A comparative study of the syndrome of inappropriate antidiuretic hormone secretion in community-dwelling patients and nursing home residents

Background and aims: Limited data exist about the clinical characteristics of the syndrome of inappropriate antidiuretic hormone secretion (SIADHS) in hospitalized elderly. Moreover, there may be differences regarding this syndrome between populations, depending on the referral source to hospitals. The objectives of the study were to determine the etiology, clinical characteristics and hospital outcome in a sample of elderly hospitalized patients with SIADHS, and to compare community-dwelling patients (CDP) with nursing home residents (NHR). Methods: This retrospective chart analysis was conducted in a university affiliated referral hospital. The participants were consecutive elderly patients, admitted with hyponatremia (<135 mmol/L , and ultimately diagnosed as having SIADHS. We examined patient demographics, medical history, clinical presentation, laboratory and imaging studies, and hospital outcome. Results: Of the 179 patients presenting with hyponatremia, 79 patients (44%) fulfilled the criteria for SIADHS; 73% of these patients were CDP and 27% were NHR (mean ages, 74.4±6.9 and 75.7±7.2 years, respectively). Most CDP complained of weakness and dizziness, while NHP presented with confusion, seizures and vomiting. Mean sodium levels and mean plasma osmolality values were similar in both groups, however, the number of patients with sodium levels ≤121 mmol/L was significantly higher among NHR. The leading causes of SIADHS in both groups were medications, idiopathic form, and concurrent malignancies. In patients older than 81 years, idiopathic (50%) and drug-induced (20%) SIADHS were more frequent, compared with younger age groups. The overall in-hospital mortality rate was significantly higher in NHR as compared with CDP (p=0.014), yet, it was similar in both groups once only patients with sodium levels of 121 mmol/L or lower were considered. Conclusions: While leading causes of SIADHS in community and nursing home residents are similar, there are marked differences in clinical presentation and outcome. This knowledge should help in identifying high-risk patients and taking appropriate measures.