Hyponatremia among Runners in the Boston Marathon

Department of Medicine, Children's Hospital, Boston, MA 02115, USA.
New England Journal of Medicine (Impact Factor: 55.87). 04/2005; 352(15):1550-6. DOI: 10.1056/NEJMoa043901
Source: PubMed


Hyponatremia has emerged as an important cause of race-related death and life-threatening illness among marathon runners. We studied a cohort of marathon runners to estimate the incidence of hyponatremia and to identify the principal risk factors.
Participants in the 2002 Boston Marathon were recruited one or two days before the race. Subjects completed a survey describing demographic information and training history. After the race, runners provided a blood sample and completed a questionnaire detailing their fluid consumption and urine output during the race. Prerace and postrace weights were recorded. Multivariate regression analyses were performed to identify risk factors associated with hyponatremia.
Of 766 runners enrolled, 488 runners (64 percent) provided a usable blood sample at the finish line. Thirteen percent had hyponatremia (a serum sodium concentration of 135 mmol per liter or less); 0.6 percent had critical hyponatremia (120 mmol per liter or less). On univariate analyses, hyponatremia was associated with substantial weight gain, consumption of more than 3 liters of fluids during the race, consumption of fluids every mile, a racing time of >4:00 hours, female sex, and low body-mass index. On multivariate analysis, hyponatremia was associated with weight gain (odds ratio, 4.2; 95 percent confidence interval, 2.2 to 8.2), a racing time of >4:00 hours (odds ratio for the comparison with a time of <3:30 hours, 7.4; 95 percent confidence interval, 2.9 to 23.1), and body-mass-index extremes.
Hyponatremia occurs in a substantial fraction of nonelite marathon runners and can be severe. Considerable weight gain while running, a long racing time, and body-mass-index extremes were associated with hyponatremia, whereas female sex, composition of fluids ingested, and use of nonsteroidal antiinflammatory drugs were not.

