Voluntary dehydration among elementary school children residing in a hot arid environment

Seasonal changes in hydration in free-living Japanese children and adolescents

Changes in hydration status occur throughout the day affecting physiological and behavioural functions. However, little is known about the hydration status of free-living Japanese children and the seasonality of this response. We evaluated hydration status estimated by urine osmolality (Uosm) in 349 children (189 boys and 160 girls, 9.5 ± 2.6 years, range: 6-15 years) upon waking at home and during a single school day in spring (April) and summer (July). Further, we assessed the efficacy of employing self-assessment of urine colour (UC; based on an 8-point scale) by children to monitor their hydration status. Early morning Uosm was greater in the spring (903 ± 220 mOsm L-1; n = 326) as compared to summer (800 ± 244 mOsm L-1; n = 125) (P = 0.003, paired t test, n = 104). No differences, however, were observed in Uosm during the school day (P = 0.417, paired t test, n = 32). While 66% and 50% of children were considered underhydrated (Uosm ≥ 800 mOsm L-1) upon waking in the spring and summer periods, respectively, more children were underhydrated (∼12%) during the school day. Self-reported UC was similar between seasons as assessed in the morning and school day (P ≥ 0.101, paired t test), which differed from the pattern of responses observed with Uosm. We showed that a significant number of Japanese children are likely underhydrated especially in the spring period. Children do not detect seasonal changes in hydration from self-assessed UC, limiting its utility to manage hydration status in children.

A Study of Fluid Intake, Hydration Status, and Body Composition of Pregnant Women in Their Third Trimester, and Relationships with Their Infant's Birth Weight in China: A Prospective Cohort Study

BACKGROUND

Water intake and hydration status may potentially influence maternal and child health. However, there is little research regarding this topic.

OBJECTIVES

This study aimed to investigate pregnant women's total fluid intake (TFI) levels, hydration status, and body composition and further explore their relationship with infant birth weight.

METHODS

A 7-day, 24 h fluid intake recorded was applied to determine participants' TFI levels. Morning urine samples were collected and tested to evaluate their hydration status. Maternal body compositions in their third trimester and infant birth weights were measured.

RESULTS

A total of 380 participants completed the study. The TFI was insufficient for pregnant women during their third trimester (median = 1574 mL), with only 12.1% of participants meeting the recommended adequate fluid intake level for pregnant women living in China (1.7 L per day). With the increasing TFI values, the urine osmolality decreased, which showed statistical significance among the four groups (χ2 = 22.637, p < 0.05). The participants displayed a poor hydration status. Meanwhile, the percentage of participants who were in dehydrated status decreased (χ2 = 67.618, p < 0.05), while body water content and basal metabolic rate increased with the increase in TFI levels (χ2 = 20.784, p < 0.05; χ2 = 14.026, p < 0.05). There were positive linear relationships between plain water intake, the basal metabolic rate of pregnant women and their infant birth weight (SE = 0.153, p < 0.05; SE = 0.076, p < 0.05).

CONCLUSIONS

Water intake was insufficient, and poor hydration status was common among pregnant women in China. There may be potential relationships between plain water intake, basal metabolic rate, and infant birth weight.

The Amount of Fluid Intake among Pregnant Women in China Increases with Pregnancy Progression: A Prospective Cohort Study

Fluid intake and hydration status during pregnancy may have influences on maternal and infant health. However, few studies have recorded and analyzed total fluid intake (TFI) levels during the whole pregnancy. This study mainly aimed to investigate the TFI levels of pregnant women in three trimesters, and further to assess their hydration status. The relationships of TFI and hydration status were also analyzed. A convenience sampling method was used to recruit pregnant women from the Haikou Maternity and Child Health Hospital in China in this prospective cohort study. A 7-day 24 h fluid intake questionnaire was used for recording the fluid intake of the participants in their three trimesters. Fasting blood samples and first morning urine samples were also collected and tested. Hydration status was evaluated using urine osmolality. Finally, 142 pregnant women completed the study. The median TFIs in the first, second, and third trimesters were 1336, 1477, and 1584 mL, respectively. The TFI levels increased with pregnancy progression (χ2 = 134.155, p < 0.05). Out of 142 participants, 100.0%, 97.2%, and 85.2% of participants did not reach the recommendation amount for an adequate TFI among Chinese pregnant women in the three trimesters, respectively (χ2 = 29.840, p < 0.05). Plain water was the main source of fluid intake, accounting for 92.0%, 94.2%, and 93.4% of TFI, respectively. The median values of dairy product intake were 61, 57, and 59 mL in the three trimesters. The frequency of participants without an optimal hydration status in the three trimesters was 71.8%, 76.1%, and 83.1%, respectively (χ2 = 29.909, p < 0.05). The participants of each trimester were divided into four groups according to quartiles of TFI, including participants with a lower fluid intake (LFI1 and LFI2) and higher fluid intake (HFI1 and HFI2). As the TFI values increased from the LFI1 group to the HFI2 group, the urine osmolality decreased (all p < 0.05). Moderate-intensity negative correlations were found between urine osmolality, hydration status, and TFI (all p < 0.05). It is suggested that fluid intake strategies should be promoted and health education should be conducted to improve the hydration status of pregnant women.

A Study of the Fluid Intake, Hydration Status, and Health Effects among Pregnant Women in Their Second Trimester in China: A Cross-Sectional Study

The fluid intake and hydration status during pregnancy may influence the health outcomes of both the mother and the fetus. However, there are few studies related to this. The aim of the present study was to investigate fluid intake behaviors among pregnant women in their second trimester, to evaluate their hydration status and pregnancy complications, and to further explore the association of fluid intake and the amniotic fluid index (AFI). Participants’ total fluid intake (TFI) levels were determined using a 7-day 24 h fluid intake questionnaire. The levels of water intake from food were not recorded or measured. Morning urine samples were collected, and both urine osmolality levels and urine specific gravity (USG) were tested to evaluate their hydration status. Fasting blood samples were also collected and measured for osmolality and complete blood count (CBC). A total of 324 participants completed the study. They were divided into four groups based on quartiles of TFI, including participants with lower (LFI1 and LFI2) and higher (HFI1 and HFI2) fluid intake levels. The median TFI was 1485 mL, and the median values of the four groups with different TFI levels were 1348, 1449, 1530, and 1609 mL, respectively. Only 3.4% of the participants attained the recommended value following an adequate water intake (1.7 L) level for pregnant women in China. Plain water was the main TFI resource (78.8~100.00%), and differences in the plain water intake levels among the four groups were evident (χ2 = 222.027, p < 0.05). The urine osmolality decreased sequentially with increasing TFI values from the LFI1 to HFI2 group, and significant differences in the urine osmolality levels among the four groups were evident (p < 0.05). Meanwhile, the percentage of dehydrated participants decreased from 26.8% in the LFI1 group to 0.0% in the HFI2 group (χ2 = 131.241, p < 0.05). Participants with higher TFI values had higher AFI values (χ2 = 58.386, all p < 0.05), and moderate-intensity correlations were found between TFI and urine osmolality, hydration status, and AFI (all p < 0.05). A large proportion of the participants had insufficient TFIs during the second trimester of pregnancy, and a proportion of the participants were dehydrated. The preliminary analysis showed that the AFI was correlated with the TFI during the second trimester of pregnancy. A sufficient TFI is necessary for pregnant women to improve their hydration status and may have effects on their health. The results can provide appropriate scientific references for the development of beneficial recommendations concerning adequate water intake levels for pregnant women in China.

