Physical inactivity as a lethal factor in myocardial infarction among men

Invited Commentary: Is Strenuous Activity Good for You? The Legacy of Ralph Paffenbarger

Ralph Paffenbarger, Jr, MD, DrPH (1922-2007), was initially trained as an infectious disease epidemiologist at the Johns Hopkins School of Hygiene and Public Health (now the Bloomberg School of Public Health). He was the first Epidemiology Intelligence Service officer in the first Epidemiology Intelligence Service class. He joined the National Heart Institute (now the National Heart, Lung, and Blood Institute) in its very early days and later became a faculty member at Stanford University and Harvard University. His studies of the relationships between physical activity (PA) and coronary heart disease in longshoremen and in college athletes at Harvard University and University of Pennsylvania, as well as the follow-up of the Harvard College students to evaluate PA both in and after college that was detailed in the article "Physical Activity as an Index of Heart Attack Risk in College Alumni" (Am J Epidemiol. 1978;108(3):161-175), established that more strenuous PA reduced the risk of heart attack and that it was necessary to continue PA after college. Results from his studies suggested that less strenuous PA had little effect on risk of heart attacks. He was a strong advocate for the importance of PA in the prevention of heart attacks and as a public health recommendation and for the idea that adherence to strenuous PA over the course of a lifetime was difficult. He was a marathon runner who competed frequently in the Boston Marathon and practiced what he preached.

Characteristics of representative male survivors of myocardial infarction compared with representative population samples

A series of 299 men, aged 27-67, who had survived their first myocardial infarction (MI), have been compared with representative population samples with respect to tobacco consumption, alcoholic intemperance, physical activity during work and leisure time, occurrence of hypertension, and cholesterol and triglyceride levels in serum. The infarction patients comprised 90% of all surviving, diagnosed cases of primary MI in men aged 67 years or below during 1968-70 in Göteborg, Sweden. The comparison between infarction patients and general population samples revealed that the patients smoked more, and were less physically active during leisure time but not during work. They had more often a positive history of hypertension and treatment for high BP and their serum cholesterol and serum triglyceride values were higher. For all these variables the difference decreased with increasing age and was generally not statistically significant above the age of 60 years. Alcoholic intemperance was more common among infarction patients who died outside hospital, but there was no difference in this respect between surviving patients and the general population.

The behavioral determinants of exercise: implications for physical activity interventions

In light of the well-documented health benefits of physical activity and the fact that the majority of adult men and women are inactive, promoting regular physical activity is a public health priority. This chapter reviews current research findings regarding the determinants of exercise behavior. It also discusses the implications of this knowledge for individual and public health recommendations and intervention strategies for promoting physical activity. The discussion is predicated on the belief that physical activity is a complex, dynamic process. During their lives, individuals typically move through various phases of exercise participation that are determined by diverse factors. This chapter discusses physical activity determinants in two broad categories: individual characteristics, including motivations, self-efficacy, exercise history, skills, and other health behaviors; and environmental characteristics such as access, cost, and time barriers and social and cultural supports.

The assessment of physical activity by leisure-time physical activity questionnaires

