62
PRIMARY PREVENTION OF HEART ATTACK* J. N. MORRIS, M.D. (Hon.), F.R.C.P. Social Medicine Unit Medical Research Council Department of Community Health London School of Hygiene London, England
IT is rather embarrassing to be addressing an audience in the United States on the primary prevention of coronary heart disease because so much of the research in this field has been done in this country. Moreover, I am going to say little about the American health situation because I do not feel qualified to speak about it. I hope that when I examine Great Britain you will see some of your own problems projected, at least in miniature, and perhaps this will be interesting and useful. A MASS DISEASE Let me start with a word on frequency, as it is important to get this in perspective. Coronary heart disease is the leading cause of premature, untimely death in men in both Great Britain and the United States. Perhaps as much as a third of the deaths occurring in those less than 65 or 70 years of age are caused by coronary heart disease. However, it is the morbidity that is revealing. First, an average of one man in five in Great Britain-in the United States probably one man in four-may be expected to develop clinical coronary heart disease during middle age. The figures for old age are less adequate, but there is good reason to believe that the incidence continues to rise; by 70 years of age perhaps one man in four in Great Britain has shown clinical coronary heart disease and in the United States perhaps one in three. Subclinical disease -as estimated by the prevalence in population surveys of anginal effort pain and of minor ischemic changes on the electrocardiogram (ECG)is perhaps two or three times commoner than clinical incidence. And *Presented in a panel, Strategies for Prevention: Cancer and Heart Disease, as part of the 1974 Annual Health Conference of the New York Academy of Medicine, Prevention and Health llMaintentanice Revisited, April 25 and 26, 1974.
Bull. N. Y. Acad. Med.
PRIMARY PREVENTION OF HEART
ATTACK
63
finally, of course, the underlying atherosclerosis of the coronary arteries is virtually universal among middle-aged men in Britain, and from what data I have seen the position is not very different in the United States. We are indeed dealing with a mass disease in the literal meaning of the wordy' That it is so common, so ubiquitous, has profound meaning for etiology, the search for causes, and looking ahead to our main concern today, prevention. For a start, coronary disease cannot be caused by deviant behavior or exceptional stresses. It must arise out of mass behavior. That it must be a disease of the everyday living of ordinary people is most simply exemplified by one or two facts on diet. In every study that has been done in England, whether of national statistics or smallscale clinical surveys, the ratio of saturated to polyunsaturated fatty acids in the diet ranges between 5:i and 2.5: I.4 Most experts today would agree that we should aim at a ratio closer to 2: I or I: I. That is to say, almost every adult in England is on a suboptimal diet-this relates to the point about mass disease. Diet also illustrates a second feature of this modem dilemma. On this plane of nutrition, apparently similar individuals eating the same amount of fat each have concentrations of plasma cholesterol ranging all the way from less than 200 to well over 300 mg.%-with profound implications for their future." (Of course, the saturated-fat component of the diet is only one factor affecting levels of blood lipids, but it is probably the main dietary factor.) Thus, it is possible to say that coronary disease is not merely a disease of ordinary people, but a disease of ordinary people who cannot tolerate ordinary ways of living and cannot adapt healthfully to the prevailing habits of our society. We know exceedingly little of what underlies this individual variation, either in terms of genetics or of environmental factors. Very little indeed is understood about it at the physiological level; this is a major neglected area for research.
TAKING STOCK We shall now discuss the 25 years of modern research into the etiology of coronary heart disease and the guidelines to prevention. I shall mention only some of the principal features. Two main sets of risk factors that predict future disease in the ordinary population have been identified.7' 8 Vol. 51, No. 1, January 1975
64
J. N. MORRIS
TABLE I. VIGOROUS EXERCISE (YE) IN LEISURE-TIME REPORTED BY MALE EXECUTIVE-GRADE CIVIL SERVANTS AGED 40 TO 65. SAMPLE FRIDAY AND SATURDAY 1968-1970 Form of VE
Examples
Active recreations*
Swimming
Keeping fit* Vigorous getting about*
Hill-climbing Dancing (spec.) Morning exercises Brisk walking
Heavy workt Gardening
"Do it yourself" Other
Climbing stairs
or
jogging
Running Cycling (spec.) Digging; felling trees; clearing brush Building in stone or concrete Moving heavy objects (spec.) Major (rusted) car repairs
450+ daily4
*Period of at least five minutes.
tPeriod of more than one half hour; or total of one hour or more in the two days. +Empirical observation. VE = vigorous exercise, involving an expenditure of at least 71/2 kilocals per minute.
