标题：Prevalence of Inadequate Hydration Among US Children and Disparities by Gender and Race/Ethnicity: National Health and Nutrition Examination Survey, 2009–2012
摘要：Objectives. We evaluated the hydration status of US children and adolescents. Methods. The sample included 4134 participants aged 6 to 19 years in the National Health and Nutrition Examination Survey from 2009 to 2012. We calculated mean urine osmolality and the proportion with inadequate hydration (urine osmolality > 800 mOsm/kg). We calculated multivariable regression models to estimate the associations between demographic factors, beverage intake, and hydration status. Results. The prevalence of inadequate hydration was 54.5%. Significantly higher urine osmolality was observed among boys (+92.0 mOsm/kg; 95% confidence interval [CI] = 69.5, 114.6), non-Hispanic Blacks (+67.6 mOsm/kg; 95% CI = 31.5, 103.6), and younger children (+28.5 mOsm/kg; 95% CI = 8.1, 48.9) compared with girls, Whites, and older children, respectively. Boys (OR = 1.76; 95% CI = 1.49, 2.07) and non-Hispanic Blacks (odds ratio [OR] = 1.34; 95% CI = 1.04, 1.74) were also at significantly higher risk for inadequate hydration. An 8-fluid-ounce daily increase in water intake was associated with a significantly lower risk of inadequate hydration (OR = 0.96; 95% CI = 0.93, 0.98). Conclusions. Future research should explore drivers of gender and racial/ethnic disparities and solutions for improving hydration status. Adequate hydration is essential for health. Water is crucial for the proper function of several physiological processes, including circulatory function, metabolism, temperature regulation, and waste removal. 1 Dehydration, a state in which total body water is inadequate for proper cell, organ, and system functioning, is associated with poor health. Although excessive dehydration is associated with serious health problems, such as impaired renal, immune, and gastrointestinal functioning, confusion, and delirium, even mild dehydration can worsen health and well-being. 2 Mild dehydration is associated with headache, irritability, poorer physical performance, and reduced cognitive functioning among both children and adults. 2–5 Children’s hydration status could have implications for both health and school performance. Two studies have shown that inadequate hydration, defined as urine osmolality of 800 milliosmoles per kilogram or higher, is associated with poorer performance on cognitive tests. 6,7 However, despite a substantial body of research examining children’s beverage intake, 8 little is known about children’s hydration status and whether it may be a population health concern. Kant et al. found that as of the period 2005 to 2006, US children and adolescents, on average, did not consume adequate water for their age group as defined by the Institute of Medicine, 9 but hydration status was not evaluated. A small study in 2 major US cities using urine osmolality as an indicator of hydration status found that over 60% of a convenience sample of children aged 9 to 11 years were inadequately hydrated and that most children did not consume plain water, putting them at higher risk of inadequate hydration. 10 However, we have identified no study describing children’s hydration status nationally. Additionally, although a review of international studies found significant differences in hydration status by age, gender, race/ethnicity, and culture, 11 there is limited evidence about the population distribution of urine osmolality and inadequate hydration among US children, particularly whether disparities in hydration status exist across population groups defined by race/ethnicity, household income, gender, or age. Although small, laboratory-based studies of adults suggest that higher beverage intake is associated with better hydration status (regardless of beverage type), 12,13 preliminary evidence has suggested that plain water may be associated with better hydration status in children. 10 Given that little is known about how consumption of different beverages may affect population hydration status in children, the potential solutions to reducing inadequate hydration are unclear. Measuring hydration status outside of severe dehydration has proven challenging because the level of fluid in the body is constantly fluctuating. Plasma osmolality, a measure of the amount of solutes in the blood stream, is often used to measure severe dehydration, but it has a very limited range and is tightly regulated by homeostasis, rendering it insensitive to smaller changes in hydration status. 12,14–16 Measures involving urine, such as urine volume or urine osmolality, are more sensitive to less dramatic changes in body water; however, the volume and timing of water intake can bias measurements. If individuals rapidly consume large amounts of water, their urine osmolality will be low and urine volume high as the body rapidly excretes the water, but their hydration status will be unaffected as the body will get rid of the excess water before it has a chance to rehydrate. Twenty-four-hour urine osmolality and 24-hour urine volume may be the most sensitive measures of 24-hour hydration status as time lags are better controlled. 11,14–16 Although a single measure of urine osmolality may not accurately reflect an individual’s typical hydration status because of fluctuation in urine osmolality, it may still be useful for estimating population averages. We would expect that observed fluctuations in the population would not be systematically biased above or below the mean. We examined the prevalence of elevated urine osmolality and its population distribution by age, race/ethnicity, gender, and family income in a nationally representative sample of participants aged 6 to 19 years from the National Health and Nutrition Examination Survey (NHANES), 2009 to 2012, 17 controlling for sample design and time of day the data were collected. We also examined whether consuming different types of beverages on the day before data collection, including water, milk, 100% juice, sugar-sweetened beverages (SSBs), and diet drinks, was associated with urine osmolality in this age group, hypothesizing that increased intake of water (compared with other beverages) would be associated with reduced urine osmolality.
