The 26 marathons over the 30 years provided results for 2250 separate days of observation (750 marathon days and 1500 control days). Collectively, this amounted to 3
268 participants each running 42 km (26.2 miles). Over the 30 years there were 26 sudden cardiac deaths. Fifteen marathons had no deaths, six had one, and five had more than one (Boston, New York, Chicago, Honolulu, Washington Marine Corps). One marathon had more than one death in a single year (New York with two deaths in 1994). No major trend in cardiac deaths was observed over the years.
The typical participant with sudden cardiac death was a middle aged adult man (average age 41 years, 81% men). Five deaths occurred in individuals who had previously completed a marathon. Autopsy results were available for 24, the most common finding being coronary atherosclerosis (n=21). Other contributing factors in scattered cases included electrolyte abnormalities (n=4), coronary anomalies (n=2), and heat stroke (n=1). The most common course location of cardiac death was at or within 1.6 km (1 mile) of the finish line (fig 1).
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 (more ...)
The overall risk of sudden cardiac death was equal to 0.8 per 100
000 participants (95% confidence interval 0.5 to 1.1). This was equivalent to about three deaths per 42 km of roadway per 1000 hours. No individual marathon course had an observed risk of sudden cardiac death that was significantly higher or lower than this baseline risk. The risk of sudden cardiac death was collectively distributed over about 86 million total miles of running by participants and mathematically equal to about two deaths per million hours of exercise.
Over the 30 years a total of 12
364 motor vehicle fatalities occurred on the 750 marathon days and 1500 control days in the corresponding states. A minority (n=930) were in counties inside the course whereas most (n=11
434) were in counties outside the course. The typical person who died in a fatal crash was a middle aged adult man (mean age 38 years, 78% men). About 56% were drivers, 25% were passengers, and 19% were pedestrians or other vulnerable road users. Marathon courses varied markedly around the prevailing average with no systematic week to week trend in crash deaths.
A total of 85 individuals died in fatal crashes on the marathon days in counties inside the course during hours when roads were closed. In contrast, 262 individuals died in fatal crashes on the control days in the corresponding counties and hours. Given that each marathon was paired with two control days, the discrepancy between observed and expected crash deaths on marathon days corresponded to a 35% relative decrease in risk (17% to 49%). This discrepancy was equal to an absolute decrease of 46 total crash deaths over the study (P<0.001).
We observed no major spillover in crash deaths to surrounding regions attributable to re-routing of traffic. Analysis of counties outside the course that compared observed with expected crash deaths during hours of road closure showed no countervailing increase in fatal crashes (relative decrease 0%, −6% to 7%). This discrepancy was equal to an absolute decrease of five deaths (P>0.20). Inspection of scatter plots showed no major departures from the general pattern of decreased crash deaths inside the marathon course and no increase in crash deaths outside the marathon course (fig 2).
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 (more ...)
Secondary analyses also showed no spillover in crash deaths to days surrounding the marathon for the counties involved in the road closures. Focusing on the three days before the marathon during the corresponding hours, we observed no significant increase in risk (relative increase in deaths 3%, absolute increase in deaths 9, P>0.20). Focusing on the three days after the marathon during the corresponding hours, we observed no significant increase in risk (relative decrease in deaths 4%, absolute decrease in deaths 11, P>0.20).
The ratio of crash deaths prevented was about 1.8 for each case of sudden cardiac death attributed to the marathon (95% confidence interval 0.7 to 3.8). The reduced risk of sudden death was consistent across different regions of the country, decades of the century, seasons of the year, days of the week, degree of competition (as measured by prize money), and course difficulty (as measured by winning race time). Each subgroup showed a protective association, though confidence intervals were wide in all cases (fig 3).
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 (more ...)