Adv. Cardiol., vol. 18, pp. 196-207 (Karger, Basel 1976)
Physical Activity and Coronary Heart Disease in Populations from East and West Finland 1 S. PUNSAR and M. J. KARVONEN Finnish Heart Association, Research Programme, Helsinki
I. Introduction
There is some evidence from epidemiologic studies that physical exercise may reduce the incidence of coronary heart disease (CHD) and, particularly, the risk of dying from the disease [2, 11, 12, 14, 15]. However, data about the possible beneficial effect of vigorous physical activity at work are meager [14, 15]. In this paper, we present preliminary data of a IO-year follow-up of two cohorts of middle-aged men in which vigorous physical activity at work was not associated with a reduction in the risk of developing CHD.
II. Subjects and Methods
Supported by grants to M. J. KARVONEN from the US Public Health Service (NIH Grant No. HE-04754) and from the Finnish Academy.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
This study deals with ten years' experience of a cohort investigation of CHD which has now been conducted for 15 years on two rural male populations, one in the east, the other in the southwestern part of Finland. The initial examination of the populations, 1,711 men born between 1900 and 1919, was made in 1959. The two cohorts have since been followed up yearly for mortality data and examined at 5-year intervals, in 1964, 1969, and 1974. The response rate at each field examination has been about 95-98 %. The differences between the cohorts in risk factors for CHD and in other characteristics, as well as in the incidence of CHD, have been the subject of several papers [4,5,7,16]. In 10 years, the eastern cohort had experienced a death rate from CHD more than twice as high as the western cohort [16].
PuNSAR/KARVONEN
197
At the initial examination, an attempt was made to classify every subject into one of four categories of habitual physical activity; (1) sedentary and light; (2) moderate; (3) heavy; (4) vigorous physical activity. In most men, the grading was made by occupation; few men were engaged in leisure-time activities involving much extra physical activity. In category 1 were included, besides healthy sedentary men, also invalids and bed-ridden subjects. Category 2 included men with an occupation involving more physical activity than just sitting or standing (truck drivers, carpenters, foremen, shopkeepers, etc.). Category 3 included farmers, in addition to men with other occupations involving relatively heavy physical activity. Category 4 included full-time or part-time lumberjacks, i.e. men using vigorous activity at work (in 1959 lumbering was an important occupation in Finland, particularly in the eastern part of the country). For analyses published elsewhere [4,5], categories 3 and 4 were combined; for the present purpose, the two were kept separate. In this paper, we deal with 10 years' observations in the four categories formed at the start of the follow-up. Related base-line observations have been reported previously [7]. The methods employed in obtaining clinical and other data have been described elsewhere [9,10]. In classifying the men for chest pain symptoms and for the cause of death, only slight modifications were made to the criteria previously employed. Electrocardiograms (ECG) were coded by the 'Minnesota code' [1], the 'old' code, and classified as described in the following results. The study included only subjects whose data at entry were complete as regards information on physical activity, chest pain symptoms, and resting electrocardiograms. Thus, the study comprises data on 1,648 men altogether.
III. Results
Prevalence findings at entry in relation to physical activity. As described previously [5, 16], the eastern cohort showed a high prevalence of angina
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
In 1959, at entry into the study, most of these rural men, then aged 40- 59, were engaged in active jobs. Roughly 10% of both populations were classified into the sedentary category (category 1) which also included sick men. The major portion of the men were engaged in heavy, or vigorous, work activity. Figures 1 and 2 show the distribution in 1959 of the men of the two cohorts into the four categories of habitual physical activity and the age distribution among the categories. In the western area (fig. 1), the age distribution of the men in categories 1-3 was roughly similar; however, lumberjacks (category 4) tended to be slightly younger. Of the eastern cohort (fig. 2), a higher proportion were lumberjacks, and the age difference was more marked. The tendency towards younger age of the lumberjacks is relevant in evaluating the results of this preliminary analysis on the relation of habitual physical activity to CHD.
198
PUNSAR/KARVONEN No. of
mon
Toul
N
7.
115
593
53
2
3
4
150
lOa
50
Age cl ...
1
2 3 4
ACT.
Fig. 1. Physical activity. west Finland. Men classed by age and habitual physical activity at entry. ACT. 1 = Sedentary and light; ACT. 2 = moderate; ACT. 3 = heavy; ACT. 4 = vigorous (lumberjacks). Age classes: 1 = 40-44; 2 = 45-49; 3 = 50-54; 4 = 55-59. No of
Total N
96
146
197
374
2
3
4
150
lOa
50
Ag. class 1 2 3 4
ACT.
pectoris and a high mortality from CHD. Tables I and II present the prevalence of chest pain symptoms and resting ECG abnormalities at the entry examination in relation to habitual physical activity. for the two populations. As expected, category 1, which also included the sick men, showed the highest proportion with chest pain symptoms (with or without ECG abnormalities). In both populations the symptoms decreased with higher levels of physical activity.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Fig. 2. Physical activity. east Finland. Men classed by age and habitual physical activity at entry. For explanation. see figure 1.
