You are here
Dehydration and Chronic Disease
Chronic dehydration and low fluid intake have been linked to numerous conditions such as hypertension, cardiovascular disease, asthma, glaucoma, constipation, and arthritis-related pain, among others.1-3 Elderly populations, already prone to chronic diseases, are at increased risk for dehydration due bodily changes and factors such as impaired ability to conserve water, decreased body water with age, reduced sensation of thirst, physical limitations, and medication use.4
According to the 2004 National Hospital Discharge Survey, the overall cost of hospitalization for dehydration in the United States was $5.5 billion.5 Approximately 518,000 hospitalizations in 2004 were for dehydration, and nearly 2% of these admissions died at the hospital. An earlier study of United States Medicare records from 1991 showed an 18% mortality rate of patients within 30 days of hospital admission with dehydration.6 Within a year of hospitalization, about half of those with a principal diagnosis of dehydration died.
Dehydration Thickens the Blood
The role of blood viscosity in the pathogenesis of cardiovascular and cerebrovascular diseases has gained clinical interest in recent years.7-9 It is intuitive and nearly self-evident that when blood loses water, the blood necessarily becomes thicker and less able to flow normally.
Dehydration has been shown to contribute to elevated blood viscosity and may help explain the increased susceptibility of elderly populations to cardiac events in the presence of extreme high or low temperatures. In fact, elderly people are less able to adjust to increased blood viscosity caused by hot temperatures (as a result of sweating) and cold temperatures (impaired vasoconstriction and hemoconcentration from fluid shifts), making them more susceptible to cardiovascular accidents.10
Dehydration, Blood Viscosity, and the Brain
Increased blood viscosity can result in decreased cerebral blood flow and metabolism, a possible mechanism contributing to cognitive impairment in elderly populations with hypertension.11 Mild dehydration has also been associated with deleterious effects on attention, declarative memory, and psychomotor processing speed.12 In such cases, dehydration-induced blood viscosity abnormalities may be contributing to cognitive decline be reducing cerebral blood flow.
The THIRST study retrospectively compared patients with cerebral ischemic events to healthy controls.13 The study showed that elderly patients presenting with transient ischemic attack or acute ischemic stroke often had increased plasma osmolality, an indicator of dehydration. The researchers credited the increased osmolality as a contributing factor to the event rather than a result of neurological deterioration. They followed by suggesting an increase in blood viscosity, as a direct result of dehydration and high osmolality, to be a likely mechanism for the cerebral ischemic events.
7. Lee AJ, Mowbray PI, Lowe GD, Rumley A, Fowkes FG, Allan PL. Blood viscosity and elevated carotid intima-media thickness in men and women: the Edinburgh Artery Study. Circulation. Apr 21 1998;97(15):1467-1473.
9. Cecchi E, Liotta AA, Gori AM, et al. Relationship between blood viscosity and infarct size in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention. Int J Cardiol. May 15 2009;134(2):189-194.