Distinguishing Low and High Water Consumers-A Paradigm of Disease Risk

Fluid and Electrolyte Disorders in Traumatic Brain Injury: Clinical Implications and Management Strategies

Traumatic brain injuries (TBIs) cause direct central nervous system injury. The presentation depends on the location, the type, and the severity of the injury. Additional injury may develop secondary to compression, the disruption of cerebral perfusion, and changes in sodium levels, resulting in either cellular edema or dehydration. Plasma osmolality (Posm) is a critical parameter influenced by solute concentrations, including sodium, glucose, and urea, and is a relevant concern when considering sodium levels in these patients. While Posm can be calculated using a standard formula, direct measurements via osmometry offer better accuracy. It is essential to differentiate between osmolality and tonicity; the latter refers specifically to effective solutes that drive water movement in the extracellular fluid. Sodium and its anions are effective solutes, whereas urea and glucose have variable effects due to their permeability and insulin dependence. Following TBI, the dysregulation of osmoregulation may occur and affect neurological outcomes. Osmoreceptors in the brain regulate arginine vasopressin secretion in response to changes in effective solute concentrations, with sodium chloride and mannitol being potent stimuli. The regulation of plasma osmolality, typically maintained within ±5% of the 280-295 mOsm/kg H2O range, is crucial for homeostasis and relies on antidiuresis and thirst mechanisms. This review narrative underscores the complexities of osmoregulation in the context of TBIs and their clinical implications, particularly concerning the development of conditions such as diabetes insipidus, the syndrome of inappropriate antidiuretic hormone secretion, and abnormal thirst.

Assessment of exercise-induced dehydration in underhydrated athletes: Which method shows the most promise?

BACKGROUND & AIMS

Athletes are commonly exposed to exercise-induced dehydration. However, the best method to detect dehydration under this circumstance is not clear. This study aimed to analyze pre- and post-dehydration measurements of biomarkers, including saliva osmolality (SOsm), urine osmolality (UOsm), urine-specific gravity (USG), urine color (Ucolor), serum osmolality (SeOsm), serum arginine vasopressin (AVP), serum sodium (Na+), and thirst sensation in underhydrated athletes, using the body mass loss (BML) as the reference method.

METHODS

In this clinical trial (NCT05380089), a total of 38 athletes (17 females) with a regular low water intake (<35 mL/kg/day) were submitted to exercise-induced dehydration with a heat index of 29.8 ± 3.1 °C and an individualized running intensity (80-90% of first ventilatory threshold).

RESULTS

ROC curve analysis revealed significant discriminative abilities of SOsm, with AUC values of 0.76 at 1.5% BML, 0.75 at 1.75% BML, and 0.87 at 2% BML, while Na+ and SeOsm showed the highest AUC of 0.87 and 0.91 at 2% BML, respectively. SOsm showed high sensitivity at 1.5% of BML, while SeOsm and Na+ demonstrated high sensitivity at 2% of BML.

CONCLUSION

This study highlights SOsm as a potential indicator of hydration status across different levels of BML. Additionally, Na+ and SeOsm emerged as accurate dehydration predictors at 1.75% and 2% of BML. Notably, the accuracy of urinary indices and thirst sensation for detecting hydration may be limited.

Low daily water intake profile-is it a contributor to disease?

Few previous review articles have focused on the associations between inadequate daily water intake (LOW) or urinary biomarkers of dehydration (UD; low urine volume or high urine osmolality) and multiple diseases. Accordingly, we conducted manual online searches (47 key words) of the PubMed, Embase, and Google Scholar databases with these inclusion criteria: English language, full-text, peer reviewed, no restriction on research design, and three publications minimum. Initially, 3,903 articles were identified based on their titles and abstracts. Evaluations of full length .pdf versions identified 96 studies that were acceptable for inclusion. We concluded that the evidence is insufficient or conflicting for seven disorders or diseases (i.e. suggesting the need for additional clarifying research) and it is lacking for all-cause mortality. Differential characterizations among women and men have been reported in the results of nine studies involving five diseases. Finally, the evidence for associations of LOW or UD is strong for both kidney stones and type 2 diabetes with hyperglycemia. This suggests that great public health value (i.e. reduced disease risk) may result from increased daily water intake-a simple and cost-effective dietary modification.

