I HOPE people who wish to engage in more high-intensity exercise will not be discouraged from doing so after reading last Wednesday's article ("Light jogging best for long life: Study"), which reported that people jogging at a slow or moderate pace had the lowest rates of death, while those who jogged frequently and strenuously were just as likely to die as people who did not jog at all.
It has been well established that physical activity decreases the risk of chronic disease and early death.
It is also well documented that physical activity of longer duration or high intensity is associated with additional health benefits, although the effect of extreme sports is less clear.
The recent report is based on a sub-study of the Copenhagen City Heart Study, and tracked 1,098 healthy joggers and 413 healthy non-joggers.
Jogging is certainly not as popular as cycling in Copenhagen, where the study was based. Indeed, in order to look at just jogging, the reported study excluded the 3,537 active non-joggers who were also part of the larger study. Importantly, while the study adjusted for other factors like age, smoking, alcohol intake and certain chronic diseases, it did not report if it adjusted for other physical activities in the joggers.
Conceivably, those who jogged infrequently may also participate in other physical activities for leisure, work or when commuting.
The way the study categorised doses of jogging is arbitrary and there were only 47, or 4 per cent of the 1,098 joggers with the highest jogging time of more than four hours per week where no mortality benefits were found.
There were only two persons out of the 47 who died in the 12-year follow-up period - we do not know the reason for these deaths.
Because there are so many confounding factors that are difficult to account for, one has to consider the result of an epidemiological study carefully.
When new research offers data that conflicts with other academic literature, its methodology should be examined more closely.
Indeed, some studies published in the most reputable journals have later been shown to be not reproducible or less conclusive than previously thought.
Wee Shiou Liang (Dr)
It has been well established that physical activity decreases the risk of chronic disease and early death.
It is also well documented that physical activity of longer duration or high intensity is associated with additional health benefits, although the effect of extreme sports is less clear.
The recent report is based on a sub-study of the Copenhagen City Heart Study, and tracked 1,098 healthy joggers and 413 healthy non-joggers.
Jogging is certainly not as popular as cycling in Copenhagen, where the study was based. Indeed, in order to look at just jogging, the reported study excluded the 3,537 active non-joggers who were also part of the larger study. Importantly, while the study adjusted for other factors like age, smoking, alcohol intake and certain chronic diseases, it did not report if it adjusted for other physical activities in the joggers.
Conceivably, those who jogged infrequently may also participate in other physical activities for leisure, work or when commuting.
The way the study categorised doses of jogging is arbitrary and there were only 47, or 4 per cent of the 1,098 joggers with the highest jogging time of more than four hours per week where no mortality benefits were found.
There were only two persons out of the 47 who died in the 12-year follow-up period - we do not know the reason for these deaths.
Because there are so many confounding factors that are difficult to account for, one has to consider the result of an epidemiological study carefully.
When new research offers data that conflicts with other academic literature, its methodology should be examined more closely.
Indeed, some studies published in the most reputable journals have later been shown to be not reproducible or less conclusive than previously thought.
Wee Shiou Liang (Dr)
