Author + information
- Martijn F.H. Maessen, MSc,
- Maria T.E. Hopman, MD, PhD,
- André L.M. Verbeek, MD, PhD and
- Thijs M.H. Eijsvogels, PhD∗ ()
- ↵∗Radboud University Medical Center, Department of Physiology (392), P.O. Box 9101, 6500 HB Nijmegen, the Netherlands
We read, with great interest, the paper by Schnohr et al. (1), who investigated the association between jogging and long-term all-cause mortality. The investigators reported that light and moderate joggers had lower mortality rates (hazard ratio [HR]: 0.22; 95% confidence intervals [CI]: 0.10 to 0.47 and HR: 0.66; 95% CI: 0.32 to 1.38, respectively) compared with sedentary nonjoggers, whereas these health benefits were absent in strenuous joggers (HR: 1.97; CI: 0.48 to 8.14). Hence, the investigators concluded that a U-shaped association between exercise dose and all-cause mortality was present, which suggested an upper limit of the health benefits of exercise.
Interestingly, strenuous exercise was established as >4 h of jogging per week at a fast pace. Although this amount of physical activity clearly exceeded the current exercise recommendations, these doses were typically observed in amateur and professional athletes. Other studies investigated the life expectancy of athletic populations. Finnish skiers (2) and world-class endurance athletes (3) demonstrated an increased life expectancy of 2.8 to 6 years compared with reference cohorts. A study that included 15,174 Olympic medallists confirmed these findings, and found 2.8 years of increased life expectancy compared with matched cohorts from the general population (4). Furthermore, a large Swedish study reported a 52% reduction of all-cause mortality among participants of the Vasaloppet cross-country ski-race, with the highest life expectancy found in older participants and athletes who participated in multiple races (5).
These findings suggest that high volumes of exercise training improve longevity and are in contradiction to the U-shaped association between exercise dose and all-cause mortality as suggested by Schnohr et al (1). The small sample size of the strenuous jogger group (n = 40), with only 2 deaths during the 12 years of follow-up, may contribute to these conflicting findings. In addition, the lack of insight into the cause of death may confound the results; if only 1 of the 2 death cases was caused by a non-natural death (e.g., accidents, suicide), the study outcomes would be completely different. Finally, the arbitrarily chosen cutpoints for classification of the light, moderate, and strenuous jogger groups may not appropriately reflect the spectrum of light to extreme doses of exercise training.
Therefore, we believe, that the evidence for an upper limit (>4 h/week) of exercise health benefits and associated all-cause mortality is premature. With physical inactivity as 1 of the most influential risk factors for worldwide morbidity and mortality, we would recommend to keep on running.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2015 American College of Cardiology Foundation
- Schnohr P.,
- O’Keefe J.H.,
- Marott J.L.,
- Lange P.,
- Jensen G.B.
- Clarke P.M.,
- Walter S.J.,
- Hayen A.,
- Mallon W.J.,
- Heijmans J.,
- Studdert D.M.