Behaviors of Water Intake, Hydration Status, and Related Hydration Biomarkers among Physically Active Male Young Adults in Beijing, China: A Cross-Sectional Study

Studies on the water intake of athletes in daily life are insufficient. The objective was to determine the water intake and hydration status among physically active male young adults. In this cross-sectional studies study, 111 physically active male young adults were recruited. The amount of daily total drinking fluid intake (TDF) among participants was recorded and evaluated in real time over 7 days using the "7-day 24-hour fluid intake questionnaire" (liq. In 7). The daily water intake from food (WFF) was calculated using the weighing, duplicate portion, and direct-drying method over 3 days. All urine samples over 3 days were collected, and urine biomarkers were determined. According to 24 h urine osmolality, the participants were divided into three groups with euhydration status, middle hydration, and hypo hydration statuses. Finally, 109 participants completed the study. The median daily total water intake (TWI), TDF, and WFF were 2701, ik1789, and 955 mL, respectively. Among participants, 17 participants (16%) were in euhydration status, 47 participants (43%) were in hypohydration, and 45 participants (41%) were in middle hydration. There were statistical significances in the 24 h urine volume, osmolality, urine specific gravity, and concentrations of K, Na, and Cl in different hydration statuses (χ 2  = 28.212, P < 0.01; χ 2  = 91.341, P < 0.01; χ 2  = 47.721, P < 0.01; χ 2  = 41.548, P < 0.01; χ 2  = 46.863, P < 0.01; and χ 2  = 40.839, P < 0.01). Moderate-intensity correlations were found between the TDF and 24 h urine volume, 24 h urine osmolality, 24 h urine Na concentration, morning urine osmolality, and morning urine Na concentration (r = 0.408, P < 0.01; r = -0.378, P < 0.01; r = -0.325, P < 0.01; r = -0.344, P < 0.01; and r = -0.329, P < 0.01). There were also moderate-intensity correlations between the TDF and 24 h urine osmolality, morning urine osmolality, and morning urine Na concentration (r = -0.365, P < 0.01; r = -0.371, P < 0.01; and r = -0.322, P = 0.01). Increased and higher moderate-intensity correlations were found between plain water and 24 h urine volume, 24 h urine osmolality, 24 h urine K and Na concentration, morning urine osmolality, and morning urine Na concentration (r = 0.374, P < 0.01; r = -0.520, P < 0.01; r = -0.312,P < 0.01; r = -0.355, P < 0.01; r = -0.446, P < 0.01; and r = -0.378, P < 0.01). Insufficient water intake and hypohydration were common among physically active male young adults. The amount and type of water intake were correlated with hydration status and urine biomarkers. The results could provide scientific and accurate references for the development of recommendations on water intake for athletes.

Current Hydration Habits: The Disregarded Factor for the Development of Renal and Cardiometabolic Diseases

Improper hydration habits are commonly disregarded as a risk factor for the development of chronic diseases. Consuming an intake of water below recommendations (underhydration) in addition to the substitution of sugar-sweetened beverages (SSB) for water are habits deeply ingrained in several countries. This behavior is due to voluntary and involuntary dehydration; and because young children are exposed to SSB, the preference for a sweet taste is profoundly implanted in the brain. Underhydration and SSB intake lead to mild hyperosmolarity, which stimulates biologic processes, such as the stimulation of vasopressin and the polyol-fructose pathway, which restore osmolarity to normal but at the expense of the continued activation of these biological systems. Unfortunately, chronic activation of the vasopressin and polyol-fructose pathways has been shown to mediate many diseases, such as obesity, diabetes, metabolic syndrome, chronic kidney disease, and cardiovascular disease. It is therefore urgent that we encourage educational and promotional campaigns that promote the evaluation of personal hydration status, a greater intake of potable water, and a reduction or complete halting of the drinking of SSB.

Is there a functional relationship between hydration and memory in children and adolescents? A meta-analysis

Objective: Hydration can favor cognitive functions during childhood and adolescence, helping with daily and school activities. This study aimed to identify possible interactions between hydration and memory in children and adolescents. Methods: This is a systematic review with meta-analysis. The bibliographic search was conducted in the MEDLINE/PubMed, SciELO, LILACS, Web of Science, Embase, and Cochrane Library databases, through a combination of the descriptors: “hydration” AND “memory”; “hydration” AND “memory” AND “child”; “hydration” AND “memory” AND “children”; “organism hydration status” AND “memory”; “organism hydration status” AND “memory” AND “child”. Results: The search resulted in 816 articles, of which ten were selected for qualitative synthesis and two for the meta-analysis. The results indicated that hydration could not enhance working, visual and visuomotor memories, or visual attention (Line Tracing Task, MD 0.67, 95% CI -0.87 to 2.22; Indirect Image Difference, MD 0.32, 95% CI -0.75 to 1.40; Letter Cancellation, MD 1.68, 95% CI -0.81 to 4.17). Conclusion: From the obtained results, hydration per se does not reinforce working, visual and visuomotor memories, or visual attention. However, there are still gaps regarding other types of memory and cognitive, motor, nutritional and environmental integration.

Detection of voluntary dehydration in paediatric populations using non-invasive point-of-care saliva and urine testing

AIM

Voluntary dehydration, or lack of fluid intake despite water availability, is common in otherwise healthy children, and can lead to adverse effects. Most dehydration biomarkers are impractical for routine assessment in paediatric populations. This study aimed to assess two non-invasive hydration assessment tools, urine specific gravity (U_SG ) and a novel point-of-care (POC) salivary osmolarity (SOSM) sensor, in healthy children.

METHODS

Volunteers were tested by colorimetric U_SG and a handheld SOSM system. Observed values were compared against previous studies to determine hydration status, as was the concordance between parameters.

RESULTS

At the common U_SG threshold of 1.020, 42.4% of the 139 healthy children were dehydrated. The same prevalence was found using the 70-mOSM cut-off value. Comparative analysis of SOSM at varying U_SG thresholds demonstrated significantly higher SOSM in dehydrated children with a U_SG  ≥ 1.030 (P = 0.002).

