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.
Expert Comment
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 <1-hour group, 4 in the 1- to 2.4-hours group, 3 in the 2.5- to 4-hours group, and 1 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.
Journal of the American College of Cardiology
Jogging and Long-Term Mortality: The Copenhagen City Heart Study