Low-intake dehydration is a common and often chronic condition in older adults. Adverse health outcomes associated with low-intake dehydration in older adults include poorer cognitive performance, reduced quality of life, worsened course of illness and recovery, and a high number of unplanned hospital admissions and increased mortality. The subjective methods to assess (risk of) dehydration are not reliable, and the evidence about preventive measures are also limited. So is the knowledge about the optimal intake of beverages per day. This narrative review presents the state of the science on the role of low intake hydration in older adults. Despite its simple cause—the inadequate intake of beverages—low-intake dehydration appears to be a very complex problem to address and much more research is needed in the area. Based on the existing evidence, it seems necessary to take setting specific differences and individual problems and needs into account to tackle dehydration in older adults. Further, it is necessary to increase awareness of the prevalence and severity of low-intake dehydration among older adults and in nursing staff in care homes and hospitals as well as among caregivers of older adults living at home.
1. Introduction
Low-intake dehydration is often referred to as hypertonic, hyperosmotic, or water-loss, and describes an uncompensated, predominantly pure water deficit
[1]. Low-intake dehydration is commonly caused by a beverage intake insufficient to compensate potential fluid losses through urine, feces, breath, and/or sweat
[2]. This leads to a concentration of particles within body fluids, a decrease in extracellular fluid volume, and an increase in directly measured serum osmolality
[3].
Low-intake dehydration is a common often chronic health condition in older adults
[1][2][3][1,2,3]. When using the measurement of serum osmolality, several studies have found that the prevalence of low-intake dehydration is lowest among older adults living at home, increased in long-term care residents, and highest in older hospitalized adults
[1][3][4][1,3,4]. The high prevalence of dehydration in long-term care residents has been confirmed in a recent systematic review
[2]. Specifically, dysphagia, which is prevalent in about one in seven nursing home residents
[5], is a major risk factor for poor outcomes including low-intake dehydration
[6]. Regarding the hospital setting, studies with admission data of older patients reflect their increased risk of low-intake dehydration and show increased osmolality in almost 50%
[1]. Unfortunately, data on low-intake dehydration developing during hospitalization are sparse
[4]. However, it has been reported that two-thirds of patients that were dehydrated on admission, were still dehydrated after 48 h
[1].
There are several reasons for a high prevalence of low-intake dehydration among older adults: With age, there is a weakening of physiological mechanisms after insufficient fluid intake that may increase the risk of low-intake dehydration, including a decrease in thirst sensation and primary urine concentration by the kidney
[4]. In addition, total body water decreases with age, resulting in lower fluid stores. This aspect is exacerbated by the frequent use of diuretics and laxatives
[4]. Besides physiological causes, low-intake dehydration in older people can be caused by a range of other risk factors, such as polypharmacy
[7], functional and cognitive impairment
[3][8][3,8], and voluntarily reduced fluid intake: This voluntary reduction can be for a variety of reasons, ranging from the assumption that intake is sufficient for their health to fear of incontinence; social isolation; reduced physical function and access to beverages; as well as swallowing problems and dysphagia
[4].
Adverse health outcomes associated with low-intake dehydration in older adults are multifaceted, ranging from poorer cognitive performance, reduced quality of life, delirium, falls, fractures, worsened course of illness and recovery to heart disease, heat stress, kidney failure, unplanned hospital admissions, and increased mortality
[8][9][8,9]. As low-intake dehydration is associated with poorer health and thus increased medical treatments, it is not surprising that experts agree that low-intake dehydration in older adults entails high costs for the health systems
[9]. Low-intake dehydration and the associated consequences have repeatedly been shown to be a major cause of avoidable hospital admissions in the US and Europe, and it has been estimated that this leads to an economic burden in the US of USD 5.5 billion (in 2004)
[1].
A major problem regarding prevention and tackling of low-intake dehydration in older adults is that assessment methods widespread in clinical practice (e.g., skin turgor, urine color and volume, heart rate, feeling of a dry mouth, thirst sensation) are not reliable
[8]. Some clinical signs associated with low-intake dehydration may be misleading as they can be consequences of other conditions common in this age group. Symptoms like tongue furrows, dry mucous membranes, and urine specific gravity, may indicate low-intake dehydration, but may also be influenced by medications
[10]. Another problem is that the evidence on preventive measures is limited, as is knowledge about the optimal intake of beverages per day for older adults
[4].
These aspects were examined in systematic literature searches for the European Society for Clinical Nutrition and Metabolism (ESPEN) guideline on nutrition and hydration in geriatrics
[4]. This resulted in several evidence-based recommendations focusing on low-intake dehydration. The aim of this narrative review is to present the evidence-based recommendations on low-intake dehydration by ESPEN and based on a literature review, check if new evidence is consistent/inconsistent with the ESPEN recommendations and identify remaining gaps to research on the role of low-intake hydration in older adults.
2. Discussion on Low-Intake Dehydration in Older Adults
The ESPEN guideline on nutrition and hydration in geriatrics, published in 2019, provides evidence-based recommendations and consensus on key issues regarding low-intake dehydration. In this narrative review, we identified 16 new publications mainly in line and supporting the recommendations (see
Table 1). Only one article was contrary to the ESPEN guideline. It can be concluded, that low-intake dehydration in older people is a complex problem to address and the prevalence is still high, although it seems to be a rather simple problem of not drinking enough. Low-intake dehydration is rarely identified and it remains unclear how to best intervene to prevent or treat it.
Table 1. Evidence-based recommendations regarding low-intake dehydration (adapted from
[4]) §).
|
Research Question (RQ) |
Recommendation § |
Grade of Recommendation * |
1 |
How should low-intake dehydration be identified in older persons? (RQ 1.1, 1.2, 1.3) |
An action threshold of directly measured serum osmolality > 300 mOsm/kg should be used to identify low-intake dehydration in older adults |
B |
Where directly measured osmolality is not available then the osmolarity equation (osmolarity = 1.86 × (Na+ + K+) + 1.15 × glucose + urea + 14 (all measured in mmol/L) with an action threshold of >295 mmol/L) should be used to screen for low-intake dehydration in older persons |
A range of appropriate (i.e., hydrating) drinks should be offered to older people according to their preferences |
B |