Hyponatremia associated with long-term medication use in the elderly: an analysis in general practice.

INTRODUCTION The aim of this study is to determine the prevalence of hyponatremia, its association with long-term medication use and underlying chronic conditions, the rate of hospitalisation and death within 3 months from its discovery and its management in community-dwelling older people. METHODS One year of data for ~5635 patients aged >65 years was extracted from the databases of 19 general practitioners (GPs); 2569 (45.6%) were checked for hyponatremia. RESULTS Hyponatremia occurred in 205 (8.0%) of 2569 checked individuals: 78.5% (161/205) had hypertension, 31.2% (64/205) diabetes, 23.9% (49/205) chronic renal failure; 38.0% (78/205) received diuretics, 36.6% (75/205) renin-angiotensin system antagonists (ACE-I/ARB) and 9.8% (20/205) serotonin reuptake inhibitors. Drug consumption was higher in hyponatremic patients, although only diuretics, ACE-I/ARB, anti-arrhythmics and opioids were significantly associated with hyponatremia. The likelihood of hyponatremia trebled when four drugs were taken, and it was seven-fold higher with the use of six drugs. Hyponatremia was associated with a higher prevalence of chronic illnesses and higher rate of hospitalisation (13.7% vs 7.7%, P = 0.005) and death (3.9% vs 1.8%, P < 0.035). The use of at least one long-term medication was associated with hospitalisation or death in hyponatremic patients (10% vs 6.3%, P = 0.010). Less than 20% of hyponatremic patients had their sodium level checked again after 1 month. DISCUSSION Hyponatremia is not uncommon among community-living older patients, especially in patients taking medications potentially causing hyponatremia. Hyponatremic patients are likely to encounter more serious events, including hospitalisation and death. Targeted training of GPs is desirable to improve their practice.