Dose of Jogging and Long-Term Mortality The Copenhagen City Heart Study

Schnohr P, O’Keefe JH, Marott JL et al.,
J Am Coll Cardiol. 2015;65(5):411-419. doi:10.1016/j.jacc.2014.11.023

Background

Data strongly support an inverse association between regular exercise and mortality, and guidelines generally recommend >30 min of moderate-intensity physical activity, preferably on a daily basis. No recommendations have on an upper threshold for physical activity.
Several reports have been published on sudden deaths that occurred during jogging [1-6]. The Copenhagen City Heart Study [7,8] previously published that the relative intensity of walking and cycling was most important in relation to all-cause death and coronary heart disease (CHD) mortality, more so than duration of exercise.
In a random sample of 1878 joggers who were followed for up to 35 years, and who were compared with 16827 nonjoggers, different longevity benefits were seen depending on the intensity and frequency of exercise. Lowest mortality was seen with up to 2.5 hours of jogging per week at a slow or average pace and a frequency of <3 times per week [9].This prospective study further explores the observed U-shaped relation between mortality and dose of jogging (based on pace, quantity and frequency).

Main results

• In up to 12 years of follow-up, 28 deaths were registered among 1098 joggers and 128 deaths among 413 sedentary nonjoggers. The average number of years of jogging was 10.1.
• Jogging from 1-2.4 hours per week was associated with the lowest mortality (multivariable HR: 0.29, 95%CI: 0.11-0.80).
• The subgroup with higher jogging dose (2.5-4 h/wk) did not differ significantly from the sedentary group with respect to mortality (HR: 0.65, 95%CI: 0.20-2.07).
• The lowest risk of mortality was seen in those who jogged 2-3 times per week (HR: 0.32, 95%CI: 0.15-0.69), or <1 time per week (HR: 0.29, 95%CI: 0.12-0.72). Risk estimates for those jogging >3 times per week did not differ statistically from those for the sedentary group.
• Slow (HR: 0.51, 95%CI: 0.24-1.10) and moderate jogging pace (HR: 0.38, 95%CI: 0.22-0.66) were associated with lower mortality. Risk of fast-paced joggers did not differ from that in sedentary nonjoggers (HR: 0.94, 95%CI: 0.40-2.18).
• When joggers were divided into 3 groups (light, moderate and strenuous) and compared with the sedentary nonjoggers, light (HR: 0.22, 95%CI: 0.10-0.47) and moderate (HR: 0.66, 95%CI: 0.32-1.38) had a lower risk of all-cause mortality. Strenuous joggers showed a higher risk (HR: 1.97, 95%CI: 0.48-8.14).

Conclusion

These findings show a U-shaped relationship between jogging and mortality, with the lowest mortality seen among light joggers (1-2.4 hours per week, no more than 3 days per week, at a slow or average pace), with respect to pace, quantity and frequency of jogging. Mortality rate in strenuous joggers did not significantly differ from that of sedentary nonjoggers. These findings suggests that there may be an upper limit for exercise dosing that is optimal for health benefits, as some of the longevity benefits conferred by lower dose jogging appear to be lost with higher doses.

Editorial comment [11]

“Considering the current consensus of a linear dose-response relationship between total physical activity (PA) and health, indicating “the more the PA, the better for health and longevity,” these findings are intriguing. The good news is that the mortality benefits of light jogging will encourage more people to jog for health benefits as a “practical, achievable, and sustainable” goal, as
the authors have stated.”
A few study limitations need to be considered. For instance, the sedentary nonjoggers were more obese, older and had a much higher prevalence of hypertension and diabetes mellitus than did the joggers in this study. Statistical analyses probably cannot completely eliminate the confounding bias of these differences, potentially leading to overestimation of the mortality benefit of jogging.
Also, sample sizes were limited in the highest jogging categories, which could mean that a mortality benefit would have been seen if the groups were larger.
This study only focused on the effect of jogging of all-cause mortality. Potential adverse effects of excessive aerobic exercise specifically on cardiovascular diseases and mortality has been reported, while other studies have also published opposite results. In order to prevent unnecessarily frightening people who wish to participate in more strenuous exercise, further studies should better evaluate this controversial issue.
“The general consensus of the data certainly suggests that “more is not better!” regarding running and mortality. However, we still need more data to truly determine “is more actually worse?” regarding exercise dose and prognosis.”

Find this article online at JACC

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