February 10, 2015
Journal of the American College of Cardiology
TAKE-HOME MESSAGE
- The association between jogging and mortality was evaluated by following 1098 healthy joggers and 3950 healthy non-joggers. Lowest mortality was associated with 1 to 2.4 hours of jogging per week, no more than three times per week, and slow and average pace. When grouped into light, moderate, or strenuous joggers based on quantity, frequency, and pace, light joggers were associated with lowest mortality, followed by moderate joggers. Strenuous joggers were not statistically different from sedentary non-joggers.
- Light to moderate joggers had a lower mortality compared with sedentary but healthy joggers. Conversely, strenuous joggers are statistically similar in mortality to non-joggers.
Cardiology
Written by Paul D Thompson MD
Can lots of exercise be too much of a good thing?
Earlier results from the Copenhagen Heart Study1 demonstrated that men who classified themselves as joggers lived 6.2 years longer than their more sedentary counterparts and that women joggers lived 5.6 years longer. Despite such positive results, several recent studies have suggested that with exercise there may be a point of too much of a good thing. Investigators have shown patchy late gadolinium enhancement in the right ventricles of lifelong endurance athletes2 and have even found increased coronary atherosclerosis in men who have run multiple marathons over their lifetimes.3 The key question is whether increasing amounts of exercise have diminishing returns or even increased risk.
Researchers from the Copenhagen Heart Study reexamined their data to look at this possibility. They examined Danish national death records to determine mortality in 1098 joggers and 413 non-joggers followed since 2001. They divided the joggers by hours per week, days per week, and the speed of their jogging. The results suggest that less is better. Jogging 1 to 2.4 hours weekly had the lowest mortality rate compared with that of the non-joggers, but the rate increased progressively with 2.5 to 4 hours and >4 hours of jogging. Similarly jogging 2 to 3 times per week had a lower mortality rate than >3 times weekly, and slow jogging had a lower mortality rate than moderate and fast jogging.
This report adds to other provocative papers on the subject of whether or not one can get too much exercise. Interestingly, some studies suggest that the greatest cardiovascular risk comes from sitting and that just standing reduces risk. These data from the Copenhagen Heart Study support the idea that one gets the most benefit from very low doses of exercise. The Copenhagen results do not indicate risk from too much exercise, but rather lack of benefit. The present Copenhagen study and many similar studies have one major flaw: there are few individuals in the highest exercise groups, leaving few cases for analysis. For example, in the present Copenhagen study, there were only 20 deaths in the 4-hours per week group. This means that small changes can have a profound impact on the results.
Despite this limitation, the possibility that too much exercise might be too much of a good thing deserves consideration. Where there is smoke, there is usually some fire.
References
- Schnohr P, Marott JL, Lange P, Jensen GB. Longevity in male and female joggers: the Copenhagen City Heart Study. Am J Epidemiol. 2013;177(7):683-689. http://aje.oxfordjournals.org/content/177/7/683.long
- La Gerche A. Can intense endurance exercise cause myocardial damage and fibrosis? Curr Sports Med Rep. 2013;12(2):63-69. http://journals.lww.com/acsm-csmr/pages/articleviewer.aspx?year=2013&issue=03000&article=00008&type=abstract
- Schwartz RS, Merkel Kraus S, Schwartz JG, et al. Increased coronary artery plaque volume among male marathon runners. Missour Med. 2014;111(2):85-90. http://www.dementiatoday.com/increased-coronary-artery-plaque-volume-among-male-marathon-runners/
Abstract
BACKGROUND
People who are physically active have at least a 30% lower risk of death during follow-up compared with those who are inactive. However, the ideal dose of exercise for improving longevity is uncertain.
OBJECTIVES
The aim of this study was to investigate the association between jogging and long-term, all-cause mortality by focusing specifically on the effects of pace, quantity, and frequency of jogging.
METHODS
As part of the Copenhagen City Heart Study, 1,098 healthy joggers and 3,950 healthy nonjoggers have been prospectively followed up since 2001. Cox proportional hazards regression analysis was performed with age as the underlying time scale and delayed entry.
RESULTS
Compared with sedentary nonjoggers, 1 to 2.4 h of jogging per week was associated with the lowest mortality (multivariable hazard ratio [HR]: 0.29; 95% confidence interval [CI]: 0.11 to 0.80). The optimal frequency of jogging was 2 to 3 times per week (HR: 0.32; 95% CI: 0.15 to 0.69) or ≤1 time per week (HR: 0.29; 95% CI: 0.12 to 0.72). The optimal pace was slow (HR: 0.51; 95% CI: 0.24 to 1.10) or average (HR: 0.38; 95% CI: 0.22 to 0.66). The joggers were divided into light, moderate, and strenuous joggers. The lowest HR for mortality was found in light joggers (HR: 0.22; 95% CI: 0.10 to 0.47), followed by moderate joggers (HR: 0.66; 95% CI: 0.32 to 1.38) and strenuous joggers (HR: 1.97; 95% CI: 0.48 to 8.14).
CONCLUSIONS
The findings suggest a U-shaped association between all-cause mortality and dose of jogging as calibrated by pace, quantity, and frequency of jogging. Light and moderate joggers have lower mortality than sedentary nonjoggers, whereas strenuous joggers have a mortality rate not statistically different from that of the sedentary group.