Sequential recruitment of body fluid spaces for increasing volumes of crystalloid fluid

Introduction

The interstitial space harbours two fluid compartments linked serially to the plasma. This study explores conditions that lead to fluid accumulation in the most secluded compartment, termed the "third space".

Methods

Retrospective data was collected from 326 experiments in which intravenous crystalloid fluid was administered to conscious volunteers as well as a small group of anaesthetized patients. The urinary excretion and plasma dilution derived from haemoglobin served as input variables in nine population volume kinetic analyses representing subtly different settings.

Results

An infusion of 250-500 mL of Ringer's solution expanded only the central fluid space (plasma), whereas the infusion of 500-1,000 mL extended into a rapidly exchanging interstitial fluid space. When more than 1 L was infused over 30 min, it was distributed across plasma and both interstitial fluid compartments. The remote space, characterized by slow turnover, abruptly accommodated fluid upon accumulation of 700-800 mL in the rapidly exchanging space, equivalent to an 11%-13% volume increase. However, larger expansion was necessary to trigger this event in a perioperative setting. The plasma half-life of crystalloid fluid was 25 times longer when 2,000-2,700 mL expanded all three fluid compartments compared to when only 250-500 mL expanded the central space (14 h versus 30 min).

Conclusion

As the volume of crystalloid fluid increases, it apparently occupies a larger proportion of the interstitial space. When more than 1 L is administered at a high rate, there is expansion of a remote "third space", which considerably extends the intravascular half-life.

Characterizing dehydration in short-term spaceflight using evidence from Project Mercury

Short-term spaceflight is commonly perceived as posing minimal risk to human health and performance. However, despite their duration, short-term flights potentially induce acute physiological changes that create risk to crews. One such change is dehydration (primarily body water loss) due to a heat-stressed environment. Such loss, if severe and prolonged, can lead to decrements in performance as well as increase the risk of more serious medical conditions. Though the general mechanisms of dehydration are broadly understood, the rate and extent of dehydration in short-term spaceflight has not been characterized. Combining data from the six spaceflights of the US Mercury program with a causal diagram illustrating the mechanisms of dehydration, we fit a path model to estimate the causal effects for all pathways in the causal model. Results demonstrate that Mercury astronauts experienced some degree of dehydration across the range of suited time and that the relationship between suited time and dehydration appears to be logarithmic. We discuss causal interpretations of the results and how the results from this and similar analyses can inform countermeasure development for short-term spaceflight.

H2OAthletes study protocol: effects of hydration changes on neuromuscular function in athletes

We aim to understand the effects of hydration changes on athletes' neuromuscular performance, on body water compartments, fat-free mass hydration and hydration biomarkers and to test the effects of the intervention on the response of acute dehydration in the hydration indexes. The H2OAthletes study (clinicaltrials.gov ID: NCT05380089) is a randomised controlled trial in thirty-eight national/international athletes of both sexes with low total water intake (WI) (i.e. < 35·0 ml/kg/d). In the intervention, participants will be randomly assigned to the control (CG, n 19) or experimental group (EG, n 19). During the 4-day intervention, WI will be maintained in the CG and increased in the EG (i.e. > 45·0 ml/kg/d). Exercise-induced dehydration protocols with thermal stress will be performed before and after the intervention. Neuromuscular performance (knee extension/flexion with electromyography and handgrip), hydration indexes (serum, urine and saliva osmolality), body water compartments and water flux (dilution techniques, body composition (four-compartment model) and biochemical parameters (vasopressin and Na) will be evaluated. This trial will provide novel evidence about the effects of hydration changes on neuromuscular function and hydration status in athletes with low WI, providing useful information for athletes and sports-related professionals aiming to improve athletic performance.