The assessment of physical activity by questionnaire is currently the most popular and practical method of quantifying physical activity levels. Many questionnaires, past and present, have considered overall or habitual physical activity, which includes occupational (or nonleisure) activity. Others have focused specifically on leisure-time physical activity (LTPA) owing to the recognition of its dominating contribution to the total physical activity of developed populations. This review covers questionnaires that wholly or in part attend to LTPA levels. Typically, self-complete or interviewer-administered questionnaires record information on the types, frequency and duration of activities performed over a particular period of time. Activity-specific energy cost values, expressed in metabolic equivalents (METS) or kilocalories, are then commonly used to estimate the total energy expenditure from all activities and/or categories of activities. The validation of LTPA questionnaires has had to rely upon indirect methods, such as the assessment of cardiorespiratory fitness, body composition and activity diaries. The reporting of the reliability of questionnaires has frequently been ignored, although in cases where it has been reported, doubt exists as to whether the consistency of the questionnaire or the consistency of subjects' physical activity habits were being examined. LTPA questionnaires first appeared in the literature in the mid-1960s for use among specific, mainly middle-aged male population groups. Though they varied in their modes of scoring, periods of activity recall, and overall complexity, associations were universally observed between physical activity levels and chronic health conditions. However, it became apparent that different questionnaires did not yield the same results. In 1978, a questionnaire to assess only LTPA, the Minnesota LTPA Questionnaire, was published and despite its substantial limitations, has since established itself as the most popular option available. In recent years, shorter and simpler alternatives have been advocated, though most have yet to be adequately scrutinised. Associations have been found between LTPA and fitness levels, prompting the use of LTPA questionnaires in large-scale fitness surveys of both adults and children. Although LTPA has continued to be estimated in terms of energy expenditure, little attempt has been made to extend existing knowledge on the energy cost of physical activities. Existing values do not accommodate for individual intensities and inter-population activity variations. Consequently, standardised questionnaires are not yet viable. There exists considerable scope for further work with LTPA questionnaires, especially since the association between coronary heart disease and physical activity is now well recognised. Efforts ought to be directed at wider social groups for whom leisure-time activity may have distinct implications.

Treatment of hypertension in the elderly

Investigation of preventive measures for hypertension and atherosclerosis is a geriatric medicine priority. While the causes of both isolated systolic hypertension and conventional systolic and diastolic hypertension in the elderly are well defined, the benefits of lowering blood pressure are not. Evidence to support the treatment of symptomatic hypertension is convincing for men 60 years of age; it is not for women in this age group. The need to treat hypertension, particularly isolated systolic hypertension in patients above 75 years old, is still not resolved. Isolated systolic hypertension in older patients is at least as strong a risk factor for cardiovascular disease as is diastolic hypertension. Ongoing trials may answer these questions; in the meantime, drug therapy in this group will vary widely. The elderly hypertensive is more likely than the younger hypertensive to have other diseases; diagnosis of these disorders is crucial. Hypertension arising de novo late in life warrants a search for underlying and possibly remedial causes. Antihypertensive drug therapy to relieve symptoms is difficult to justify, because most elderly hypertensive patients are asymptomatic; however, it has been shown to delay morbid and fatal complications of hypertension. Appropriate therapy for the elderly hypertensive must be individualized and should be associated with few or no side effects. The thiazides are the preferred diuretics for long-term treatment of hypertension in the elderly. Beta blockers are attractive because they are cardioprotective, counter the end organ effect of catecholamines and reduce angina; however, some decrease cardiac output, increase peripheral resistance, decrease renal blood flow and cause fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)

Physical activity levels and coronary heart disease. Analysis of epidemiologic and supporting studies

Coronary heart disease, the primary health problem in western life, is caused by the interaction of multiple factors. Absolute proof of the contributing role of physical inactivity is not possible owing to the complexity of the CHD problem and the infeasibility of a definitive clinical trial because of logistical and economic constraints. Despite limitations, existing epidemiologic studies strongly suggest, but fall short of proving, the concept that habitual physical exercise offers partial protection against primary or secondary events of CHD and associated mortality. However, experimental data support this hypothesis and provide evidence of possible mechanisms responsible for the protection. The available epidemiologic data also suggest that physical inactivity is probably not as potent an individual risk factor as elevated serum cholesterol levels, hypertension, and cigarette smoking, and that the protective effects of exercise may be overwhelmed by high levels of these major risk factors. On the other hand, there is some evidence that exercise may attenuate other risk factors both directly and through associated weight reduction. Epidemiologic studies also suggest a dose response relationship between physical activity and rates of CHD. About 2000 kcal per week of moderate intensity, dynamic, endurance-type of exercise (such as walking or jogging about 20 miles per week) or at least one hour of intermittent hard physical labor are required to obtain the optimal effect of exercise on coronary heart disease rates. Experimental studies suggest that this amount of exercise should provide sufficient stimulus to favorably alter blood HDL cholesterol levels and perhaps other CHD risk factors, especially if there is an accompanying reduction in weight. Possible mechanisms for the protective effects of exercise against CHD are illustrated in Figure 1. Insistence on final experimental proof prior to prudent medical practice or public health policy on physical inactivity or other coronary risk factors indicates a lack of understanding of the nature of scientific proof and evidence required for health actions.(ABSTRACT TRUNCATED AT 400 WORDS)

