A review in overhydration underlying Exercise-Associated Hyponatremia

Abstract

Exercise-associated hyponatremia (EAH) is hyponatremia occurring during or up to 24 hours after prolonged physical activity. There is clear evidence that the primary cause of EAH is overconsumption of fluids relative to fluid losses. The electrolyte imbalance, in particular sodium triggered by overhydration is the aetiologic basis behind the illness. If untreated, hyponatremia causes cerebral and pulmonary edema resulting in seizures, coma and on occasion, death. Current understanding of overhydration underlying EAH is discussed. Aetiology, pathology, diagnosis, the role of sodium and preventive measures are key focal points in this review. The body of research spans more than two decades comprising of pioneering and up-to-date studies. Risk factors identified show strong correlation to hyponatremia. It is concluded that the underlying cause is more likely to be a combination of risk factors. Insufficient knowledge in the relationship between contributing risk factors has prompted the proposal of further study. EAH is a complex illness. With the healthconscious population expanding, incidence rates are rising. Educational strategies must be introduced to sport events and to individuals susceptible to EAH, promoting moderate fluid intake “ad libitum”, thus benefiting the general population undertaking prolonged exercise. There is current controversy regarding sodium supplementation to prevent the onset of EAH with the literature supporting positions both for and against this supplement. Excessive sodium supplementation for ultra-endurance athletes may not be viable to counteract low sodium levels. In addition, the role of sodium depletion is not yet fully established, highlighting the necessity for further research in this field.