Long-term health outcomes associated with hydration status

Body water balance is determined by fundamental homeostatic mechanisms that maintain stable volume, osmolality and the composition of extracellular and intracellular fluids. Water balance is maintained by multiple mechanisms that continuously match water losses through urine, the skin, the gastrointestinal tract and respiration with water gains achieved through drinking, eating and metabolic water production. Hydration status is determined by the state of the water balance. Underhydration occurs when a decrease in body water availability, due to high losses or low gains, stimulates adaptive responses within the water balance network that are aimed at decreasing losses and increasing gains. This stimulation is also accompanied by cardiovascular adjustments. Epidemiological and experimental studies have linked markers of low fluid intake and underhydration - such as increased plasma concentration of vasopressin and sodium, as well as elevated urine osmolality - with an increased risk of new-onset chronic diseases, accelerated aging and premature mortality, suggesting that persistent activation of adaptive responses may be detrimental to long-term health outcomes. The causative nature of these associations is currently being tested in interventional trials. Understanding of the physiological responses to underhydration may help to identify possible mechanisms that underlie potential adverse, long-term effects of underhydration and inform future research to develop preventative and treatment approaches to the optimization of hydration status.

Every sip counts: Understanding hydration behaviors and user-acceptability of digital tools to promote adequate intake during early and late pregnancy

Maintaining adequate hydration over the course of pregnancy is critical for maternal and fetal health and reducing risks for adverse pregnancy outcomes (e.g., preeclampsia, low placental and amniotic fluid volume). Recent evidence suggests that women may be at risk for under-hydration in the second and third trimesters when water needs begin to increase. Scant research has examined pregnant women's knowledge of hydration recommendations, water intake behaviors, and willingness to use digital tools to promote water intake. This study aimed to: 1) describe hydration recommendation knowledge and behaviors by the overall sample and early vs late pregnancy, and 2) identify habits and barriers of using digital tools. Pregnant women (N = 137; M age = 30.9 years; M gestational age = 20.9) completed a one-time, 45-minute online survey. Descriptive statistics quantified women's knowledge of hydration recommendations, behaviors, and attitudes about utilizing digital tools to promote adequate intake, and Mann-Whitney U and chi-squared tests were used to determine group differences. Most women lacked knowledge of and were not meeting hydration recommendations (63%, 67%, respectively) and were not tracking their fluid consumption (59%). Knowledge of hydration recommendations differed by time of pregnancy, such that women in later pregnancy reported 82 ounces compared to women in early pregnancy (49 ounces). Common barriers included: forgetting to drink (47%), not feeling thirsty (47%), and increased urination (33%). Most were willing to use digital tools (69%) and believed a smart water bottle would help them achieve daily fluid recommendations (67%). These initial findings suggest that pregnant women may benefit from useful strategies to increase knowledge, decrease barriers, and maintain adequate hydration, specifically earlier in pregnancy. These findings will inform the design of a behavioral intervention incorporating smart connected water bottles, wearables for gesture detection, and behavior modification strategies to overcome barriers, promote proper hydration and examine its impact on maternal and infant health outcomes.

Detection of low urine output by measuring urinary biomarkers

BACKGROUND

Urine output < 1 L per 24 h is a clinical warning sign that requires attention from hospital staff, who should determine whether the low flow is due to low habitual intake of water or disease-induced dehydration. The incidence of this condition is unclear.

METHODS

A cohort of 20 healthy volunteers (mean age 42 years, range 23-62 years) recorded their food and water intakes daily for 8 days. They also collected and measured all urine and delivered first morning urine samples for analysis of osmolality and creatinine. Optimal cutoffs for these biomarkers to indicate urine output of < 1 L or 15 mL/kg during the preceding 24 h were applied with and without correction for age to cross-sectional data from 1,316 subjects in various clinical settings, including healthy volunteers, preoperative patients, patients seeking acute care at a hospital, and patients receiving institutional geriatric care.

RESULTS

The urine output amounted to < 1 L during 22 of the 159 evaluable study days and was indicated by urine osmolality > 760 mosmol/kg or urine creatinine > 13 mmol/L, which had sensitivity and specificity of approximately 80%. Days with urine output < 1 L were associated with significantly less intake of both water (-41%) and calories (-22%) compared to other days. Application of age-corrected biomarker cutoffs to the 1,316 subjects showed a stronger dependency of low urine output on age than the clinical setting, occurring in 44% of the 72 participants aged 15-30 years and 18% of the 62 patients aged 90-104 years.

