Dehydration is still underappreciated as a cause of hospitalization and mortality in the elderly.  In 1991, 6.7% (731,695) of Medicare hospitalizations had dehydration listed as one of the five reported diagnoses, a rate of 236.2 per 10,000 elderly Medicare beneficiaries. Medicare reimbursed over $446 million for hospitalizations with dehydration as the principal diagnosis.  Older people, men, and African-Americans had elevated risks for hospitalization with dehydration.  About 50% of elderly Medicare beneficiaries hospitalized with dehydration, died within a year of admission [1].

Dehydration increases blood viscosity.  By definition, blood viscosity is a measure of how concentrated the blood is (“hemoconcentration”) and is a measure of hydration status.  A 6-year study of 8,280 men and 12,017 women, initially without heart disease, prior stroke, or diabetes, reported that five or more glasses of water per day were associated with a lower risk of fatal heart disease than two or fewer glasses of water per day [2]. 

Since dehydration increases blood viscosity, which is a root cause of heart disease and stroke, it is important to drink enough water each day.   


Holsworth RE, Cho YI. “Hyperviscosity Syndrome: A Nutritionally-Modifiable Cardiovascular Risk Factor.” Advancing Medicine with Food and Nutrients, Second Edition. Ed. Ingrid Kohlstadt. Boca Raton: CRC Press. 2012.


1. Warren, J. L., et al. The burden and outcomes associated with dehydration among US elderly, 1991. American Journal of Public Health 1994; 84, 1265.

2. Chan, J., et al. Water, other fluids, and fatal coronary heart disease: The Adventist Health Study. Am J Epidemiol 2002; 155 :827–33.

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