The prevalence of hyponatremia increases with ageing in an Italian emergency department population.

The results of our retrospective and descriptive investigation suggest that the prevalence of both moderate and severe hyponatremia observed in an Italian ED is substantially higher than that reported in previous studies and in other countries. Considering that we have chosen the threshold of 136 mmol/L for defining moderate hyponatremia, as suggested by Adrogué and Madias, it is predictable that the frequency of this condition would be substantially reduced using lower cut-offs (i.e., 12.3%, 8.7% and 2.6% using serum sodium values < 135 mmol/L, < 134 mmol/L and < 130 mmol/L, respectively), but still remaining higher than that reported in previous studies. The prevalence of hyponatremia in ED patients was also found to be approximately 5-time higher than that observed in unselected outpatients of the same geographic area. We have also observed that the frequency of both moderate and severe hyponatremia substantially increased with the age of the patients admitted to the ED, with a notable 2.7 higher risk of moderate hyponatremia in patients aged 75 years or older compared to those aged ≤ 25 years.