CONCLUSION

Biomarkers measured in morning urine of young and middle-aged volunteers indicated urine output of < 1 L with good precision, but the cutoffs should be validated in older age groups to yield reliable results.

TRIAL REGISTRATIONS

ISRCTN12215472 at http://www.isrctn.com ; NCT01458678 at ClinicalTrials.gov, and ChiCTR-TNRC-14,004,479 at the chictr.org/en.

Association between plain water intake and risk of hypertension: longitudinal analyses from the China Health and Nutrition Survey

Objective

This study aimed to investigate the prospective association between plain water intake and the risk of hypertension based on a longitudinal cohort study in China.

Methods

Logistic regression analyses were performed to investigate the association between plain water intake and hypertension. Restricted cubic spline model was use to evaluate non-linear relationship between plain water intake and hypertension. Subgroup analyses and interaction tests were conducted based on age, gender, residence site, educational level and tea consumption.

Results

A total of 3,823 participants (46.5% male) with a mean age of 46.8 years from the China Health and Nutrition Survey (CHNS) were assessed and divided into 4 groups based on plain water intake. There was a decreasing trend of hypertension risk as plain water intake increased. Logistic regression analyses indicated that participants consuming plain water ≥6 cups/day (1 cup ≈ 240 mL) had significantly lower risk of hypertension compared to those consuming ≤1 cup/day, even after adjustments for covariates. Restricted cubic spline curve revealed that participants consuming about 6-8 cups/day were at lower risk for developing hypertension. In subgroup analyses, the results were generally consistent with the main findings in participants who aged less than 60 years, who were male, who attained higher education and who were low tea consumers.

Conclusion

Our findings suggested that there might be a favorable effect of plain water intake on preventing hypertension in a large cohort of Chinese adults from the general population. Drinking adequate amounts of plain water (about 6-8 cups/day) may reduce the risk of hypertension, particularly in the selected population. Further interventional studies are required to investigate the potential effect of increasing plain water intake on blood pressure regulation.

Healthy eating behaviors and food consumption frequencies of retail workers

BACKGROUND

Retail workers comprise millions of people, but little is known about their eating behaviors and food consumption patterns.

OBJECTIVE

To examine the healthy eating behaviors and food consumption frequencies of retail workers in shopping malls.

METHODS

The sample of this descriptive study consisted of 385 retail employees working in ready-made garment stores of shopping malls in Istanbul (42% of those eligible). A descriptive information form, the nutrition subscale of the Health-promoting Lifestyle Profile (HPLP), and the Food Consumption Frequency Survey were used as data collection tools.

RESULTS

It was determined that more than half of the participants skipped breakfast and other meals and consumed fast food and packaged and acidic drinks five to six days a week. The mean score of the participants on the HPLP-nutrition subscale was determined to be 11.79±3.29.

CONCLUSIONS

The retail workers in shopping malls were found to have insufficient healthy eating behaviors, a low frequency of healthy food consumption, and a high level of fast-food consumption. Maintaining healthy eating habits is crucial for the health of employees. It is necessary for workplaces to take steps to help their employees become aware of and practice healthy eating. Workplaces should also be encouraged to provide healthy food options for their employees.

Athletes with different habitual fluid intakes differ in hydration status but not in body water compartments

Physiological differences have been reported between individuals who have habitual low (LOW) and high (HIGH) water intake (WI). The aims of this study were to explore body water compartments, hydration status, and fat-free mass (FFM) hydration of elite athletes exposed to different habitual WI. A total of 68 athletes (20.6 ± 5.3 years, 23 females) participated in this observational cross-sectional study. Total WI was assessed by seven-day food diaries and through WI, athletes were categorized as HIGH (n = 28, WI≥40.0 mL/kg/d) and LOW (n = 40, WI≤35.0 mL/kg/d). Total body water (TBW) and extracellular water (ECW) were determined by dilution techniques and intracellular water (ICW) as TBW-ECW. Hydration status was assessed by urine-specific gravity (USG) using a refractometer. Fat (FM) and FFM were assessed by dual-energy X-ray absorptiometry (DXA). The FFM hydration was calculated by TBW/FFM. The USG was statistically different between groups for females (LOW: 1.024 ± 0.003; HIGH: 1.015 ± 0.006; p = 0.005) and males (LOW: 1.024 ± 0.002; HIGH: 1.018 ± 0.005; p < 0.001). No differences between groups were detected in body water compartments and FFM hydration in both sexes (p > 0.05). Multiple regression showed that WI remains a predictor of USG regardless of FFM, age, and sex (β = -0.0004, p < 0.01). We concluded that LOW athletes were classified as dehydrated through USG although their water compartments were not different from HIGH athletes. These results suggest that LOW athletes may expectedly maintain the body water compartments' homeostasis through endocrine mechanisms. Interventions should be taken to encourage athletes to have sufficient WI to maintain optimal hydration.