CONCLUSION

At the U_SG threshold of 1.020 and SOSM threshold of 70 mOSM, 42.4% of healthy children were found to be voluntarily dehydrated. Significantly higher SOSM was observed in dehydrated children (U_SG  ≥ 1.030). As the first study on the utility of POC SOSM measurements for detecting dehydration, these results provide a foundation for future POC characterisation of SOSM in other populations and clinical contexts.

Dehydration in older people: A systematic review of the effects of dehydration on health outcomes, healthcare costs and cognitive performance

OBJECTIVE

To systematically examine the effect of dehydration on health outcomes, identify associated financial costs and consider impacts on cognitive performance in older adults.

DESIGN

A systematic review of English-language articles via OVID using MEDLINE, PsychINFO, EMBASE, and others, to March 2018. Included studies examined the relationship between hydration status and health, care costs or cognitive outcome.

SETTING

Cross sectional and cohort data from studies reporting on dehydration in older adults.

PARTICIPANTS

Adults aged 60 years and older.

MEASUREMENTS

Independent quality ratings were assessed for all extracted articles.

RESULTS

Of 1684 articles screened, 18 papers (N = 33,707) met inclusion criteria. Participants were recruited from hospital settings, medical long-term care centres and the community dwelling population. Data were synthesised using a narrative summary. Mortality rates were higher in dehydrated patients. Furthermore, health outcomes, including frailty, bradyarrhythmia, transient ischemic attacks, oral health and surgery recovery are linked to and worsened by dehydration. Length of hospital stay, either as a principal or secondary diagnosis, is greater in those with dehydration, compared to those who are euhydrated. Finally, neurocognitive functioning may be impacted by dehydration. There are issues with study design, inconsistency in hydration status measurement and different measures used for outcome assessment.

CONCLUSION

Dehydration in older people is associated with increased mortality, poorer course of illness and increased costs for health services. In addition, there is some, but sparse evidence that dehydration in older people is linked to poorer cognitive performance. Intervention studies should test strategies for reducing dehydration in older adults.

Protocol for a Trial Assessing the Impacts of School-Based WaSH Interventions on Children's Health Literacy, Handwashing, and Nutrition Status in Low- and Middle-Income Countries

Diarrhea, soil-transmitted helminth infection and malnutrition are leading causes of child mortality in low- and middle-income countries (LMICs). To reduce the prevalence of these diseases, effective interventions for adequate water, sanitation, and hygiene (WaSH) should be implemented. This paper describes the design of a cluster-randomized controlled trial that will compare the efficacy of four school-based WaSH interventions for improving children’s health literacy, handwashing, and nutrition. Interventions consisted of (1) WaSH policy reinforcement; (2) low-, medium-, or high-volume health education; (3) hygiene supplies; and (4) WaSH facilities (e.g., toilets, urinals, handwashing basins) improvements. We randomly allocated school clusters from the intervention arm to one of four groups to compare with schools from the control arm. Primary outcomes were: children’s health literacy, physical growth, nutrition status, and handwashing prevalence. Secondary outcomes were: children’s self-reported health status and history of extreme hunger, satisfaction with WaSH facilities, and school restrooms’ WaSH adequacy. We will measure differences in pre- and post-intervention outcomes and compare these differences between control and intervention arms. This research protocol can be a blueprint for future school-based WaSH intervention studies to be conducted in LMICs. Study protocols were approved by the ethics committees of the University of Bonn, Germany, and the University of the Philippines Manila. This trial was retroactively registered, ID number: DRKS00021623.

Effects of the Amount and Frequency of Fluid Intake on Cognitive Performance and Mood among Young Adults in Baoding, Hebei, China: A Randomized Controlled Trial

Water is a critical nutrient that is important for the maintenance of the physiological function of the human body. This article aimed to investigate the effects of the amount and frequency of fluid intake on cognitive performance and mood. A double-blinded randomized controlled trial was designed and implemented on college students aged 18–23 years in Baoding, China. Participants were randomly assigned into one of three groups: the recommended behavior group (RB group) who drank 200 mL of water every 2 h, the half amount group (HA group) who drank 100 mL of water every 2 h, and the high frequency group (HF group) who drank 110 mL of water every 1 h. The intervention lasted 2 days. Urine osmolality, cognitive performance, and mood of participants in each group were compared using the one-way analysis of variance (ANOVA). A total of 92 participants (46 females, 46 males) completed this study with a completion rate of 95.8%. The urine osmolality of the HA group was higher than that of the RB group and the HF group at two time points (p < 0.05). At time point 1, the scores in the portrait memory test and vigor were statistically different (F = 20.45, p < 0.001; F = 5.46, p = 0.006). It was found that the scores for the portrait memory test in the RB group were lower than those in the HA group and the HF group (p = 0.007; p < 0.001), while the scores of the HF group were higher than those of the HA group (p < 0.001). The scores for vigor in the RB group were significantly higher than those of the HA group (p = 0.006), and they were also significantly higher than those of the HF group (p = 0.004). At time point 2, only the scores for vigor were statistically different (F = 3.80, p = 0.026). It was found that the scores for vigor in the RB group were higher than those in the HA group and HF group (p = 0.018; p = 0.019). Both the amount and frequency of fluid intake may affect urine osmolality and vigor, but these factors have limited impacts on cognitive performance. Rational fluid intake behavior may be beneficial to improve the hydration status and mood of young adults. More research is needed, especially experimental research, to allow causal conclusions to be drawn.

Restricted Water Intake and Hydration with Fructose-Containing Beverages during Infancy Predispose to Aggravate an Acute Renal Ischemic Insult in Adolescent Rats

We aimed to investigate the effects of chronic fluid restriction and hydration with a sweetened beverage (SB) in rats from weaning until adolescence, in a posterior acute kidney injury (AKI) event induced by ischemia-reperfusion (I/R). We followed 5 groups of weaning rats: control group (C); two groups with 22 h/day fluid restriction, a group hydrated for two hours with water (-W) and a group hydrated with SB; one group receiving SB ad libitum all day (+SB); and one group in which water consumption was increased using a gel diet. The rats that reached adolescence were submitted to I/R. Fluid restriction and/or SB hydration induced mild renal alterations that were significantly accentuated in the -SB group and resulted in worse outcomes after I/R-induced AKI that resulted in a catastrophic fall in creatinine clearance and diffuse acute tubular necrosis. In summary, low tap water intakes, as well as SB intake in infancy, prompt kidney worse outcomes in a later event of AKI during adolescence and both insults magnify kidney damage. Studies on hydration habits in children are recommended to disclose the potentially harmful effects that those behavioral patterns might carry to future renal health.

Afternoon urine osmolality is equivalent to 24 h for hydration assessment in healthy children

BACKGROUND/OBJECTIVES

While daily hydration is best assessed in 24-h urine sample, spot sample is often used by health care professionals and researchers due to its practicality. However, urine output is subject to circadian variation, with urine being more concentrated in the morning. It has been demonstrated that afternoon spot urine samples are most likely to provide equivalent urine concentration to 24-h urine samples in adults. The aim of the present study was to examine whether urine osmolality (UOsm) assessed from a spot urine sample in specific time-windows was equivalent to 24-h UOsm in free-living healthy children.

