To examine the risk of primary cardiac arrest during vigorous exercise, we interviewed the wives of 133 men without known prior heart disease who had had primary cardiac arrest. Cases were classified according to their activity at the time of cardiac arrest and the amount of their habitual vigorous activity. From interviews with wives of a random sample of healthy men, we estimated the amount of time members of the community spent in vigorous activity. Among men with low levels of habitual activity, the relative risk of cardiac arrest during exercise compared with that at other times was 56 (95 per cent confidence limits, 23 to 131). The risk during exercise among men at the highest level of habitual activity was also elevated, but only by a factor of 5 (95 per cent confidence limits, 2 to 14). However, among the habitually vigorous men, the overall risk of cardiac arrest--i.e., during and not during vigorous activity--was only 40 per cent that of the sedentary men (95 per cent confidence limits, 0.23 to 0.67). Although the risk of primary cardiac arrest is transiently increased during vigorous exercise, habitual vigorous exercise is associated with an overall decreased risk of primary cardiac arrest.
PIP: The risk of cardiac arrest during vigorous exercise is examined in the context of the relationship between the risk of cardiac arrest and vigorous exercise in general. The data concern 133 men who had primary cardiac arrest in Washington State between 1979 and 1981 and a control group of healthy men. The data were obtained through interviews with the men's wives. The results indicate that the risk of cardiac arrest during exercise is higher than at other times, especially among those with low levels of habitual activity; however, among habitually vigorous men, the overall risk of cardiac arrest (during and not during vigorous activity) is only 40 percent that of sedentary men.