Hydration Status in Older Adults: Current Knowledge and Future Challenges

Adequate hydration is essential for the maintenance of health and physiological functions in humans. However, many older adults do not maintain adequate hydration, which is under-recognized and poorly managed. Older adults are more vulnerable to dehydration, especially those living with multiple chronic diseases. Dehydration is associated with adverse health outcomes in older adults, and acts as an independent factor of the hospital length of stay, readmission, intensive care, in-hospital mortality, and poor prognosis. Dehydration is a prevalent health problem in older adults, accounting for substantial economic and social burden. This review attempts to provide current knowledge of hydration including patterns of body water turnover, the complex mechanisms behind water homeostasis, the effects of dehydration on the health of the body, and practical guidance for low-intake dehydration in older adults.

HISTOULTRASTRUCTURAL FEATURES OF THYMOCYTES DUE TO THE IMPACT OF THE EXPERIMENTAL GENERAL DEHYDRATION OF A MILD DEGREE

OBJECTIVE

The aim: The objective of the current study was to reveal ultrastructural changes in rats' thymocytes in experimental data in conditions of mild general dehydration.

PATIENTS AND METHODS

Materials and methods: The study was conducted on 20 non-linear adult male laboratory rats weighing 150-170 g. Histological and semi-thin slides of the thymus were prepared according to the required guidelines.

RESULTS

Results: On average, in the cortical zone of the thymus, there was decreased cellularity by 13.4% (p<0.001), while in the medulla zone this indicator turned out to be unreliable - 5.5% (р=0.19), compared to the indicators in animals of the control group. The study showed that a slight degree of general dehydration of the body causes ultrastructural changes in the thymus and is accompanied by a cell-mediated response of the central link of immunogenesis and results in morphological changes in the thymus, which are atrophic in nature with a typical pattern of remodeling of the organ's microstructure, which corresponds to cellular aging and the associated sign of accelerated involution.

CONCLUSION

Conclusions: General dehydration of a mild degree in the experiment is accompanied by a cell-mediated response of the central link of immunogenesis and results in morphological changes in the thymus, which are atrophic in nature with a typical pattern of remodeling of the organ's microstructure, which corresponds to cellular aging and the associated sign of accelerated involution.

Association Between Serum Creatinine Concentrations and Overall Survival in Patients With Colorectal Cancer: A Multi-Center Cohort Study

Background

Colorectal cancer (CRC) is one of the most common malignancies throughout the world, with high rates of morbidity and mortality. Previous studies reported that serum creatinine (Scr) concentrations were associated with overall survival (OS) in cancer patients, but little is known about the association between Scr and OS in patients with CRC. This study investigated the relationship between Scr concentrations and OS in patients with CRC and examined possible effect modifiers.

Methods

A retrospective cohort, including 1,733 patients with CRC, was established from a multi-center clinical study. Patients were divided into low (<71 μmol/L in men or <59 μmol/L in women), normal (71-104 μmol/L in men or 59-85 μmol/L in women) and high (>104 μmol/L in men or >85 μmol/L in women) Scr groups. Cox regression analysis was used to examine association between Scr concentrations and OS. Stratified (subgroup) analyses were used to examine men and women separately. Interaction tests were used to evaluate associations between each variable and OS, as well as possible interactions of these variables with Scr levels. Cross-classified analyses were used only in men.