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Available from: David P Olson, Feb 11, 2015
    • "Many factors contribute to athletic success in endurance events, including aerobic capacity, cardiovascular efficiency, and body fluid status. Participation in physical exercise, especially prolonged exercise, incurs stress on numerous physiological systems, and appropriate compensatory responses are essential for maximal endurance performance (Almond et al., 2005; Cheuvront et al., 2005; Coyle, 2004; Davis et al., 2001; Fallo, 1993; Horowitz and Klein, 2002; Staessen et al., 1987). Central and peripheral control of body fluid homeostasis are influenced by sex hormones, especially oestrogen, which modulates sensitivity to osmotic stimuli, alters release of regulatory hormones such as angiotensin II, aldosterone, and vasopressin, and modifies cardiovascular responses (Barrron et al., 1986; Crofton and Share, 1990; Jones and Curtis, 2009; Jones et al., 2012; Krause et al., 2003, 2007; Kuroski de Bold, 1999; Pamidimukkala and Hay, 2003; Shapiro et al., 2000; Stachenfeld, 2008; Stachenfeld and Keefe, 2002; Stachenfeld et al., 1998, 1999; Xue et al., 2009). "
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    ABSTRACT: Athletic performance in endurance exercise is determined by an interplay among many physiological factors. Body fluid regulation, influenced by both hormonal and osmotic stimuli, is particularly important for maximising performance in endurance sports, as dehydration markedly decreases endurance. Oestrogen has a broad range of effects on the regulation of body fluid balance, as well as on aerobic capacity, metabolism, and other factors that impact endurance exercise performance, yet the role of oestrogen in endurance exercise performance has not been thoroughly examined. This review discusses the effects of oestrogen on compensatory hormonal and behavioural responses to dehydration, such as renin-angiotensin-aldosterone system activation and thirst, that restore body fluid balance and thereby affect exercise performance. Oestrogen-mediated effects and their potential consequences for endurance performance are also evaluated in the context of thermoregulation and aerobic capacity, as well as substrate utilisation during exercise. In addressing the role of oestrogen in endurance exercise, this review will examine human and animal models of endurance exercise and discuss similarities, differences, and limitations. Our aim is to integrate research from neuroscience, physiology, and exercise science to advance understanding of how oestrogen may impact exercise. Such understanding will have particularly important implications for female endurance athletes experiencing the hormonal fluctuations that occur during the reproductive cycle.
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    • "Finishing a marathon or other endurance event typically results in approximately 2–3 % loss in TBW concomitant with increases in plasma sodium concentration of approximately 5–7 mEq/L. In EAH, some athletes (1–13 %) reduce sodium concentration by 5 mEq/L or greater relative to pre-race values at the end of endurance exercise [44, 45], usually the result of excess hypotonic fluid ingestion accompanied by significant water retention. Mechanisms contributing to EAH have proved difficult to examine because the studies in which athletes have EAH following racing are retrospective; that is, athletes are examined and grouped after they have become hyponatremic during a race but are not grouped before the race with the purpose of measuring drinking behavior or other variables associated with EAH in the field. "
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    ABSTRACT: Changes in skin blood and sweating are the primary mechanisms for heat loss in humans. A hot, humid environment concomitant with dehydration limits the ability to increase skin blood flow for the purpose of transferring heat from the body core to skin surface and evaporate sweat to maintain core temperature within safe limits during exercise. Adequate hydration improves thermoregulation by maintaining blood volume to support skin blood flow and sweating. Humans rely on fluid intake to maintain total body water and blood volume, and have developed complex mechanisms to sense changes in the amount and composition of fluid in the body. This paper addresses the interrelationship of research in the laboratory and the field to assess hydration status involved in body water and temperature regulation during exercise. In the controlled setting of a research laboratory, investigators are able to investigate the contributions of volume and tonicity of fluid in the plasma to body water and temperature regulation during exercise and recovery. For example, laboratory studies have shown that tonicity in a rehydration beverage maintains the thirst mechanism (and stimulates drinking), and contributes to the ongoing stimulation of renal fluid retention hormones, ultimately leading to a more complete rehydration. Research in the field cannot control the environment precisely, but these studies provide a natural, 'real-life' setting to study fluid and temperature regulation during exercise. The conditions encountered in the field are closest to the environment during competition, and data collected in the field can have an immediate impact on performance and safety during exercise. There is an important synergy between these two methods of collecting data that support performance and protect athletes from harm during training and improve performance during competition.
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    • "Even a relationship between heat periods and mortality in the overall population has been shown previously and the high number of deaths during the heat period in Europe in 2003 especially among the elderly found attention by the popular media [8], [9]. Given the pathophysiology of disorders of serum sodium, but also of serum potassium it is well imaginable that during prolonged periods of extreme temperatures with increased sweating an increase in the prevalence of electrolyte disorders due to dehydration or excess intake of free water, as described in endurance runners can be observed [10], [11]. However, so far no study has investigated the impact of temperature extremes on the prevalence of electrolyte disorders. "
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    ABSTRACT: Heat periods during recent years were associated with excess hospitalization and mortality rates, especially in the elderly. We intended to study whether prolonged warmth/heat periods are associated with an increased prevalence of disorders of serum sodium and potassium and an increased hospital mortality. In this cross-sectional analysis all patients admitted to the Department of Emergency Medicine of a large tertiary care facility between January 2009 and December 2010 with measurements of serum sodium were included. Demographic data along with detailed data on diuretic medication, length of hospital stay and hospital mortality were obtained for all patients. Data on daily temperatures (maximum, mean, minimum) and humidity were retrieved by Meteo Swiss. A total of 22.239 patients were included in the study. 5 periods with a temperature exceeding 25°C for 3 to 5 days were noticed and 2 periods with temperatures exceeding 25°C for more than 5 days were noted. Additionally, 2 periods with 3 to 5 days with daily temperatures exceeding 30°C were noted during the study period. We found a significantly increased prevalence of hyponatremia during heat periods. However, in the Cox regression analysis, prolonged heat was not associated with the prevalence of disorders of serum sodium or potassium. Admission during a heat period was an independent predictor for hospital mortality. Although we found an increased prevalence of hyponatremia during heat periods, no convincing connection could be found for hypernatremia or disorders of serum potassium.
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