INTRODUCTION: Increases in ambient temperature have recently been associated with increased risk of hospital admission for a number of kidney pathologies. However, how increased temperature might affect renal pathophysiology has not yet been elucidated. METHODS: Multiple regression models evaluated the association between 1- and 3-day average, ambient temperature levels and biomarkers of kidney injury (neutrophil gelatinase-associated lipocalin (NGAL) and adiponectin), among 3,377 individuals over 57 years of age enrolled in the National Social Life, Health, and Aging Project. Mediation of the affects of temperature through blood pressure was also explored. Temperature estimates were based upon data from the National Climatic Data Center (NCDC) and spatially smoothed on a six-kilometer grid covering the U.S.. Models were adjusted for demographic, socioeconomic, health behavior, medical history variables, and ambient particulate matter. RESULTS: Individuals in the top quartile of daily temperature (>200C) had 16.10% (SE 5.70%, p=0.008) higher levels of NGAL and 28.03% (SE 6.35%, P<0.001) higher levels of adiponectin relative to those in the lower quartiles. Associations for 3-day average exposures were attenuated (NGAL: 9.90%, SE 5.61, p=0.086; Adiponectin: 20.96%, SE 6.28%, p=0.002). Spline curves of continuous temperature exposures identified significant non-linearity, with non-significant associations for ambient temperatures <100 C, and significant, linear effects for ambient temperatures >100C. In models restricted to exposures >100C, each 10C increase was associated with 1.98% (SE 0.58, p<0.001) higher NGAL and 2.77% (SE 0.63, p<0.001) higher adiponectin levels. Significant mediation was not identified. CONCLUSIONS: In a cohort of older Americans, daily ambient temperature exposures were significantly associated with biomarkers of acute renal injury. These associations suggest that ambient temperature exposures may be an important risk factor for acute kidney injury.
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