University of South Carolina Columbia, South Carolina, U.S.A.
Mark Tarnopolsky, MD, PhD
Schnohr P, Parner J, Lange P. Mortality in joggers: population based study of 4,658 men. BMJ 2000;321:602–603.
ObjectiveDoes Jogging Increase Mortality in Men?
To investigate whether regular jogging is associated with increased mortality in men.
DesignDoes Jogging Increase Mortality in Men?
Cohort study of a randomly drawn population sample, during the period 1976 to 30 November 1998.
SettingDoes Jogging Increase Mortality in Men?
The Copenhagen City Heart Study in Denmark.
ParticipantsDoes Jogging Increase Mortality in Men?
The cohort comprised 4,658 men (response rate 72%) aged 20 to 79 years, who had no previous myocardial infarction and who attended 2 examinations in 1976 to 1978 and 1981 to 1983.
Assessment of risk factorsDoes Jogging Increase Mortality in Men?
Jogging status was ascertained at both baseline examinations by asking the men whether they were joggers. Additional risk factors that were measured were systolic blood pressure, plasma cholesterol concentrations, body mass index, presence of diabetes, smoking status, household income, years of education, and alcohol consumption.
Main outcome measureDoes Jogging Increase Mortality in Men?
The outcome measure was the occurrence of death. Information was obtained from the Danish national population register, which is considered to be almost 100% complete.
Main resultsDoes Jogging Increase Mortality in Men?
At the first examination 217 men (4.7%) reported jogging. At the second examination 96 (2.1%) of these men were still actively jogging and 106 men (2.3%) had started jogging. 4335 men (93%) were nonjoggers at both examinations. Crude estimates of death rates showed a higher mortality among nonjoggers and a lower mortality among persistent joggers. In age-adjusted Cox proportional hazards regression analysis, an effect of jogging was found only for the group that were persistent joggers (relative risk of death 0.37; 95% CI, 0.19 to 0.71) compared with nonjoggers. Compared with nonjoggers and joggers at only 1 examination, relative risk for death among persistent joggers was 0.39 (CI, 0.19 to 0.73). Presence of diabetes, smoking, low household income, and abstaining from alcohol or consuming >21 alcoholic drinks per week conferred a greater risk of death, whereas 10 years or more of education reduced risk.
ConclusionDoes Jogging Increase Mortality in Men?
Regular jogging was associated with decreased mortality in Danish men, independently of other risk factors.
Source of funding: Danish Heart Foundation.
Correspondence to: Dr. P. Schnohr, Copenhagen City Heart Study, Epidemiological Research Unit, Copenhagen University Hospital, Bispebjerg DK-2400 Copenhagen N, Denmark. E-mail: email@example.com
CommentaryDoes Jogging Increase Mortality in Men?
The prospective, epidemiological study by Schnohr et al. of men in Copenhagen, Denmark, found that those who reported being joggers both at baseline and five years later were less likely to die during the ensuing 15 years than those who did not report being joggers. This observation may seem unremarkable, because several studies have previously reported that higher levels of physical activity and fitness are associated with reduced risk of mortality in adults. Nonetheless, this study is noteworthy for at least one reason. The authors examined the relationship between mortality and a specific form of physical activity—jogging. Most previous studies have used global measures of physical activity, and such measures are known to have limited validity. An advantage to studying a specific form of vigorous physical activity is that subjects are able to report their participation with good validity, thus misclassification of subjects should be minimal.
Typically adults participate regularly in a limited number of modes of structured exercise; persons tend to think of themselves as “tennis players,” “aerobic dancers,” or “joggers,” not generic exercisers. A further advantage to studying a specific form of physical activity is that the findings of this study apply specifically to jogging and suggest that participants in that activity experience important health benefits.
It is also important to note that the analysis of the data did not include statistical adjustment for participation in other forms of physical activity. Undoubtedly the nonjogging reference group included many persons who were physically active in other forms of exercise. The benefits of jogging found in this study may, therefore, be less than would be observed if joggers were compared with a sedentary reference group.
As knowledge of the relationship between physical activity and health grows, we need to learn more about dose–response issues. Understanding the health effects of specific modes of physical activity is as important as understanding various intensities and durations of exercise. The focus on a single activity by Schnohr et al. exemplifies the type of study of which many more are needed.