Lower serum sodium level predicts poor clinical outcomes in patients with insomnia

Abstract

Background The association of lower serum sodium levels with clinical outcomes in insomnia patients remains unclear. We explored whether lower serum sodium is associated with poor clinical outcomes in patients with insomnia. Methods We retrospectively enrolled patients with a diagnosis of insomnia from January 2011 to December 2012. We divided participants into three groups according to initial serum sodium level: tertile 1 (< 138 mmol/L), tertile 2 (138.0–140.9 mmol/L), and tertile 3 (≥ 141.0 mmol/L). To calculate the relative risk of death, hazard ratios (HRs) and 95% confidence intervals (CIs) were obtained using Cox proportional hazard models. Result A total of 412 patients with insomnia were included, of whom 13.6% (n = 56) had hyponatremia. Patients with lower serum sodium concentrations were older and had lower hemoglobin, calcium, phosphorus, and albumin levels. At the median follow-up of 49.4 months, 44 patients had died and 62 experienced acute kidney injury (AKI). Kaplan-Meier analysis showed significantly higher mortality in patients in the lowest tertile for serum sodium. Lowest tertile of serum sodium, and AKI were associated with all-cause mortality. However, lowest tertile of serum sodium was not significantly associated with AKI. Conclusions The lowest tertile of serum sodium was associated with a higher mortality rate in insomnia patients. Our results suggest serum sodium level could be used one of the prognostic factor in insomniacs and physicians should be careful to take care of them when they present lower sodium level.