RESPONSE LETTER TO DR. HOYLE ET AL.

Abstract

To the Editor: Hoyle et al. properly note that hyponatremia is a common finding in hospitalized elderly persons. They further raise the possibility that hyponatremia may be more common at the present time than in the past. In their letter to the editor, they report an 18% prevalence of hyponatremia (serum sodium concentration <135 mmol/L) in 103 elderly patients, mean age 82, who were admitted to a hospital geriatric assessment ward. An additional 24% became hyponatremic during the period of hospitalization. They state that this is a higher prevalence than previously reported and wonder whether it might be due to the increased use of medications such as thiazide diuretics, selective serotonin reuptake inhibitors, and angiotensin-converting enzyme inhibitors. Their data are similar to what this author has reported in the past in nursing home residents: 18% cross-sectional incidence and 53% total prevalence during a 12-month period of observation.1 Several other studies of elderly patients admitted to acute or chronic care hospitals have also reported a prevalence of hyponatremia ranging from 11% to 22%.2,3 These observations indicate that the prevalence of hyponatremia in elderly patients has not changed significantly in recent years but rather that it can be found if such patients are properly evaluated. The frequent finding of hyponatremia in hospitalized elderly patients likely is related to interaction between altered physiology of water regulatory systems that occurs as part of the normal aging process and the large number of diseases and drugs that have the potential to affect sodium and water balance in older people.4 The question remains as to what the clinical significance is of hyponatremia itself in the elderly patient, independent of the disease or drug that may be responsible for development of hyponatremia, especially in those with previously existing cognitive impairment. Financial Disclosure: None. Author Contributions: Dr. Miller is responsible for the entire contents of this letter. Sponsor's Role: Not applicable.