Reproduced by permission from Morris, J. N., Adam, C., Chave, S. P. W., Sirey, C., Epstein, L., and Sheehan, D. J.: Vigorous exercise in leisure-time and the incidence of coronary heart disease. Lancet 1:333, 1973.
First, there is a set of behavior patterns. Overweight, smoking cigarettes, and inadequate exercise are the three main predictive factors that have been identified. I shall pause here to discuss exercise; it happens to be my own main research interest and it is another largely neglected area of research. Inadequate exercise as a risk factor. We became interested in exercise as a possible factor in coronary heart disease back in I949 when it was noticed that the conductors on London's buses had substantially fewer heart attacks and coronary deaths than the drivers of these vehicles.9' 10 These buses are double deckered: i.e., the conductor who takes the money and looks after the passengers has an active occupation and climbs many steps while the driver's is a typically sedentary job. Similar observations were made among other occupations which carried further into the morbid anatomy of the disease. In recent years, however, the social medicine unit of the Medical Research Council has lost interest in this kind of study. Importantly, if exercise is of value for health, in the future it will have to be the exercise that people take in their leisure time, because physical activity is steadily being eliminated from work. Even conservative projections of the year 2000 show almost the entire population deprived of any substantial physical effort in their work. Bull. N. Y. Acad. Med.
65
PRIMARY PREVENTION OF HEART ATTACK
TABLE II. PHYSICAL ACTIVITY IN LEISURE-TIME AND THE INCIDENCE CLINICAL ATTACKS) OF CORONARY HEART DISEASE (FIRST AMONG MALE BRITISH CIVIL SERVANTS AGED 40 TO 45 Vigorous exercise (VE)* Active recreation Keeping fit Vigorous getting about Heavy work Climbing 450+ stairs p.d. Men reporting VE (Expected)
First clinical attackst (238 mnen)
Matched controls (476 men)
5 3
19 16 21 78
1 19
0 25 (60)
8 120
*During the two days in 1968 to 1970; see Table I for definitions. to 1972. P
PRIMARY PREVENTION OF HEART ATTACK* J. N. MORRIS, M.D. (Hon.), F.R.C.P. Social Medicine Unit Medical Research Council Department of Community Health London School of Hygiene London, England
IT is rather embarrassing to be addressing an audience in the United States on the primary prevention of coronary heart disease because so much of the research in this field has been done in this country. Moreover, I am going to say little about the American health situation because I do not feel qualified to speak about it. I hope that when I examine Great Britain you will see some of your own problems projected, at least in miniature, and perhaps this will be interesting and useful. A MASS DISEASE Let me start with a word on frequency, as it is important to get this in perspective. Coronary heart disease is the leading cause of premature, untimely death in men in both Great Britain and the United States. Perhaps as much as a third of the deaths occurring in those less than 65 or 70 years of age are caused by coronary heart disease. However, it is the morbidity that is revealing. First, an average of one man in five in Great Britain-in the United States probably one man in four-may be expected to develop clinical coronary heart disease during middle age. The figures for old age are less adequate, but there is good reason to believe that the incidence continues to rise; by 70 years of age perhaps one man in four in Great Britain has shown clinical coronary heart disease and in the United States perhaps one in three. Subclinical disease -as estimated by the prevalence in population surveys of anginal effort pain and of minor ischemic changes on the electrocardiogram (ECG)is perhaps two or three times commoner than clinical incidence. And *Presented in a panel, Strategies for Prevention: Cancer and Heart Disease, as part of the 1974 Annual Health Conference of the New York Academy of Medicine, Prevention and Health llMaintentanice Revisited, April 25 and 26, 1974.
Bull. N. Y. Acad. Med.