SUBJECTS/METHODS

Among 541 healthy children (age: 3-13 years, female: 45%, 77% non-Hispanic white, BMI:17.7 ± 4.0 kg m^-2), UOsm at specific time-windows [morning (0600-1159), early afternoon (1200-1559), late afternoon (1600-1959), evening (2000-2359), overnight (2400-0559), and first morning] was compared with UOsm from the corresponding pooled 24-h urine sample using an equivalence test.

RESULTS

Late afternoon (1600-1959) spot urine sample UOsm value was equivalent to the 24-h UOsm value in children (P < 0.05; mean difference: 62 mmol kg^-1; 95% CI: 45-78 mmol kg^-1). The overall diagnostic ability of urine osmolality assessed at late afternoon (1600-1959) to diagnose elevated urine osmolality on the 24-h sample was good for both cutoffs of 800 mmol kg^-1 [area under the curve (AUC): 87.4%; sensitivity: 72.6%; specificity: 90.5%; threshold: 814 mmol kg^-1] and 500 mmol kg^-1 (AUC: 83.5%; sensitivity: 75.0%; specificity: 80.0%; threshold: 633 mmol kg^-1).

CONCLUSION

These data suggest that in free-living healthy children, 24-h urine concentration may be approximated from a late afternoon spot urine sample. This data will have practical implication for health care professionals and researchers.

Water and Beverage Consumption among a Nationally Representative Sample of Children and Adolescents in the United Arab Emirates

There are limited studies examining water consumption among individuals in hot climates. We assessed the daily total water intake from plain water, other beverages, and food in a nationally representative sample of children and adolescents aged 6-18 years in the United Arab Emirates. Total water intake was compared against the recommendations of the Institute of Medicine and the European Food Safety Authority. Sociodemographic information, 24 h dietary recall, physical activity levels, and anthropometric data were collected from 527 participants. The mean ± SE of total water intake was 1778.4 ± 33.8 mL/day. Plain drinking water was the largest contributor to total water intake (51.6%), followed by food (27.3%). Sugar-sweetened beverages constituted 13.9% of water intake. The proportion of participants who met the Institute of Medicine recommendations ranged from 15% (males aged 14-18) to 25% (children aged 6-8). The proportion of participants who met the European Food Safety Authority recommendations ranged from 31% (females aged 14-18) to 36% (males aged 14-18). The water-to-energy ratio was 1.0-1.15 L/1000 kcal, meeting recommendations. The majority of participants failed to meet water intake recommendations, highlighting the need for targeted interventions to promote increased water consumption among children and adolescents.

Hydration status, total water intake and subjective feelings of adolescents living in a hot environment, during a typical school day

AIM

Individuals living in a hot environment appear to face increased risk of dehydration. Currently there is not extensive literature on the adolescent population in relation to hydration. The aim of the present study was to assess hydration status and total water intake (TWI) at school, of adolescents living in a hot environment, and to investigate the association of hydration and TWI with various subjective feelings.

METHODS

The hydration status of 141 adolescents (boys n = 102), age 15-17 years, was assessed via urine specific gravity (USG), at the beginning (07:30 am) and at the end (1:30 pm) of one school day. TWI from fluids and solid food was assessed via detailed food and fluid records. Subjective feelings (i.e. thirst, alertness, ability to concentrate) were recorded by specific scales.

RESULTS

Ninety percent of the students arrived dehydrated at school (USG >1.020). Thirteen students were hydrated (USG <1.020), 67 students were slightly dehydrated (USG 1.021-1.029), and 50 students were seriously dehydrated (USG >1.030). There was no difference in TWI between the three groups (765 ± 451 mL). TWI correlated with alertness (p = 0.005) and the ability to concentrate (p = 0.015), and inversely correlated with fatigue (p = 0.015). Seriously dehydrated students felt less alert in the morning (p < 0.035) whereas the feeling of thirst was similar between all groups.

CONCLUSIONS

The prevalence of the dehydration of the adolescents during school time appeared to be extremely high, and thirst was not driving those adolescents to drink enough. Apart from health concerns, school performance could be affected by dehydration and inadequate water intake.

Analysis of 2009⁻2012 Nutrition Health and Examination Survey (NHANES) Data to Estimate the Median Water Intake Associated with Meeting Hydration Criteria for Individuals Aged 12⁻80 in the US Population

In 2005, US water intake recommendations were based on analyses of Nutrition Health and Examination Surveys (NHANES) III data that examined if hydration classification varied by water intake and estimated the median water intake associated with hydration in persons aged 19–30. Given the upcoming 2020–2025 Dietary Guidelines review, this analysis addressed the same two aims with 2009–2012 NHANES data. Methods were updated by defining hydration criteria in terms of multiple measures (serum sodium 135–144 mmol/L and urine osmolality < 500 mmol/kg), expressing water intake as ml/kg, distinguishing plain water intake (PWI) from total water intake (TWI), using weighted age- and sex-specific multivariable models to control for determinants of water intake requirements, and selecting two study samples (the non-acutely ill US population and a sub-group without selected chronic disease risk factors). In the US population and sub-group, the relative risk (RR) of meeting the hydration criteria was significantly greater for individuals with TWI ≥ 45 mL/kg or PWI ≥ 20 mL/kg (for the US population 19–50 years of age: adjusted RR = 1.36, 95% CI: 1.10–1.68 for males; adjusted RR = 1.70, 95% CI: 1.49–1.95 for females. For the sub-group 51–70 years of age: adjusted RR = 2.20, 95% CI: 1.15–4.18 for males; adjusted RR = 2.00, 95% CI: 1.18–3.40 for females). The median (SE) TWI and PWI associated with meeting the hydration criteria for males and females 19–50 years of age were 42 (2) mL/kg and 14 (1) mL/kg and 43 (2) mL/kg and 16 (1) mL/kg, respectively. The significant association between water intake and hydration classification differs from the null association underlying the 2005 water intake recommendations and may lead to different reasoning and inferences for the 2020–2025 Dietary Guidelines.

The impact of water consumption on hydration and cognition among schoolchildren: Methods and results from a crossover trial in rural Mali

Adequate provision of safe water, basic sanitation, and hygiene (WASH) facilities and behavior change can reduce pupil absence and infectious disease. Increased drinking water quantity may also improve educational outcomes through the effect of hydration on attention, concentration, and short-term memory. A pilot study was conducted to adapt field measures of short-term cognitive performance and hydration, to evaluate levels of hydration, and to investigate the impact of providing supplementary drinking water on the cognitive performance of pupils attending water-scarce schools in rural Mali. Using a cross-over trial design, data were collected under normal school conditions (control condition) on one visit day; on the other, participants were given a bottle of water that was refilled throughout the day (water condition). Morning and afternoon hydration was assessed using specific gravity and urine color. Cognitive performance was evaluated using six paper-based tests. Three percent of pupils were dehydrated on the morning of each visit. The prevalence of dehydration increased in the afternoon, but was lower under the water condition. Although there was a trend indicating drinking water may improve cognitive test performance, as has been shown in studies in other settings, results were not statistically significant and were masked by a "practice effect."

