Antipsychotic use is a risk factor for hyponatremia in patients with schizophrenia: a 15-year follow-up study

Hyponatremia affects 10% of patients with chronic schizophrenia and can lead to severe consequences. However, the role of antipsychotics and other risk factors in hyponatremia occurrence has remained inconsistent.

This study examined the association between antipsychotic use and hyponatremia occurrence in patients with schizophrenia.

We utilized the National Health Insurance Research Database to follow 2051 patients with schizophrenia from 1998 to 2013. Among them, 137 (6.7%) developed hyponatremia. Sociodemographic characteristics, physical comorbidities, and psychiatric treatment experiences were compared between those who had hyponatremia and those who did not. A Cox proportional hazards model was used to examine the hazard ratios (HRs) of these characteristics.

In patients with hyponatremia, the mean age at first hyponatremia occurrence was 54.7 ± 13.9 years, an average of 9.5 ± 4.0 years after schizophrenia diagnosis, and 32.9% of them were off antipsychotics before hyponatremia occurrences. Age at schizophrenia diagnosis (HR = 1.1), low-income household (HR = 2.4), comorbidities (HR = 1.2), and psychiatric admissions (HR = 1.04) were associated with the risks of hyponatremia. Compared with no antipsychotic use, atypical (HR = 2.1) and typical antipsychotics (HR = 3.1) were associated with an elevated risk of hyponatremia, after adjustment for age, sex, and physical comorbidities. Carbamazepine use (HR = 2.9) was also a significant risk factor for hyponatremia (p < 0.05).

Antipsychotic use in patients with schizophrenia with polypharmacy should be monitored for hyponatremia occurrences. Clinicians should pay attention to the impact of poor living conditions on hyponatremia occurrence.