High density lipoprotein and apolipoprotein A-i during physical inactivity. Demonstration at low levels in patients with spine fracture

Lack of physical activity appears to have deleterious effects on serum lipoproteins. Twenty-three patients who were completely immobilised by traumatic fracture of the spine had significantly lower (P < 0.001) plasma high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I levels than normally mobile paired control subjects. The low density lipoprotein cholesterol (LDL-C) levels of the immobile patients were not different from those of controls but the LDL triglyceride (LDL-TG) of the patients was increased. The patients had a significantly higher LDL/HDL-C ratio and HDL-C/apoprotein A-I ratio than the controls. These results suggest that the increased risk of ischemic heart disease in physically inactive people is partially accounted for by low plasma HDL levels. On the other hand, caution is needed in the interpretation of HDL findings in clinical conditions where the physical activity of the patients is limited.

Relation of lipids, weight and physical activity to incidence of coronary heart disease: the Puerto Rico heart study

The 2 1/2 year incidence of coronary heart disease was examined in relation to antecedent serum cholesterol and fasting triglyceride levels, physical activity status and relative weight in a cohort of 8,171 urban and rural men 45 to 64 years old participating in the Puerto Rico Heart Program. In this population with a low incidence rate of coronary heart disease, risk of coronary disease was related to serum cholesterol in both urban and rural groups, but this trend was statistically significant only in the urban population. Neither the urban nor the rural population showed a substantial or statistically significant association of serum triglyceride levels with incidence of coronary heart disease. Correlations among relative weight and serum triglyceride and serum cholesterol levels were noted. Despite small differences in incidence of coronary heart disease between urban and rural groups, values for serum cholesterol, triglycerides and relative weight were all significantly higher in the urban men. Only physical activity levels were higher in the rural men. Multivariate analysis, performed to sort out the net effects of these interrelated variables, revealed that serum cholesterol is related to the risk of coronary heart disease even when all variables are taken into account. Low levels of physical activity were significantly associated with a greater incidence of coronary heart disease only in urban men (P less than 0.05). Overweight, which was associated with higher lipid values and less physical activity, was not related to the development of coronary heart disease in either the urban or the rural cohort.

Physical exercise and the prevention of atherosclerosis and cholesterol gall stones

There is accumulating evidence in man and experimental animals that even mild exercise, if regularly repeated, may alter the metabolism of lipids. Exercise has been reported as decreasing peripheral tissue cholesterol in red blood cells, working muscle, lungs and the liver. During physical activity, the output of cholesterol and bile acids into the bile increases. This probably leads to higher faecal losses of sterols which may lead to lower cholesterol levels in the peripheral tissues and in the bile, when exercise is repeated regularly. Preferential release of unsaturated fatty acids from the adipose tissue during exercise and the linoleic acid-dependent LCAT enzyme (transporting plasma cholesterol) may be partly responsible for this effect of exercise. The experimental data reviewed provide supportive basis for epidemiological studies reporting on the beneficial effect of regular exercise.

Physical activity is an important factor in the phylogeny of all animal species, secondary only to food intake and reproduction. Exercise is readily available to all population groups. There is good evidence that the amount of exercise required for a protective effect is easily accessible for time-pressured and older individuals. Short bursts of activity repeated several times a day may be equally or more beneficial than prolonged exhaustive exercise. Modified exercise is also beneficial for patients with coronary heart disease and for elderly patients, provided this is done under strict medical supervision. To be effective, physical exercise should be regular and continuous throughout life.

