Temperature Effects on the Hydration Status

Abstract

ISEE-0591 Background and Objective: Extreme hot or cold temperature was found to be related with cause-specific morbidity and mortality in previous studies, but few studies examined the pathway of temperature-related health. In the present study, we hypothesized that with temperature changes below or above the threshold level, higher concentrations of BUN/Creatinine ratio and urine specific gravity were produced as a result of keeping the adequate hydration status. Methods: The generalized linear models (GLM) were used to examine the association between the temperature and the hydration status after controlling for gender, age, and season. Blood chemistry data for 44,442 individuals were collected from Seoul National University Hospital, Seoul, Korea, based on the physical examinations occurred between May 1, 1995 and December 31, 2006 in Seoul. Meteorological data on temperature were acquired from the Korea Meteorological Administration (KMA). Akaike's information criterion (AIC) value was used to estimate the threshold of temperature where the effects of temperature on the hydration status were the lowest. Results: V-shape associations between the temperature and the hydration status were found. The threshold temperature levels were 21.6°C and 22.2°C for BUN/Creatinine ratio and urine specific gravity, respectively. BUN/Creatinine level decreased as temperature increased from the coldest days to the threshold temperature (β = −0.03059, P-value = 1.42E-10) and increased above the threshold temperature (β = 0.091998, P-value = 3.78E-07). Similarly, the urine specific gravity level decreased below the threshold temperature (β = −7.68E-05, P-value = 8.18E-36) and increased above the threshold temperature (β = 0.0001866, P-value = 1.22E-13). Conclusion: The study provided the evidence of temperature effects on the hydration status and may suggest a pathway of temperature-related health outcomes under the extreme weather conditions.