BOSTON — The death of a 28-year-old runner in this year's Boston Marathon was caused by a critical sodium imbalance brought on in part by drinking too much fluid, according to the state medical examiner.
Cynthia Lucero died from a condition known as hyponatremic encephalopathy, which happens when the brain becomes swollen because of a critical imbalance of sodium, the medical examiner's office said Monday.
Runners have long known the importance of replenishing fluids, but if they drink too much fluid, they can dangerously dilute their blood sodium levels.
Friends said Lucero drank large amounts of Gatorade and looked well for most of the April 16 race. She later began to falter, then collapsed after telling a friend that she felt dehydrated and rubber-legged. She died later at a hospital.
Dr. Arthur J. Siegel, director of internal medicine at McLean Hospital, who has studied the death, told The Boston Globe that the syndrome that killed her is more complicated than simply taking in too much fluid.
He and other researchers theorize that athletes in extreme sporting competitions often deplete the fuel that powers the body's cells, releasing a hormone that leads to an imbalance in blood sodium levels.
Lucero's death showed that even runners who drink sodium-laden sports drinks such as Gatorade remain at risk. Siegel and others are looking at measures to help monitor runners' health include weighing them before and after races.
She was the second runner to die in the marathon's 106-year history. In 1996, a Swedish runner died of a heart attack at the finish line.