[Physical activity and coronary heart disease prevention]

Numerous reports indicate that physical inactivity is one of the coronary risk factors; however, proof that exercise has a protective effect is still elusive. Nevertheless, to continue the existing controversy on the prophylactic value of physical activity seems to be inappropriate. On the one hand, a controlled trial is not feasible; on the other hand, physical activity is a physiological function that should be promoted anyway, regardless whether irrefutable evidence of its value in the prevention of coronary heart disease is available. Activity starting in childhood and continuing throughout life is a safe approach. In more general terms, habitual physical activity should be re-introduced into the pattern of life of contemporary society.

Incidence and presentation of myocardial infarction in North Karelia, Finland

A myocardial infarction (mi) register was started on May 1, 1972 in the county of North Karelia in Eastern Finland as a part of the North Karelia project. Information about all cases with a suspected acute MI among the North Karelian population are collected by the register. The principles of the register follow the recommendations of the WHO expert working group. Altogether 713 cases were registered between May 1, and Dec. 31,1972. The distribution of them into diagnostic categories was: "definite" 57%, "possible" 30%, "no acute MI" 8% and "insufficient information" 5%. Patients with no acute MI have been excluded in the results. About 47% of the male patients below 65 years had a history of previous MI. Most of the patients in the group had been heavy cigarette smokers, eating mainly butter as the fat in their diet. Overweight was rare among the male patients but not among the females. During the years preceding the attack, most of the patients had visited a physician and a pathological ECG had been recorded. The average time delay before hospital treatment was internationally relatively short. The 4 week fatality rate among patients below 65 years was 37% for males and 35% for females. These rates were slightly lower than those in the register material in Helsinki. The annual incidence rate per thousand for the age group 30-64 in North Karelia was 13.8 among males and 2.6 among females. The incidence rate increased continuously with age among males,among females it increased markedly only after the age of 60. The risk ratio between North Karelia and Helsinki for the age standardized incidence rates of males in the age group 30-64 was 1.38, and for respective mortality rates 1.21. Within North Karelia the highest incidence rate for males aged 30-64 was recorded in the rural area of Ilomantsi-Tuupovaara in the East.

Detection of individual susceptibility toward coronary disease

Current views on the usefulness of pre-clinical markers to detect susceptibility toward coronary heart disease have been presented, including the role of the hyperlipidemias, hypertension, hyperglycemia, obesity, family history and several other personal attributes. In addition, various clinical, electrocardiographic and other indices of early clinical disease serve as premonitory warning signals toward myocardial infarction and sudden death. Individuals harboring one or more of these risk factors should be detected and protected by means of preventive measures.

Physical activity, body fat and experimental cardiac necrosis

1. The effects of varying levels of physical activity were tested in rats, starting at ages of 21, 32 and 55 days and continuing until go, 100, 125 and 205 days.

2. Weight changes did not differ significantly between the exercise groups, except in the groups tested up to 205 days, when both the exercised group and the group with limited activity were significantly lighter than the control group.

3. The weight of the soleus muscle was significantly greater in the exercised rats compared with controls and rats with limited activity, except in the oldest age-group. The weight of the tibialis anticus muscle did not differ significantly between the different exercise regimes.

4. Heart weight was not significantly affected by the exercise regime, except that in rats studied from 55 to 125 days; the group with limited activity had significantly lighter hearts than those in the control group or the exercised group.

5. The percentage body fat was lower in the exercised group compared with the limited activity group, and was less than the control group in both the rats studied up to 205 days and those studied from 21 to 90 days.

6. Isoprenaline produced less cardiac damage in the exercised rats than in controls or in rats with limited activity. Animals who died following injection of isoprenaline had a higher percentage body fat than those animals with minimal cardiac damage.