Prevalence of voluntary dehydration according to urine osmolarity in elementary school students in the metropolitan region of São Paulo, Brazil

OBJECTIVES

To evaluate the prevalence of voluntary dehydration based on urine osmolarity in elementary school students from two public educational institutions in the metropolitan region of São Paulo and evaluate whether there is a relationship between voluntary dehydration and nutritional status or socioeconomic status.

METHODS

Analytical cross-sectional study with students from two public schools in the city of Osasco. The determination of urine osmolarity was performed using the freezing method of the Advanced® Osmometer Model 3W2. Urine osmolarity greater than 800 mOsm/kg H2O was considered voluntary dehydration. During data collection, the weights and heights of the students, environmental temperatures and air humidity levels were obtained.

RESULTS

A total of 475 students aged six to 12 years were evaluated, of whom 188 were male. Voluntary dehydration occurred in 63.2% of the students and was more frequent in males than in females. The prevalence of voluntary dehydration was more frequent in males aged six to nine years than in females. However, no statistically significant difference was observed between males and females aged 10 to 12 years. No association was found between voluntary dehydration and nutritional status or socioeconomic status.

CONCLUSION

The prevalence of voluntary dehydration was high in elementary school students and was more frequent in males. No association was found between voluntary dehydration and nutritional or socioeconomic status.

Physical activity and sedentary behavior impacts on dietary water intake and hydration status in Spanish schoolchildren: A cross-sectional study

BACKGROUND

The importance of maintaining an adequate hydration status and the complexity of the water balance make it necessary to study the lifestyle factors that can influence or modify these variables. The aim of this study was to evaluate the hydration status and dietary water intake for a sample of Spanish schoolchildren from 7 to 12 years old and their associations with physical activity (PA) and sedentary behaviors.

METHODS

A total of 242 schoolchildren was studied (49.17% females). A 24-hour urine sample was collected from each child, and the urine volume and osmolality were measured to estimate the hydration status (adequate hydration ≤800 mOsm/kg). In addition, a 3-day dietary record was completed to evaluate their water intake according to EFSA parameters. Dietary information was processed with DIAL software, and a statistical analysis was performed using SPSS. Student's t-test was used to study the normal variables, and the Mann-Whitney U test was used for those that were not normal. In the case of the categorical variables, the Z and Chi-Square proportions tests were used. The Bonferroni test was used to adjust the values in multiple comparisons. To evaluate the influence of these lifestyles on the urine osmolality, a 2-way ANOVA and an odds ratio were used.

RESULTS

A total of 48.3% of the sample presented an adequate hydration status, and the percentage was significantly higher in females (p = 0.003). Only 20.9% showed an adequate intake of dietary water. The lifestyle influence reveals that more inactive and non-sedentary schoolchildren were adequately hydrated (p = 0.008). PA (practice ≥1 h/day) was associated with a higher risk of having an inadequate hydration status, even when accounting for sex and other lifestyle factors (OR = 1.753(1.006-3.054), p = 0.048).

CONCLUSIONS

Approximately half of the participants presented an inadequate hydration status (which was higher in males than in females). PA (practice ≥1 h/day) was associated with a higher risk of inadequate hydration. This fact highlighted the importance of raising awareness about hydration in children, especially in ones who are more active.

Water intake and hydration state in children

PURPOSE

Although low water intake has been associated with adverse health outcomes, available literature indicated that the majority of children do not meet the water intake guidelines and they are underhydrated based on elevated hydration biomarkers. This review examined the water intake habits and hydration status in children from 32 observational studies (n = 36813).

METHODS

PubMed, Web of Science, and CINAHL were used to identify relevant articles. Total water/fluid intake from 25 countries was compared with water intake recommendations and underhydration (urine osmolality greater than 800 mmol kg^-1) was assessed. Risk of bias was assessed using customized categories following the review guideline for observational studies.

RESULTS

From 32 studies, only 11 studies reported both water intake and hydration status. 12 out of 24 studies reported mean/median water/fluid intake below the guidelines, while 4 out of 13 studies that assessed hydration status indicated underhydration based on urine osmolality (greater than 800 mmol kg^-1). Among the 19 countries that reported comparison of water/fluid intake with guidelines, 60 ± 24% of children (range 10-98%) failed to meet them.

CONCLUSION

These findings suggest that children are not consuming enough water to be adequately hydrated.

Validation of a survey to examine drinking-water access, practices and policies in schools

OBJECTIVE

Ensuring ready access to free drinking-water in schools is an important strategy for prevention of obesity and dental caries, and for improving student learning. Yet to date, there are no validated instruments to examine water access in schools. The present study aimed to develop and validate a survey of school administrators to examine school access to beverages, including water and sports drinks, and school and district-level water-related policies and practices.

DESIGN

Survey validity was measured by comparing results of telephone surveys of school administrators with on-site observations of beverage access and reviews of school policy documents for any references to beverages. The semi-structured telephone survey included items about free drinking-water access (sixty-four items), commonly available competitive beverages (twenty-nine items) and water-related policies and practices (twenty-eight items). Agreement between administrator surveys and observation/document review was calculated using kappa statistics for categorical variables, and Pearson correlation coefficients and t tests for continuous variables.

SETTING

Public schools in the San Francisco Bay Area, California, USA.

SUBJECTS

School administrators (n 24).

RESULTS

Eighty-one per cent of questions related to school beverage access yielded κ values indicating substantial or almost perfect agreement (κ>0·60). However, only one of twenty-eight questions related to drinking-water practices and policies yielded a κ value representing substantial or almost perfect agreement.

CONCLUSIONS

This school administrator survey appears reasonably valid for questions related to beverage access, but less valid for questions on water-related practices and policies. This tool provides policy makers, researchers and advocates with a low-cost, efficient method to gather national data on school-level beverage access.

