What is the clinical evidence from this study?

Study design: Systematic Review. Population: Sudden cardiac death. Intervention: Marathon running. Primary outcome: Incidence of sudden cardiac death (SCD) (0.6 to 1.9 per 100,000).

December 21, 2015Open Access

Sudden cardiac death in marathons: a systematic review

OWOliver WaiteYork St John University ASAndy SmithYork St John University LMLuke MadgeYork St John University

Key Result

The incidence of sudden cardiac death during or immediately after marathons is very low, ranging from 0.6 to 1.9 per 100,000 runners.

Study Design

Type

Systematic Review

Structured PICO

Population

A systematic review of 7 cohort studies evaluating the incidence of sudden cardiac death among hundreds of thousands of marathon runners in the US and UK.

Exposure

Marathon running

Outcome

Incidence of sudden cardiac death (SCD) during or immediately after the marathonhard clinical

Sudden cardiac death during marathons is a very rare event, with an estimated incidence ranging from 0.6 to 1.9 per 100,000 runners, though methodological inconsistencies limit precise risk quantification.

Main Result

Effect estimate: 0.6 to 1.9 per 100,000

Limitations

Methodological concerns over collating reports of SCD in marathons, leading to potential overlap between studies.
Inconsistent definitions of time of death in relation to the marathon.
Use of race registrants rather than actual runners in sample size estimates.
Limited detail on runners' exercise and medical history.
Failure of included studies to identify and control for important confounding factors such as diet, age, and gender.

Abstract

The aim of this systematic review is to summarise the results of cohort studies that examined the incidence of SCD in marathons and to assess the quality of the methods used. A search of the PROSPERO international database revealed no prospective or published systematic reviews investigating SCD in marathons. The review was conducted using studies that reported and characterised the incidence of SCD in people participating in marathons. Studies were identified via electronic database searches (Medline, CINAHL, SPORTDiscus and Google Scholar) from January 1, 1966 to October 1, 2014 and through manual literature searches. 7 studies met the inclusion criteria and were included in this review. 6 of the studies were conducted in the USA and 1 in the UK. These studies covered a 34-year period involving between 215,413 and 3,949,000 runners. The SCD of between 4 and 28 people are recorded in the papers and the reported estimates of the incidence of SCD in marathons ranged widely from 0.6 to 1.9 per 100,000 runners. The proportion of those suffering SCD who were male ranged from 57.1% to 100% and the mean age reported in the papers, ranged from 37 to 48. This review raises 4 methodological concerns over i) collating reports of SCD in marathons; ii) time of death in relation to the marathon; iii) the use of registrants rather than runners in the estimates of sample size and iv) limited detail on runners exercise history. These four concerns all threaten the reliability and interpretation of any estimate of SCD incidence rates in marathons. This review recommends that the methods used to collect data on SCD in marathons be improved and that a central reporting system be established.

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