Results

Patients with low [hazard ratio (HR) = 1.43, 95% confidence interval (CI) = 1.19-1.72; P < 0.001] or high (HR = 1.89, 95% CI = 1.36-2.63; P < 0.001) Scr level had a significantly lower OS than patients with normal Scr levels. Significant interactions with Scr concentrations were observed for body mass index (P for interaction = 0.019) in men.

Conclusion

Low or high Scr concentration is associated with significantly lower OS in patients with CRC. Future study is warranted to investigate the underlying mechanism.

Estimates of fluid intake, urine output and hydration-levels in women from Somaliland: a cross-sectional study

The study objective was to measure fluid intake and associations with background characteristics and hydration biomarkers in healthy, free-living, non-pregnant women aged 15–69 years from Hargeisa city. We also wanted to estimate the proportion of euhydrated participants and corresponding biomarker cut-off values. Data from 136 women, collected through diaries and questionnaires, 24h urine samples and anthropometric measurements, were obtained with a cross-sectional, purposeful sampling from fifty-two school and health clusters, representing approximately 2250 women. The mean (95 % CI) 24 h total fluid intake (TFI) for all women was 2⋅04 (1⋅88, 2⋅20) litres. In multivariate regression with weight, age, parity and a chronic health problem, only weight remained a predictor (P 0.034, B 0.0156 (l/kg)). Pure water, Somali tea and juice from powder and syrup represented 49⋅3, 24⋅6 and 11⋅7 % of TFI throughout the year, respectively. Mean (95 % CI) 24 h urine volume (Uvol) was 1⋅28 (1⋅17, 1⋅39) litres. TFI correlated strongly with 24 h urine units (r 0.67) and Uvol (r 0.59). Approximately 40 % of the women showed inadequate hydration, using a threshold of urine specific gravity (Usg) of 1⋅013 and urine colour (Ucol) of 4. Five percent had Usg > 1⋅020 and concomitant Ucol > 6, indicating dehydration. TFI lower cut-offs for euhydrated, non-breast-feeding women were 1⋅77 litres and for breast-feeding, 2⋅13 litres. Euhydration cut-off for Uvol was 0⋅95 litre, equalling 9⋅2 urine units. With the knowledge of adverse health effects of habitual hypohydration, Somaliland women should be encouraged to a higher fluid intake.

Secondhand smoke increases the risk of developing kidney stone disease

Research indicates smoking increases the risk of various kidney diseases, although the risk of developing kidney stone disease in non-smokers exposed to secondhand smoke is unknown. This study analyzed a total of 19,430 never-smokers with no history of kidney stone disease who participated in the Taiwan Biobank from 2008 to 2019. They were divided into two groups by secondhand smoke exposure; no exposure and exposure groups; the mean age of participants was 51 years, and 81% were women. Incident kidney stone development was observed in 352 (2.0%) and 50 (3.3%) participants in the no exposure and exposure groups during a mean follow-up of 47 months. The odds ratio (OR) of incident kidney stone was significantly higher in the exposure group than the no exposure group [OR, 1.64; 95% confidence interval (95% CI) 1.21 to 2.23]. Participants with > 1.2 h per week exposure were associated with almost twofold risk of developing kidney stones compared with no exposure (OR, 1.92; 95% CI 1.29 to 2.86). Our study suggests that secondhand smoke is a risk factor for development of kidney stones and supports the need for a prospective evaluation of this finding.

Development and validation of a new nursing diagnosis: Perioperative thirst

PURPOSE

To develop and validate the content of the nursing diagnosis proposal for perioperative thirst.

METHODS

A content analysis by 34 judges. An online Delphi panel was used in one round, evaluating criteria of relevance, clarity and precision. Wilcoxon's one-tailed test was used and the content validity index to maintain the item was set to 0.80.

FINDINGS

The content validity index in relation to the evaluated items reached levels between 0.87-1.00. The final components of the diagnosis proposal included the following items as defining characteristics: dry mouth, dry throat, dry lips, thick saliva, thick tongue, constant swallowing of saliva, desire to drink water, bad taste in the mouth, and caregiver's report. Related factors are as follows: pre- and postoperative fasting, oral breathing, dehydration, hypovolemia, insensitive loss of hydration by breathing, dry mouth, habit of drinking water, high room temperature. Associated conditions: intubation, use of muscarinic and nicotinic anticholinergics and water restriction.