Water, sanitation, and hygiene in schools: Status and implications of low coverage in Ethiopia, Kenya, Mozambique, Rwanda, Uganda, and Zambia

Adequate access to water, sanitation, and hygiene (WaSH) in schools impacts health, educational outcomes, and gender disparities. Little multi-country research has been published on WaSH in rural schools in Sub-Saharan Africa. In this multi-national cross-sectional WaSH study, we document WaSH access, continuity, quality, quantity, and reliability in 2270 schools that were randomly sampled in rural regions of six Sub-Saharan African countries: Ethiopia, Kenya, Mozambique, Rwanda, Uganda, and Zambia. Data collection included: school WaSH surveys containing internationally established WaSH indicators, direct observation, and field- and laboratory-based microbiological water quality testing. We found 1% of rural schools in Ethiopia and Mozambique to 23% of rural schools in Rwanda had improved water sources on premises, improved sanitation, and water and soap for handwashing. Fewer than 23% of rural schools in the six countries studied met the World Health Organization's recommended student-to-latrine ratios for boys and for girls. Fewer than 20% were observed to have at least four of five recommended menstrual hygiene services (separate-sex latrines with doors and locks, water for use, waste bin). The low access to safe and adequate WaSH services in rural schools suggest opportunities for WaSH interventions that could have substantive impact on health, education, and gender disparities.

Urine color as an indicator of urine concentration in pregnant and lactating women

AIM

Urine concentration measured via osmolality (U OSM) and specific gravity (U SG) reflects the adequacy of daily fluid intake, which has important relationships to health in pregnant (PREG) and lactating (LACT) women. Urine color (U COL) may be a practical, surrogate marker for whole-body hydration status.

PURPOSE

To determine whether U COL was a valid measure of urine concentration in PREG and LACT, and pair-matched non-pregnant, non-lactating control women (CON).

METHODS

Eighteen PREG/LACT (age 31 ± 1 years, pre-pregnancy BMI 24.3 ± 5.9 kg m-2) and eighteen CON (age 29 ± 4 years, BMI 24.1 ± 3.7 kg m-2) collected 24-h and single-urine samples on specified daily voids at five time points (15 ± 2, 26 ± 1, and 37 ± 1 weeks gestation, 3 ± 1 and 9 ± 1 weeks postpartum during lactation; CON visits were separated by similar time intervals) for measurement of 24-h U OSM, U SG, and U COL and single-sample U OSM and U COL.

RESULTS

Twenty-four-hour U COL was significantly correlated with 24-h U OSM (r = 0.6085-0.8390, P < 0.0001) and 24-h U SG (r = 0.6213-0.8985, P < 0.0001) in all groups. A 24-h U COL ≥ 4 (AUC = 0.6848-0.9513, P < 0.05) and single-sample U COL ≥ 4 (AUC = 0.9094-0.9216, P < 0.0001) indicated 24-h U OSM ≥ 500 mOsm kg-1 (representing inadequate fluid intake) in PREG, LACT, and CON.

CONCLUSIONS

Urine color was a valid marker of urine concentration in all groups. Thus, PREG, LACT, and CON can utilize U COL to monitor their daily fluid balance. Women who present with a U COL ≥ 4 likely have a U OSM ≥ 500 mOsm kg-1 and should increase fluid consumption to improve overall hydration status.

What is Known About Health and Morbidity in the Pediatric Population of Muslim Bedouins in Southern Israel: A Descriptive Review of the Literature from the Past Two Decades

The Bedouins comprise one of the ethnic groups in Israeli society. They are Muslims, most of who live in the Negev desert region of southern Israel and live by their unique traditions and customs. At the present they are going through a period of "society in transition", a unique condition that has ramifications for health and morbidity. In recent years the number of publications on the health of Bedouins in the Negev has increased. Recognition of unique socio-economic features, characteristics of health and diseases can help the medical team treat various health problems in this population as well as other populations with similar characteristics. In the present paper we survey and discuss publications on the health of Bedouin children over the past 20 years.

Water intake and urinary hydration biomarkers in children

BACKGROUND/OBJECTIVES

The aims of the study were as follows: (1) examine fluid intake and urinary hydration markers of children in Greece, (2) determine the calculated relative risk of hypohydration in children who did not meet the recommendations for daily water intake provided by the Institute of Medicine and the European Food Safety Authority compared with those who did and (3) analyze the efficacy of the recommendations as a method to achieve euhydration in children.

SUBJECTS/METHODS

One hundred and fifty Greek boys and girls (age 9-13) recorded their fluid intake for 2 consecutive days. A 24-h urine collection was obtained during the second day. Fluid intake records were analyzed for total water intake from fluids (TWI-F), and urine samples were analyzed for osmolality, color, specific gravity and volume. Urine osmolality ⩾800 mmol/kg H₂O was defined as hypohydration.

RESULTS

Water intake from fluids was 1729 (1555-1905) and 1550 (1406-1686) ml/d for boys and girls, respectively. Prevalence of hypohydration was 33% (44% of boys, 23% of girls). Children who failed to meet TWI-F recommendations demonstrated a risk of hypohydration that was 1.99-2.12 times higher than those who met recommendations (P⩽0.01). Boys between 9 and 13 years displayed urine osmolality of 777 (725-830) mmol/kg, and urine specific gravity of 1.021 (1.019-1.022), which was higher than those in girls between 9-13 years (P⩽0.015), and >27% were classified as hypohydrated despite meeting water intake recommendations.

CONCLUSIONS

Failure to meet TWI-F guidelines increased calculated relative risk of hypohydration in children. Boys between 9 and 13 years are at greater hazard regardless of meeting guidelines and may require greater water intake to avoid elevated urine concentration and ensure adequate hydration.

Effects of Water Provision and Hydration on Cognitive Function among Primary-School Pupils in Zambia: A Randomized Trial

There is a well-established link between hydration and improved cognitive performance among adults, with evidence of similar findings among children. No trials have investigated the impact of water provision on cognitive performance among schoolchildren in hot and arid low-resource settings. We conducted a randomized-controlled trial in five schools with limited water access in Chipata district in Eastern province, Zambia, to assess the efficacy of water provision on cognition. Pupils in grades 3–6 were randomly assigned to either receive a bottle of drinking water that they could refill throughout the day (water group, n = 149) or only have access to drinking water that was normally available at the school (control group, n = 143). Hydration was assessed in the morning before provision of water and in the afternoon through urine specific gravity (U_sg) measured with a portable refractometer. In the afternoon we administered six cognitive tests to assess short-term memory, concentration, visual attention, and visual motor skills. Morning prevalence of dehydration, defined as U_sg≥1.020, was 42%. Afternoon dehydration increased to 67% among the control arm and dropped to 10% among the intervention arm. We did not find that provision of water or hydration impacted cognitive test scores, although there were suggestive relationships between both water provision and hydration and increased scores on tests measuring visual attention. We identified key improvements to the study design that are warranted to further investigate this relationship.

Trial Registration: ClinicalTrials.gov NCT01924546

Belgian primary school children's hydration status at school and its personal determinants

PURPOSE

Dehydration has been related to several health aspects, and children are especially vulnerable. Since children spend a large time at school, we aim to examine children's hydration status at school-start and its change during the school-day by objective measures. To identify subpopulations at risk, determinants of hydration were tested.

