Marathons and Cardiac Arrest: Causes, Warning Signs and Precautions for Hyderabad Runners

Hyderabad's running scene has grown quickly, with first-time half-marathoners and weekend 10K runners now a common sight on cooler mornings. News of a runner collapsing after a race, including here in the city, understandably leaves people asking whether running is safe for the heart. The honest answer is that cardiac arrest during a marathon is rare, but it is not random: there are known causes, known warning signs, and precautions that genuinely reduce the risk.

Cardiac arrest is not the same as a heart attack

A heart attack happens when a blocked artery cuts blood supply to part of the heart muscle. Cardiac arrest is an electrical failure: the heart suddenly stops pumping effectively, and the person collapses and stops breathing normally. A heart attack can trigger a cardiac arrest, but cardiac arrest can also come from rhythm disorders or structural heart conditions with no blockage at all. The difference matters because cardiac arrest is survivable mainly through the first few minutes of CPR and defibrillation.

How common is it, really?

A recent review of marathon-associated sudden cardiac death pooled figures from several race registries. Across 8 registries covering more than 16 million runners, the incidence of cardiac arrest was 0.82 per 100,000 runners, with a mortality of 0.39 per 100,000.

Source: review of marathon-associated sudden cardiac death (8 race registries, 16,223,866 runners; US data 2000–2023). Event definitions differ between datasets, so figures are not strictly interchangeable.

That last figure is the encouraging one: in US race data, the share of cardiac arrests that proved fatal fell from 71% to 34% as race medical support improved.

What the Indian numbers show

Those race figures come mostly from Western and Japanese registries. India has no comparable registry of race-related cardiac arrests, but national data on heart disease explain why the issue deserves attention here.

Sources: Registrar General of India, Sample Registration Survey, Report on Causes of Death 2021–2023; WHO-based estimates cited in a 2026 review of Indian cardiovascular mortality. Different sources use different definitions, so the shares are not identical.

In other words, heart disease in India tends to appear earlier, in the same decades when many people take up marathon training. Race-day reports show what is at stake. At the 2024 Mumbai Marathon, two runners, aged 75 and 46, died during the full marathon and 22 participants were hospitalised, for dehydration and other reasons. Without participant numbers, no rate can be calculated from such reports, but they are a reminder that the pre-race checks described below are worth taking seriously.

What causes it, and why age changes the answer

The causes differ sharply by age, which is why one rule does not fit every runner.

Much of the data on younger athletes comes from non-marathon sports cohorts, so it is indicative rather than marathon-specific.

Who is at higher risk, and when do events happen?

Men, older runners and those running a full marathon rather than a half carry higher risk. Most events occur in the last part of the race or just after finishing, and the runners affected were not slower or faster than the typical finisher, so this is not simply a matter of pushing too hard. Japanese data show the rate rising with age, from 0.9 per 100,000 in runners in their 40s to 2.6 in their 50s and 5.5 in those aged 60 and above.

There is a local angle too. A study of IT-sector employees in Hyderabad found 76.5% with high LDL cholesterol, 70.7% classed as obese, 34.2% with metabolic syndrome and 71.9% sitting for more than 8 hours a day (n=345). Many of the city's newer runners fit that picture: desk-bound all week, then asking the heart to do something demanding on race morning. Silent risk factors are often already in place.

Warning signs not to run through

Cardiac arrest sometimes arrives without warning, but many runners notice something first. These are worth stopping for and getting checked rather than pushing on:

Symptoms during exercise deserve a medical check even if they settle once you stop.

Precautions before you register

Screening guidance differs by country. European guidance calls for a resting ECG for competitive athletes, while US guidance relies on history and examination first. For recreational runners over 35, reviewers suggest a validated self-screening questionnaire, followed by a clinical evaluation if any answer is positive. If you have known coronary artery disease, training and race plans should be individualised after your doctor assesses how much of your heart is at risk.

Beyond screening, a few habits lower risk: build mileage gradually instead of jumping from the sofa to a half marathon; avoid hard training while unwell, and return slowly after an infection, since early return to intense exercise after myocarditis raises risk; and keep blood pressure, sugar and cholesterol under treatment if they are high.

Race day: what to do, and what organisers should have

Do not ignore symptoms because the finish line is close, since many events happen in the final stretch or just after crossing it. Keep moving gently after finishing rather than stopping abruptly, and tell a medic if anything feels wrong.

Race medical support should aim for CPR within 1 minute and defibrillation within 3 minutes. In Japanese cases where those timings were met, 95.5% achieved complete neurological recovery. Check that a race has marked AED points and medical teams on the route before you enter, and learn hands-only CPR: if someone collapses and is not breathing normally, call 112 or 108, start chest compressions and send someone for an AED.

Frequently asked questions