title: Incidence of Exercise-Associated Hyponatremia and Its Association With Nonosmotic Stimuli of Arginine Vasopressin in the GNW100s Ultra-endurance Marathon.
abstract: OBJECTIVE
  (1) To examine the incidence of exercise-associated hyponatremia (EAH) during and after an ultramarathon and (2) to evaluate hypothesized nonosmotic stimuli [interleukin-6 (IL-6), hypoglycemia, ambient temperature] with arginine vasopressin (AVP) concentrations in hyponatremic versus normonatremic runners.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  The Great North Walk 100s ultramarathons.
  
  
  METHODS
  Fifteen runners participated in either 103.7- or 173.7-km ultramarathons.
  
  
  METHODS
  Serum sodium concentration ([Na]) and AVP concentration. Secondary outcome measures included IL-6, blood glucose, ambient temperature, weight change, fluid consumption, and use of nonsteroidal anti-inflammatory drugs (NSAIDs).
  
  
  RESULTS
  Postrace EAH incidence was 4 of 15 runners, whereas EAH incidence at any point during the race was in 10 of 15 runners. A significant positive correlation was noted between AVP and IL-6 (r = 0.31, P < 0.05) but not between AVP and blood glucose (r = 0.09, nonsignificant) or ambient temperature (r = -0.12, NS). Subgroup analysis revealed that the correlation between AVP and IL-6 was significant in hyponatremic (r = 0.37, P < 0.05) but not normonatremic runners (r = 0.31, NS). Hyponatremic runners lost less weight than normonatremic runners (2.5 vs. 3.7 kg, P < 0.05, respectively) despite similar fluid consumption. Seven of 10 hyponatremic runners consumed NSAIDs versus 0 of 5 normonatremic runners.
  
  
  CONCLUSIONS
  Exercise-associated hyponatremia incidence mid-race is higher than postrace, suggesting that 40% of runners are able to self-correct low serum [Na] status during an ultramarathon. Interleukin-6 seems to be the main nonosmotic stimulus associated with AVP in hyponatremic runners. Nonsteroidal anti-inflammatory ingestion is more common in hyponatremic versus normonatremic runners.
  
  
  CONCLUSIONS
  Exercise-associated hyponatremia associated with nonosmotic AVP secretion may be more common during ultramarathon races without discriminatory clinical symptomatology.
authors.affiliation: *Newcastle Sports Medicine, Charlestown, Australia; and †School of Health Sciences, Oakland University, Rochester, Michigan.
authors.forename: Ross S
authors.initials: RS
authors.lastname: Cairns
authors.forename: Tamara
authors.initials: T
authors.lastname: Hew-Butler
mesh_terms: D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D001127:Arginine Vasopressin / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight; D015331:Cohort Studies; D004327:Drinking Behavior; D006801:Humans; D007003:Hypoglycemia / Q000097:blood / Q000453:epidemiology*; D007010:Hyponatremia / Q000097:blood / Q000453:epidemiology*; D015994:Incidence; D015850:Interleukin-6 / Q000097:blood*; D016014:Linear Models; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012420:Running; D012964:Sodium / Q000097:blood*; D013696:Temperature
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D001786:Blood Glucose; C508600:IL6 protein, human; D015850:Interleukin-6; D001127:Arginine Vasopressin; D012964:Sodium