PRIMARY PREVENTION OF HEART
ATTACK
63
finally, of course, the underlying atherosclerosis of the coronary arteries is virtually universal among middle-aged men in Britain, and from what data I have seen the position is not very different in the United States. We are indeed dealing with a mass disease in the literal meaning of the wordy' That it is so common, so ubiquitous, has profound meaning for etiology, the search for causes, and looking ahead to our main concern today, prevention. For a start, coronary disease cannot be caused by deviant behavior or exceptional stresses. It must arise out of mass behavior. That it must be a disease of the everyday living of ordinary people is most simply exemplified by one or two facts on diet. In every study that has been done in England, whether of national statistics or smallscale clinical surveys, the ratio of saturated to polyunsaturated fatty acids in the diet ranges between 5:i and 2.5: I.4 Most experts today would agree that we should aim at a ratio closer to 2: I or I: I. That is to say, almost every adult in England is on a suboptimal diet-this relates to the point about mass disease. Diet also illustrates a second feature of this modem dilemma. On this plane of nutrition, apparently similar individuals eating the same amount of fat each have concentrations of plasma cholesterol ranging all the way from less than 200 to well over 300 mg.%-with profound implications for their future." (Of course, the saturated-fat component of the diet is only one factor affecting levels of blood lipids, but it is probably the main dietary factor.) Thus, it is possible to say that coronary disease is not merely a disease of ordinary people, but a disease of ordinary people who cannot tolerate ordinary ways of living and cannot adapt healthfully to the prevailing habits of our society. We know exceedingly little of what underlies this individual variation, either in terms of genetics or of environmental factors. Very little indeed is understood about it at the physiological level; this is a major neglected area for research.
TAKING STOCK We shall now discuss the 25 years of modern research into the etiology of coronary heart disease and the guidelines to prevention. I shall mention only some of the principal features. Two main sets of risk factors that predict future disease in the ordinary population have been identified.7' 8 Vol. 51, No. 1, January 1975
64
J. N. MORRIS
TABLE I. VIGOROUS EXERCISE (YE) IN LEISURE-TIME REPORTED BY MALE EXECUTIVE-GRADE CIVIL SERVANTS AGED 40 TO 65. SAMPLE FRIDAY AND SATURDAY 1968-1970 Form of VE
Examples
Active recreations*
Swimming
Keeping fit* Vigorous getting about*
Hill-climbing Dancing (spec.) Morning exercises Brisk walking
Heavy workt Gardening
"Do it yourself" Other
Climbing stairs
or
jogging
Running Cycling (spec.) Digging; felling trees; clearing brush Building in stone or concrete Moving heavy objects (spec.) Major (rusted) car repairs
450+ daily4
*Period of at least five minutes.
tPeriod of more than one half hour; or total of one hour or more in the two days. +Empirical observation. VE = vigorous exercise, involving an expenditure of at least 71/2 kilocals per minute.
Reproduced by permission from Morris, J. N., Adam, C., Chave, S. P. W., Sirey, C., Epstein, L., and Sheehan, D. J.: Vigorous exercise in leisure-time and the incidence of coronary heart disease. Lancet 1:333, 1973.
First, there is a set of behavior patterns. Overweight, smoking cigarettes, and inadequate exercise are the three main predictive factors that have been identified. I shall pause here to discuss exercise; it happens to be my own main research interest and it is another largely neglected area of research. Inadequate exercise as a risk factor. We became interested in exercise as a possible factor in coronary heart disease back in I949 when it was noticed that the conductors on London's buses had substantially fewer heart attacks and coronary deaths than the drivers of these vehicles.9' 10 These buses are double deckered: i.e., the conductor who takes the money and looks after the passengers has an active occupation and climbs many steps while the driver's is a typically sedentary job. Similar observations were made among other occupations which carried further into the morbid anatomy of the disease. In recent years, however, the social medicine unit of the Medical Research Council has lost interest in this kind of study. Importantly, if exercise is of value for health, in the future it will have to be the exercise that people take in their leisure time, because physical activity is steadily being eliminated from work. Even conservative projections of the year 2000 show almost the entire population deprived of any substantial physical effort in their work. Bull. N. Y. Acad. Med.
65
PRIMARY PREVENTION OF HEART ATTACK
TABLE II. PHYSICAL ACTIVITY IN LEISURE-TIME AND THE INCIDENCE CLINICAL ATTACKS) OF CORONARY HEART DISEASE (FIRST AMONG MALE BRITISH CIVIL SERVANTS AGED 40 TO 45 Vigorous exercise (VE)* Active recreation Keeping fit Vigorous getting about Heavy work Climbing 450+ stairs p.d. Men reporting VE (Expected)
First clinical attackst (238 mnen)
Matched controls (476 men)
5 3
19 16 21 78
1 19
0 25 (60)
8 120
*During the two days in 1968 to 1970; see Table I for definitions. to 1972. P
