Hyponatremia is the most common electrolyte disorder in outpatients and hospitalized patients. The prevalence of hospital-associated hyponatremia is estimated to be up to 40%. Especially mild to moderate hyponatremia (125-136 mmo/l) without apparent symptoms has seldomly been accurately assessed but rather seen as clinically irrelevant. Cognitive limitations, unstable gait and motoric disorders as well as depressive conditions were described in smaller studies and single case reports.