METHODS

In 371 Belgian 7-13-year-old children, hydration was measured by (1) urinary osmolality at school-start and by a pooled school-day sample; (2) body water% by impedance; (3) parental reported beverage consumption; (4) urination frequency. Linear regression analyses were used to test putative predictors of hydration status: age, sex, parental education, region (Dutch-speaking versus French-speaking part of Belgium), diet quality and adiposity.

RESULTS

A mean osmolality of 888 mosmol/kg was found in the school-start sample and 767 mosmol/kg in the school-day sample. This resulted in, respectively, 76 and 54 % of the children being dehydrated (>800 mosmol/kg). In 45 % of the children, the hydration level decreased over the school-day. Also the body water% as derived from bio-impedance (57 % ±4), the reported average daily beverage intake (911 ml) and the lower urination frequency during weekdays versus weekend days confirmed the low hydration status in our school population. Boys, Walloon children and those with higher adiposity were at increased risk of low hydration level. Diet quality was not the predictor of hydration status.

CONCLUSIONS

Hydration status at school appeared problematic in this population. This emphasizes the need for more resources and attention by school management and governmental organizations. Herein, especially Walloon schools and boys should be reached.

Fluid consumption, total water intake and first morning urine osmolality in Spanish adolescents from Zaragoza: data from the HELENA study

BACKGROUND/OBJECTIVES

The objective of the study is to describe the hydration status and to assess the main food- and/or fluid intake-associated factors in healthy adolescents.

SUBJECTS/METHODS

A total of 194 adolescents from the city of Zaragoza aged 12.5-17.5 years (99 males) participating in the 'Healthy Lifestyle in Europe by Nutrition in Adolescence' (HELENA) cross-sectional study were included. First morning urine was collected, and osmolality was determined by freezing point depression osmometer. A self-reported computer-based 24-h dietary recall was applied the same day of the urine collection. Analysis of variance, Kruskal-Wallis procedure or Pearson's χ(2) analyses was used to examine the group associations.

RESULTS

Seventy-one percent of adolescents did not meet the European Food Safety Agency (EFSA) recommendations for average total water intake (TWI), and 68% had high first morning urine osmolality values. TWI and the proportion of those meeting EFSA reference values significantly (P<0.05) decreased with increased osmolality. Males who met the EFSA recommendations consumed significantly (P<0.05) more plain water (1035.13 vs 582.68 ml) and dairy drinks (368.13 vs 226.68 ml) than those who did not. In females, the consumption of water (1359.41 vs 620.44 ml) and sugar-sweetened beverages (214.61 vs 127.42 ml) was significantly higher in those meeting the EFSA recommendations than in those who did not. First morning urine osmolality was associated with vegetables (unstandardized β: -0.6; 95% confidence interval (CI): -1.02 and -0.18) and fruits intake (β: -0.41; 95% CI: -0.63 and -0.19) in males and with dairy drinks (β: -0.39; 95% CI: -0.76 and -0.02) and fruits (β: -0.41; 95% CI: -0.73 and -0.10) in females.

CONCLUSIONS

There was a high prevalence of inadequate TWI and high urine osmolality among these Spanish adolescents. Lower urine osmolality was associated with higher consumption of vegetables in males, dairy drinks in females and fruits in both males and females.

Hydration Deficit in 9- to 11-Year-Old Egyptian Children

Background. Children who drink too little to meet their daily water requirements are likely to become dehydrated, and even mild dehydration can negatively affect health. This is even more important in Middle-Eastern countries where high temperatures increase the risk of dehydration. We assessed morning hydration status in a sample of 519 Egyptian schoolchildren (9-11 years old). Methods. Children completed a questionnaire on breakfast intakes and collected a urine sample after breakfast. Breakfast food and fluid nutritional composition was analyzed and urine osmolality was measured using osmometry. Results. The mean urine osmolality of children was 814 mOsmol/kg: >800 mOsmol/kg (57%) and >1000 mOsmol/kg (24.7%). Furthermore, the results showed that a total water intake of less than 400 mL was associated with a significant higher risk of dehydration. Surprisingly, 63% of the children skipped breakfast. Conclusions. The results showed that a majority of Egyptian schoolchildren arrive at school with a hydration deficit. These results highlight the fact that there is a need to educate schoolchildren about the importance of having a breakfast and adequate hydration.

An empirical method to determine inadequacy of dietary water

OBJECTIVES

The physiological regulation of total body water and fluid concentrations is complex and dynamic. The human daily water requirement varies because of differences in body size, dietary solute load, exercise, and activities. Although chronically concentrated urine increases the risk of renal diseases, an empirical method to determine inadequate daily water consumption has not been described for any demographic group; instead, statistical analyses are applied to estimate nutritional guidelines (i.e., adequate intake). This investigation describes a novel empirical method to determine the 24-h total fluid intake (TFI; TFI = water + beverages + moisture in food) and 24-h urine volume, which correspond to inadequate 24-h water intake (defined as urine osmolality of 800 mOsm/kg; U800).

METHODS

Healthy young women (mean ± standard deviation; age, 20 ± 2 y, mass, 60.8 ± 11.7 kg; n = 28) were observed for 7 consecutive days. A 24-h urine sample was analyzed for volume and osmolality. Diet records were analyzed to determine 24-h TFI.

RESULTS

For these 28 healthy young women, the U800 corresponded to a TFI ≥2.4 L/d (≥39 mL/kg/d) and a urine volume ≥1.3 L/d.

CONCLUSIONS

The U800 method could be employed to empirically determine 24-h TFI and 24-h urine volumes that correspond to inadequate water intake in diverse demographic groups, residents of specific geographic regions, and individuals who consume specialized diets or experience large daily water turnover. Because laboratory expertise and instrumentation are required, this technique provides greatest value in research and clinical settings.

Validation of a urine color scale for assessment of urine osmolality in healthy children

AIM

Urine color (UC) is a practical tool for hydration assessment. The technique has been validated in adults, but has not been tested in children.

PURPOSE

The purpose of the study was to test the validity of the urine color scale in young, healthy boys and girls, as a marker of urine concentration, investigate its diagnostic ability of detecting hypohydration and examine the ability of children to self-assess UC.

METHODS

A total of 210 children participated (age: 8-14 years, body mass: 43.4 ± 12.6 kg, height: 1.49 ± 0.13 m, body fat: 25.2 ± 7.8 %). Data collection included: two single urine samples (first morning and before lunch) and 24-h sampling. Hydration status was assessed via urine osmolality (UOsmo) and UC via the eight-point color scale.

RESULTS

Mean UC was 3 ± 1 and UOsmo 686 ± 223 mmol kg(-1). UC displayed a positive relationship as a predictor of UOsmo (R (2): 0.45, P < 0.001). Based on the receiver operating curve, UC has good overall classification ability for the three samples (area under the curve 85-92 %), with good sensitivity (92-98 %) and specificity (55-68 %) for detecting hypohydration. The overall accuracy of the self-assessment of UC in the morning or the noon samples ranged from 67 to 78 %. Further threshold analysis indicated that the optimal self-assessed UC threshold for hypohydration was ≥4.

