K. Johnson1, C. Connolly1, S. Cho1, T. Miller2, R. Laird3, W. D. Hiller1,

1Washington State University, Pullman, WA

2Virginia Tech Carilion School of Medicine, Roanoke, VA

3Kona Community Hospital, Kona, HI

Exercise-associated hyponatremia (EAH) is an electrolyte imbalance that most commonly occurs during ultra-endurance athletic events and may result in serious complications. Severe cases of EAH are more commonly reported in females but there is a lack of high-quality observational studies comparing the risks by sex. PURPOSE: To compare the clinical presentation (CP) of EAH between male and female triathletes over the course of three decades of ultra-endurance competitions. METHODS: Medical records with [Na+] values (n=3,138) from a single Ironman-distance triathlon over the timeframe of 1989-2019 were reviewed for both male (n=2,253) and female (n=885) competitors. Loglinear analyses were run to determine interactions among sex, sodium status, and various CPs (complaints, diagnoses, vitals, lab values, and weight change). Effects were then explored by calculating percentage of triathletes with those CPs as well as odds ratios with 95% confidence intervals, specifically comparing male and female triathletes with EAH, to those without. Lastly, non-binary CPs were compared using Independent samples t-tests. RESULTS: When comparing triathletes with EAH to those without, males were more likely to present with altered mental status (OR 1.61; 95% CI = 1.22-2.33) and diarrhea (OR 1.45; 95% CI = 1.00-2.11), while females were not; Females were more likely to present with vomiting (OR 1.63; 95% CI = 1.21-2.19), while males were not; And males were less likely to present with abdominal pain (OR 0.70; 95% CI = 0.51-0.94), hypotension (OR 0.52; 95% CI = 0.36-0.76), tachycardia (OR 0.56; 95% CI = 0.38-0.83), and hyperkalemia (OR 0.71; 95% CI = 0.51-0.99), while females were not. Overall, males lost significantly more weight (Mean = -5.8 lbs.; SD = 6.3 lbs.) than females (Mean= -1.1 lbs.; SD = 5.2 lbs.) (t(777) = -11.06, p<0.001). EAH males (OR 5.85; 95% CI = 3.29-10.38) and EAH females (OR 3.32; 95% CI = 1.99-5.55) were more likely to gain weight than non-EAH males and females. CONCLUSIONS: Altered mental status, diarrhea, vomiting, abdominal pain, hypotension, tachycardia, and hyperkalemia appear to present differently between sexes. Further understanding of how EAH presents in males and females helps both athletes and medical professionals identify it early and prevent life threatening complications.

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