NSF-BCS 1440671 (BMW), and National Institutes of Health NIH R01 DK41707 (JS).
• Keywords: Anthropology; aging; Life Sciences & Biomedicine; RENAL-FUNCTION; KIDNEY-DISEASE; UNITED-STATES; kidney physiology; BLOOD-PRESSURE; DIETARY-PROTEIN; lifestyle mismatch; Evolutionary Biology; ABILITY; HEAT TOLERANCE; Science & Technology; urine concentration; WATER-DEPRIVATION; HYDRATION STATUS; TSIMANE ADULTS
• Research Categories: Health Sciences, Public Health; Anthropology, Medical and Forensic; Health Sciences, Medicine and Surgery

Abstract

Objectives: Evidence from industrialized populations suggests that urine concentrating ability declines with age. However, lifestyle factors including episodic protein intake and low hypertension may help explain differences between populations. Whether this age-related decline occurs among small-scale populations with active lifestyles and non-Western diets is unknown. We test the universality of age-related urine concentration decline. Materials and Methods: We used urine specific gravity (Usg) and urine osmolality (Uosm) data from 15,055 U.S. nonpregnant adults without kidney failure aged 18–80 in 2007–2012 participating in the National Health and Nutrition Examination Survey (NHANES). We tested the relationship of age on urine concentration biomarkers with multiple linear regressions using survey commands. We compared results to longitudinal data on Usg from 116 Tsimane’ forager-horticulturalists (266 observations) adults aged 18–83 in 2013–2014 from Lowland Bolivia, and to 38 Hadza hunter-gatherers (156 observations) aged 18–75 in 2010–2015 from Tanzania using random-effects panel linear regressions. Results: Among U.S. adults, age was significantly negatively associated with Usg (Adjusted beta [B] = −0.0009 g/mL/10 years; SE = 0.0001; p < 0.001) and Uosm (B = −28.1 mOsm/kg/10 yr; SE = 2.4; p < 0.001). In contrast, among Tsimane’ (B = 0.0003 g/mL/10 yr; SE = 0.0002; p = 0.16) and Hadza (B = −0.0004 g/mL/10 yr; SE = 0.0004; p = 0.29) age was not associated with Usg. Older Tsimane’ and Hadza exhibited similar within-individual variability in Usg equivalent to younger adults. Discussion: While U.S. adults exhibited age-related declines in urine concentration, Tsimane’ and Hadza adults did not exhibit the same statistical decline in Usg. Mismatches between evolved physiology and modern environments in lifestyle may affect kidney physiology and disease risk.