title: First reported cases of exercise-associated hyponatremia in Asia.
abstract: There are no reported cases of exercise-associated hyponatremia (EAH) in tropical Asia. This study aimed to investigate the incidence of EAH at the on-site medical tent and fluid balance in long distance foot races in a warm and humid environment. Body mass was taken before and after the races (42-km marathon; 84-km ultra-marathon). Blood sodium concentration was measured for symptomatic runners admitted to the medical tent. Mean (SD) dry bulb temperature was 29.0 (0.6)°C, relative humidity 89 (2)% and wind speed 0.3 (0.5) m/s. Three out of the 8 symptomatic runners admitted to the medical tent were diagnosed with hyponatremia, with blood sodium concentrations of 134 mmol/L in a 42-km runner, and 131 and 117 mmol/L in two 84-km runners. In the 42-km race, mean % ΔBM was -1.6 (1.2)%, ranging from -5.7 to 1.4%, and 22 runners (7%) gained weight. In the 84-km race, mean % ΔBM was -2.3 (1.7)%, ranging from -8.0 to 1.4%, and 9 runners (8%) gained weight. In addition to the 3 cases of symptomatic hyponatremia observed, 8% of the 84-km runners and 7% of the 42-km runners gained weight during the race. This indicates the need to disseminate advice for the prevention and treatment of EAH for races held in the tropics.
authors.affiliation: Military Physiology Laboratory, Defence Medical & Environmental Research Institute, DSO National Laboratories, Singapore. lkaiwei@dso.org.sg
authors.forename: J K W
authors.initials: JK
authors.lastname: Lee
authors.forename: A Q X
authors.initials: AQ
authors.lastname: Nio
authors.forename: W H
authors.initials: WH
authors.lastname: Ang
authors.forename: C
authors.initials: C
authors.lastname: Johnson
authors.forename: A R
authors.initials: AR
authors.lastname: Aziz
authors.forename: C L
authors.initials: CL
authors.lastname: Lim
authors.forename: T
authors.initials: T
authors.lastname: Hew-Butler
mesh_terms: D001208:Asia / Q000453:epidemiology; D015444:Exercise; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D010807:Physical Endurance / Q000502:physiology; D012420:Running / Q000502:physiology*; D014329:Tropical Climate