Competing risks of mortality with marathons: retrospective analysis

Abstract

Objective: To determine from a societal perspective the risk of sudden cardiac death associated with running in an organised marathon compared with the risk of dying from a motor vehicle crash that might otherwise have taken place if the roads had not been closed.

Design: Population based retrospective analysis with linked ecological comparisons of sudden death.

Setting: Marathons with at least 1000 participants that had two decades of history and were on public roads in the United States, 1975-2004.

Main outcome measures: Sudden death attributed to cardiac causes or to motor vehicle trauma.

Results: The marathons provided results for 3,292,268 runners on 750 separate days encompassing about 14 million hours of exercise. There were 26 sudden cardiac deaths observed, equivalent to a rate of 0.8 per 100,000 participants (95% confidence interval 0.5 to 1.1). Because of road closure, an estimated 46 motor vehicle fatalities were prevented, equivalent to a relative risk reduction of 35% (95% confidence interval 17% to 49%). The net reduction in sudden death during marathons amounted to a ratio of about 1.8 crash deaths saved for each case of sudden cardiac death observed (95% confidence interval: 0.7 to 3.8). The net reduction in total deaths could not be explained by re-routing traffic to other regions or days and was consistent across different parts of the country, decades of the century, seasons of the year, days of the week, degree of competition, and course difficulty.

Conclusion: Organised marathons are not associated with an increase in sudden deaths from a societal perspective, contrary to anecdotal impressions fostered by news media.

Fig 1 Distribution of sudden cardiac deaths according to distance along marathon course when participant collapsed (to nearest mile; 1 mile=1.6 km; total course 26.2 miles, equal to 42 km). Deaths expressed as counts summed over all marathons and years

Fig 2 Comparison of observed crash fatalities on marathon days relative to predicted crash fatalities on control days. Top: counties inside marathon route; bottom: counties outside marathon route and data from corresponding hours of road closures. Each point represents one marathon site summed over all years. Note logarithmic scale and zero values plotted at 1

Fig 3 Ratio of crash fatalities prevented to cardiac deaths observed for average marathon. Values above zero indicate a decrease in crash deaths on marathon days relative to control days. Values over one indicate that number of crash deaths averted on marathon days exceeds number of cardiac deaths on marathon days. Full analysis appears at top based on all marathons and all times. 95% confidence interval calculated from bootstrap techniques. Weekday, winning time, number of participants, and prize money defined by most recent year