CONCLUSIONS

All components of the nursing diagnosis were validated in relation to relevance, clarity, and accuracy, demonstrating high levels of agreement between experts. Qualitative observations were found to be fundamental for both combining and excluding some items.

IMPLICATIONS FOR NURSING PRACTICE

Improvement of refinement and clarity levels of this nursing diagnosis proposal aiding its inclusion in the NANDA International taxonomy and thus enabling greater understanding of the phenomenon of thirst in surgical patients. This study helps to explain and facilitate the identification of defining characteristics, related factors, and associated conditions for nurses, nursing students, and researchers on this subject.

Rehydration during Endurance Exercise: Challenges, Research, Options, Methods

During endurance exercise, two problems arise from disturbed fluid-electrolyte balance: dehydration and overhydration. The former involves water and sodium losses in sweat and urine that are incompletely replaced, whereas the latter involves excessive consumption and retention of dilute fluids. When experienced at low levels, both dehydration and overhydration have minor or no performance effects and symptoms of illness, but when experienced at moderate-to-severe levels they degrade exercise performance and/or may lead to hydration-related illnesses including hyponatremia (low serum sodium concentration). Therefore, the present review article presents (a) relevant research observations and consensus statements of professional organizations, (b) 5 rehydration methods in which pre-race planning ranges from no advanced action to determination of sweat rate during a field simulation, and (c) 9 rehydration recommendations that are relevant to endurance activities. With this information, each athlete can select the rehydration method that best allows her/him to achieve a hydration middle ground between dehydration and overhydration, to optimize physical performance, and reduce the risk of illness.

Chronic Dehydration in Nursing Home Residents

Chronic dehydration mainly occurs due to insufficient fluid intake over a lengthy period of time, and nursing home residents are thought to be at high risk for chronic dehydration. However, few studies have investigated chronic dehydration, and new diagnostic methods are needed. Therefore, in this study, we aimed to identify risk factors for chronic dehydration by measuring serum osmolality in nursing home residents and also to evaluate whether examining the inferior vena cava (IVC) and determining the IVC collapsibility index (IVC-CI) by ultrasound can be helpful in the diagnosis of chronic dehydration. A total of 108 Japanese nursing home residents aged ≥65 years were recruited. IVC measurement was performed using a portable handheld ultrasound device. Fifteen residents (16.9%) were classified as having chronic dehydration (serum osmolality ≥295 mOsm/kg). Multivariate logistic regression analysis showed that chronic dehydration was associated with dementia (odds ratio (OR), 6.290; 95% confidential interval (CI), 1.270–31.154) and higher BMI (OR, 1.471; 95% CI, 1.105–1.958) but not with IVC or IVC-CI. Cognitive function and body weight of residents should be considered when establishing a strategy for preventing chronic dehydration in nursing homes.

Fluid Intake Recommendation Considering the Physiological Adaptations of Adults Over 65 Years: A Critical Review

The aim of this critical review was to clarify recommended fluid intake for older people. A literature search of published articles and guidelines on fluid intake recommendations until April 2020 was carried out using PUBMED, Scopus, Cochrane, and Google Scholar. In this review, we focused on people over 65 years old at different care levels. The results show that the mean fluid intake ranges between 311 and 2390 mL/day. However, it is difficult to know whether this corresponds to the real pattern of fluid intake, due to the variability of data collection methods. With respect to the recommendations, most international organizations do not take into consideration the physiology of ageing or the health problems associated with an older population. In conclusions, we recommend to follow the guideline of the European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Food Safety Authority (EFSA). ESPEN is the only guideline which takes into account age. It is also based on EFSA recommendations. This authority takes into consideration all fluids consumed (ranging from food to fluids). If it is known that around 20% of all fluids consumed come from food, the result would effectively be that the EFSA recommends the same as the ESPEN guidelines: 1.6 L/day for females and 2.0 L/day for males. The findings could help raise the awareness of professionals in the sector with respect to the required fluid intake of the elderly and, in this way, contribute to avoiding the consequences of dehydration.