Sodium and potassium disturbances in the elderly : prevalence and association with drug use.

OBJECTIVE

To study the incidence of sodium and potassium disturbances in a population of the very old elderly, with respect to medication with potential effects on electrolyte levels.

DESIGN AND SETTING

Cross-sectional study of subjects aged >/=75 years, based on data from the Kungsholmen project, a population-based study of elderly in an urban area of Stockholm, Sweden.

STUDY PARTICIPANTS

1558 elderly individuals (1178 women and 380 men), mean age 81.4 years, providing information about drug use and serum electrolyte data.

MAIN OUTCOME MEASURES

Data on drug use was based on personal interviews. Hyponatraemia was defined as a serum sodium concentration <136 mmol/L, hypernatraemia as a serum sodium concentration >146 mmol/L, hypokalaemia as a serum potassium concentration <3.5 mmol/L and hyperkalaemia as a serum potassium concentration >5.0 mmol/L.

RESULTS

Hyponatraemia was found in 147 subjects (9.4% of the study population) and hypernatraemia in five individuals (0.3%). Hypokalaemia was found in 39 (2.5%) and hyperkalaemia in 43 (2.8%) of the subjects. The prevalence of hyponatraemia (p < 0.001), hypokalaemia (p < 0.05) and hyperkalaemia (p < 0.05) increased with age. Hyponatraemia was found more often in women than in men (p < 0.05). Hypernatraemia was more frequent in subjects who lived in institutions (p < 0.001). The occurrence of hyponatraemia was associated with the use of carbamazepine, laxatives (enema), diuretics and ACE-inhibitors; hypernatraemia was associated with osmotically active laxatives. Hypokalaemia was associated with thiazide-related and combination diuretics; and hyperkalaemia was associated with potassium-sparing diuretics, beta-blockers, cytostatic drugs and tricyclic antidepressants.

CONCLUSIONS

The present study demonstrated the association between electrolyte level disturbances and several types of drugs in a population of the very old elderly. Our results underline the importance of monitoring serum electrolyte levels in the elderly, not only in relation to the use of diuretics, but also several other drugs.