Comment on: Hyponatremia–associated hospital visits are not reduced by early electrolyte testing in older adults starting antidepressants

Abstract

We read the article by Lane et al.¹ with great interest. They demonstrated that the early testing rate of serum sodium levels and the need for hospitalization due to hyponatremia were lower than expected in the study population that started on antidepressant therapy. In support of these findings, it was speculated by the authors that early sodium testing in all patients with antidepressant treatment may not be clinically beneficial. Although the study has a suitable methodology and an excellent presentation, further prospectively designed studies are warranted to test these hypotheses investigated in the recent study before changing routine clinical practice. We know that hyponatremia is a significant cause of morbidity and even mortality in this older patient population.² Current guidelines emphasize the importance of close follow-up of the patients by measuring their serum sodium levels, especially in older people who have newly started antidepressants because antidepressant-associated hyponatremia is usually observed within the first weeks after initiation of the treatment.³

Moreover, it has been emphasized that sodium monitoring should not be forgotten after the initiation of antidepressant treatments, especially in older individuals who are concomitantly using drugs such as diuretics that may decrease serum sodium levels.⁴ Supportingly, the recent study observed that the most common underlying comorbidities in patients requiring hospitalization due to hyponatremia were heart failure and urinary tract infection. Therefore, sodium monitoring should be kept in mind when evaluating patients who have additional conditions that may increase the risk of hyponatremia and started antidepressant therapy.

Another critical point taken from the recent study is the exclusion from the study of about four thousand patients who died during the follow-up period after antidepressant treatment initiation. If most of these excluded patients were in the group without monitoring serum sodium levels, this may cause a selection bias in the study. Therefore, if the data of these deceased patients can be accessed in detail and included in the analyses, it may strengthen the study's results. Alternatively, there are conflicting data in the literature regarding the cutoff point of serum sodium levels in patients using antidepressants to predict symptomatic hyponatremia.⁵ The recent study reported that the median serum sodium value of patients requiring hospitalization was 132 mmol/L. However, we could not find any clear information about whether these hospital admissions were due to symptomatic hyponatremia or not. Therefore, some reasons for admission or symptoms in the study population may have derived from another clinical condition other than hyponatremia. A detailed examination of the symptoms in the hospitalized group may strengthen the study's findings; however, due to retrospective design, the data showing the mentioned points may not be available, which may be a limitation of the study.

Another point is that approximately 25% of the hospitalized group stayed for about 12 days. Information on the final hospital status of these patients or the hospital mortality rates in this group may enrich the study's findings. Moreover, it would be better if the length of hospital stay and other hospital clinical outcomes were compared with patients who did not undergo early sodium monitoring but were hospitalized. If this information is unavailable, it can be considered another study limitation.

IA and MCK wrote the letter, and all coauthors have read and approved the final version of the manuscript.

The authors declare no conflicts of interest.

None.

No specific funding was received for this work.