Exercise and Sudden Death

Physical inactivity is increasingly recognized as modifiable behavioral risk factor for cardiovascular diseases. Available data do not provide clear evidence that withdrawal of physical activity increases coronary artery disease risk, although results from the Harvard Alumni Study suggest that college athletic activity is not protective in later years without lifelong physical activity [1]. Lack of physical activity is among the risk factors that are considered to have adverse effects on the progression of coronary atherosclerosis. Risk of first myocardial infarction was found to be related inversely to energy expenditure reported by 16,936 Harvard male alumni, aged 35–74 years, of whom 572 experienced myocardial infarction in 117,680 person-years of follow-up. Stairs climbed, blocks walked, strenuous sports played all opposed risk. Men with energy expenditure below 2,000 Kcal ⋅ wk−1 were at 64% higher risk than classmates with higher index. Numerous observational studies in both men and women have demonstrated that both regular exercise and physical fitness are associated with reduced risk factors of coronary events and coronary death. Recent epidemiological studies indicate that individuals who maintain a physically active lifestyle are much less likely to develop impaired glucose tolerance and non–insulin-dependent diabetes mellitus. Moreover, it was found that the protective effect of physical activity was strongest for individuals at highest risk of developing non–insulin-dependent diabetes mellitus [2]. Physical inactivity is a major underlying cause of death, disease, and disability. Preliminary data from a World Health Organization study on risk factors suggest that inactivity, or sedentary lifestyle, is one of the ten leading global causes of death and disability [3]. The risk of heart problems due to physical inactivity is related to fitness level and the intensity of the activity performed. For example, someone who is not physically fit is at higher risk for a myocardial infarction during vigorous activity than a person who is physically fit. In the vast majority of the sudden cardiac death cases, the underlying cause is advanced coronary heart disease, which in large proportion of the cases has been asymptomatic and has allowed regular strenuous training. Attempts to prevent the complications by special large-scale screening programs would be ineffective and individual counseling limited by lack of resources [4]. These measures should, however, be used in selected groups and individuals. Even if all available measures at present were used, the cardiovascular complications of physical activity could not be totally prevented. Fortunately, preliminary evidence suggests that at population level, the cardiovascular hazards of physical activity are outweighed by its cardiovascular benefits. Subgroup of patients who are particularly at higher risk of exercise-related sudden death may be identified in different ways, such as pre-participation history taking, physical examination, and/or supplementary cardiac evaluation. Limitations exist because current diagnostic tools are not sufficient to predict a coronary artery plaque with potential risk of disruption and/or an acute thrombotic occlusion. Proper and cost-effective methods for identification of younger subjects with cardiac structural problems or genetic ion channel diseases are still controversial [5]. Physical inactivity is a term used to denote a type of sedentary lifestyle that includes less than 150 min of moderate physical activity or less than 60 min of vigorous physical activity per week [6]. Sedentary lifestyle includes little or no vigorous physical exercise which contributes to many preventable causes of death. Cardiovascular diseases remain the biggest cause of deaths worldwide. Premature deaths from cardiovascular disease range from 4% in high-income countries to 42% in low-income countries. In recent years, cardiovascular risk in women has been increasing and has killed more women than breast cancer. Rainwater et al. [7] demonstrated that vascular injury accumulates from adolescence, making primary prevention efforts necessary from childhood. By the time that heart problems are detected, the underlying cause, that is, atherosclerosis, is usually significantly advanced, having progressed for decades. There is therefore increased emphasis on preventing atherosclerosis by modifying risk factors, such as healthy eating and exercise.