What are the health risks of long-distance running?

The unfortunate death of a male participant in a half-marathon race in Dublin at the weekend has put the spotlight on the health risks of long-distance running.

Race fatalities are rare. Since 1981, some 11 participants have died while participating in the London marathon. A 30-year-old woman who died in 2012 was the first female to die during the race. Some seven of the 11 deaths were linked to some form of pre-existing heart disease. One man died from the effects of drinking too much water, while two others died from brain haemorrhage.

A large US study of sudden cardiac death in marathon and half-marathon participants found an overall rate of 0.5 deaths per 100,000 participants.

There is a difference in the type of cardiac disease found in younger and older victims.

Athletes under 35 who die suddenly are often found to have a rare condition called hypertrophic cardiomyopathy (HOCM), in which the heart muscles are enlarged and the structure of the heart disordered.

It’s a different story for middle-aged and senior athletes. Post-mortem studies of older sudden cardiac death victims will often show evidence of coronary heart disease – where there is a blockage or blockages in one or more of the coronary arteries.

Not having given rise to any symptoms until the race itself, the normal stress of competing brings on an acute cardiac event, often a fatal arrhythmia called ventricular fibrillation.

According to the half-marathon organisers, Saturday's victim collapsed at around the 11-mile mark, between three-quarter way into the race and its finish. One research paper has linked the likelihood of a cardiac event to the distance run, with most occurring around the three-quarter mark.

Damaging the heart
Could long-distance running actually damage the heart? In one small Australian study, scientists studied the athletes a fortnight before their races, immediately after their races and then about a week later.

Immediately after the race, the athletes’ hearts had changed shape. The right ventricle – one of the four chambers in the heart involved in pumping blood around the body – appeared dilated and didn’t work as well as it had in the weeks leading up to the race.

In addition, levels of a chemical called BNP, made by the heart in response to excessive stretching, increased. But this was a small study, the findings from which would need to be replicated in larger and longer studies.

Italian doctors have been long-time advocates of cardiac screening in young athletes. They have produced research evidence showing that screening using resting electrocardiograms can prevent deaths in the small number of people with HOCM.

German cardiologist Dr Martin Halle told the 2012 annual congress of the European Society of Cardiology that “marathon running has an increased incidence of sudden cardiac death which is dependent on age, gender and training status”.

For those starting long-distance running, he recommends a clinical examination and a review of the person’s medical and family history.

The risk of a half-marathon is significantly less, he added.

However, as statistics from the most recent research show, the risk of sudden cardiac death is very low. Most health problems that occur during a race or while training are minor injuries such as sprains and muscle strains.

Dehydration is a potential problem especially in races run in hot and humid conditions.

Here are a few general dos and dont's:
For anyone planning to take up long-distance running who has a pre-existing medical condition, a visit to your GP is a must.

If you feel unwell in the days before an event, either do not participate or seek medical advice.

If you have a temperature as a result of a viral or flu-like illness on the day of the marathon, think twice about taking part.

The most important part of safe long-distance running is to follow a sensible and reputable training regime.