CONCLUSIONS

The classical eight-point urine color scale is a valid method to assess hydration in children of age 8-14 years, either by researchers or self-assessment.

Twenty-four-hour urine osmolality as a physiological index of adequate water intake

While associations exist between water, hydration, and disease risk, research quantifying the dose-response effect of water on health is limited. Thus, the water intake necessary to maintain optimal hydration from a physiological and health standpoint remains unclear. The aim of this analysis was to derive a 24 h urine osmolality (U_Osm) threshold that would provide an index of “optimal hydration,” sufficient to compensate water losses and also be biologically significant relative to the risk of disease. Ninety-five adults (31.5 ± 4.3 years, 23.2 ± 2.7 kg·m⁻²) collected 24 h urine, provided morning blood samples, and completed food and fluid intake diaries over 3 consecutive weekdays. A U_Osm threshold was derived using 3 approaches, taking into account European dietary reference values for water; total fluid intake, and urine volumes associated with reduced risk for lithiasis and chronic kidney disease and plasma vasopressin concentration. The aggregate of these approaches suggest that a 24 h urine osmolality ≤500 mOsm·kg⁻¹ may be a simple indicator of optimal hydration, representing a total daily fluid intake adequate to compensate for daily losses, ensure urinary output sufficient to reduce the risk of urolithiasis and renal function decline, and avoid elevated plasma vasopressin concentrations mediating the increased antidiuretic effort.

Tapping into water: key considerations for achieving excellence in school drinking water access

OBJECTIVES

We examined free drinking water access in schools.

METHODS

We conducted cross-sectional interviews with administrators from 240 California public schools from May to November 2011 to examine the proportion of schools that met excellent water access criteria (i.e., location, density, type, maintenance, and appeal of water sources), school-level characteristics associated with excellent water access, and barriers to improvements.

RESULTS

No schools met all criteria for excellent water access. High schools and middle schools had lower fountain:student ratios than elementary schools (odds ratio [OR] = 0.06; 95% confidence interval [CI] = 0.02, 0.20; OR = 0.30, 95% CI = 0.12, 0.70). Rural schools were more likely to offer a nonfountain water source than city schools (OR = 5.0; 95% CI = 1.74, 14.70). Newer schools were more likely to maintain water sources than older schools (OR = 0.98; 95% CI = 0.97, 1.00). Schools that offered free water in food service areas increased from pre- to postimplementation of California's school water policy (72%-83%; P < .048). Barriers to improving school water included cost of programs and other pressing concerns.

CONCLUSIONS

Awareness of the benefits related to school drinking water provision and funding may help communities achieve excellence in drinking water access.

Effects of hydration status on cognitive performance and mood

Although it is well known that water is essential for human homeostasis and survival, only recently have we begun to understand its role in the maintenance of brain function. Herein, we integrate emerging evidence regarding the effects of both dehydration and additional acute water consumption on cognition and mood. Current findings in the field suggest that particular cognitive abilities and mood states are positively influenced by water consumption. The impact of dehydration on cognition and mood is particularly relevant for those with poor fluid regulation, such as the elderly and children. We critically review the most recent advances in both behavioural and neuroimaging studies of dehydration and link the findings to the known effects of water on hormonal, neurochemical and vascular functions in an attempt to suggest plausible mechanisms of action. We identify some methodological weaknesses, including inconsistent measurements in cognitive assessment and the lack of objective hydration state measurements as well as gaps in knowledge concerning mediating factors that may influence water intervention effects. Finally, we discuss how future research can best elucidate the role of water in the optimal maintenance of brain health and function.

What is the cell hydration status of healthy children in the USA? Preliminary data on urine osmolality and water intake

OBJECTIVE

Hyperosmotic stress on cells limits many aspects of cell function, metabolism and health. International data suggest that schoolchildren may be at risk of hyperosmotic stress on cells because of suboptimal water intake. The present study explored the cell hydration status of two samples of children in the USA.

DESIGN

Cross-sectional study describing the urine osmolality (an index of hyperosmotic cell shrinkage) and water intake of convenience samples from Los Angeles (LA) and New York City (NYC).

SETTING

Each participant collected a urine sample at an outpatient clinic on the way to school on a weekday morning in spring 2009. Each was instructed to wake, eat, drink and do as usual before school, and complete a dietary record form describing the type and amounts of all foods and beverages consumed after waking, before giving the sample.

SUBJECTS

The children (9-11 years) in LA (n 337) and NYC (n 211) considered themselves healthy enough to go to school on the day they gave the urine sample.

RESULTS

Elevated urine osmolality (>800 mmol/kg) was observed in 63 % and 66 % of participants in LA and NYC, respectively. In multivariable-adjusted logistic regression models, elevated urine osmolality was associated with not reporting intake of drinking water in the morning (LA: OR = 2·1, 95 % CI 1·2, 3·5; NYC: OR = 1·8, 95 % CI 1·0, 3·5). Although over 90 % of both samples had breakfast before giving the urine sample, 75 % did not drink water.

CONCLUSIONS

Research is warranted to confirm these results and pursue their potential health implications.

The Expanding Spectrum of Health Risks: Public Health or Harm?

Drawing on hydration as an illustrative case in point, this review discusses evidence-based perspectives on the continually expanding spectrum of promulgated health risks, including potential benefits and harms to public health. Future directions for inquiry and practice also are addressed.

Dehydration affects brain structure and function in healthy adolescents

It was recently observed that dehydration causes shrinkage of brain tissue and an associated increase in ventricular volume. Negative effects of dehydration on cognitive performance have been shown in some but not all studies, and it has also been reported that an increased perceived effort may be required following dehydration. However, the effects of dehydration on brain function are unknown. We investigated this question using functional magnetic resonance imaging (fMRI) in 10 healthy adolescents (mean age = 16.8, five females). Each subject completed a thermal exercise protocol and nonthermal exercise control condition in a cross-over repeated measures design. Subjects lost more weight via perspiration in the thermal exercise versus the control condition (P < 0.0001), and lateral ventricle enlargement correlated with the reduction in body mass (r = 0.77, P = 0.01). Dehydration following the thermal exercise protocol led to a significantly stronger increase in fronto-parietal blood-oxygen-level-dependent (BOLD) response during an executive function task (Tower of London) than the control condition, whereas cerebral perfusion during rest was not affected. The increase in BOLD response after dehydration was not paralleled by a change in cognitive performance, suggesting an inefficient use of brain metabolic activity following dehydration. This pattern indicates that participants exerted a higher level of neuronal activity in order to achieve the same performance level. Given the limited availability of brain metabolic resources, these findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visuo-spatial processing.