[Hyponatremia in the elderly: its role in frailty]

Hyponatremia is the most common electrolyte disorder in elderly patients. The incidence is about 7% in elderly healthy people but can exceed 40% in hospitalized patients. Considering all its aetiologies hyponatremia is associated with increased mortality and appears as a factor of poor prognosis. Alteration in the regulation of water homeostasis in the elderly result from multiple consequence of aging: change in body composition, alteration in renal function and hormonal changes. The high frequency of nutritional problems, particularly protein malnutrition predisposes the elderly to the development of hyponatremia. Although diuretics especially thiazides are implicated as a frequent cause of hyponatremia on geriatric medicine, normovolemic hyponatremia and more particularly the syndrome of inappropriate antidiuresis is the most common cause. The aetiology of this syndrome can be determined in only approximately half of the cases. Cancers and medications, principally psychotropic agents commonly prescribed in geriatrics are the most frequent aetiologies. Hyponatremia could be a factor of frailty in geriatrics. Mild to moderate hyponatremia is generally considered asymptomatic but recent studies reported that asymptomatic hyponatremia contributes to neurological troubles like cognitive disorders, posture and gait impairments. Hyponatremia could be an independent risk factor of falls and could be associated with the development of osteoporosis. This review of the literature emphasizes the importance of screening and a systematic management of hyponatremia in the elderly people, even in the minor forms and those considered as asymptomatic.