Physical Activity and CHD in a Population
199
Table I. Chest pain symptoms and resting ECG abnormalities 1 at entry in relation to physical activity2. Age classes combined. West Finland Category
Total number of men AP or attack, % ECG abnormalities only, %
2
2
3
4
74 5.4 13.5
115 4.3 8.7
593 1.3 5.4
53
0 13.2
1 Minnesota code: Q wave ('old' code I: 1-3); A-V blocks (VI: 1,2,4); RBBB; LBBB; IVB; rhythm disturbances (VIII: 0,1-6,9). 2 For explanation, see figure 1.
Table II. Chest pain symptoms and resting ECG abnormalities 1 at entry in relation to physical activity2. Age classes combined. East Finland Category
Total number of men AP or attack, % ECG abnormalities only, %
2
2
96 11.5
146
4.2
10.3 3.4
3
4
197 8.6 4.6
374 4.8 5.9
Abnormalities in resting EeG only (without chest pain symptoms) were more common in the western population, a finding reported previously [16]. In the west, the lowest frequency was found in category 3 (farmers), while lumberjacks (category 4) showed a high frequency of EeG abnormalities. In the east, EeG abnormalities were rather evenly distributed among the four categories. At entry in 1959, almost all men were subjected to an exercise test. Table III shows the percentages of ischemic ST depression in men who were symptomless and who did not in their resting EeG show the abnormalities presented in tables I and II. As could be expected, post-exercise ST depression was not particularly common among these men. In both populations, the activity category 1 showed the highest frequency of post-exercise ST depression, but there were no great differences among the other categories.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
1 For explanation, see table I. 2 For explanation, see figure 1.
200
PUNSAR/KARVONEN
Table III. Occurrence of post-exercise ST depression! at entry in relation to physical activity 2. Men with no chest pain symptoms and no resting ECG abnormalities 3 • Age classes combined Category 2
2
3
4
West Finland Total number of men ST depression post-exercise, %
52 9.6
98 2.0
545 2.4
46 0
East Finland Total number of men ST depression post-exercise, %
70 4.9
119 3.4
165 1.2
331 1.5
1 Horizontal or downward sloping ST segment depression of 0.5 mm or more. 2 For explanation, see figure 1. 3 For explanation, see table I.
~ Tou' mon.n,y Coronary
% 80
Man at risk" N 1. 15
% .0
80
15
20
26
40
2
3
4
50
.0
30
20
10
2
3
WEST
4
EAST
Fig. 3. 10-year mortality of men with chest pain symptoms and/or resting ECG abnormalities at entry (tables I and II). Relation to physical activity at entry. Ages combined. For other explanation, see figure 1.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
ACT.
Physical Activity and CHD in a Population
% 25
Men .t flsk J
47
96
201
%
N
532
46
25
67
115
163
326
2
3
4
20
20
15
10
ACT.
2 WEST
3
4
EAST
Fig. 4. 10-year mortality of men initially free of CHD. Relation to physical activity at entry. Ages combined. Men initially free of CHD: no chest pain symptoms at entry; no resting and post-exercise ECG abnormalities (tables I and III). For other explanation, see figure 1.
The ECG abnormalities reported here (footnotes, tables I and III) do not all, of course, result from CHD: our main objective was to study the relation of physical activity to CHD in a cohort initially free of the disease, and the abnormalities in resting and post-exercise ECG were used to exclude from the cohort men with definite and possible CHD at entry.
Mortality of men initially free of CHD. The IO-year mortality of men without symptoms and ECG signs of CHD at entry showed quite a different relation to habitual physical activity. Figure 4 shows that in both popula-
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Mortality of men with chest pain symptoms or resting ECG abnormalities at entry. The four categories of habitual physical activity were examined for deaths in 10 years; separately for men who had had symptoms and/or abnormalities in their resting ECG at the entry examination, and for those without symptoms and with a normal resting and post-exercise ECG. For the present purpose, men with chest pain or resting ECG abnormalities only were combined into one group. It is seen from figure 3 that, in general, the overall mortality of this group was higher in the east than in the west and that it decreased in both populations with increasing level of work activity. In the east, the mortality from CHD seemed to parallel the total mortality and was lowest among the lumberjacks.
202
PUNSAR!KARVONEN No .
Sudden Oellyed
of
duths 10
DTot'l
OJ CHD·fr• • • t
entry
Fig. 5. Deaths from CHD classified according to interval between onset of symptoms and death (west Finland). Relation to physical activity at entry. Total number of deaths and number in men initially free of CHD (fig. 4). Ages combined. Sudden = 1 h or less; delayed = more than 1 h. In parentheses, number of deaths with unspecified interval. For other explanation, see figure 1. No. of de.th.
15
10
tions, but more clearly in the eastern one, the overall mortality decreased from category 1 to 3 and increased again in category 4 (lumberjacks). The mortality from CHD was higher in the east, but in neither area did it show a systematic trend with the activity of work. Lumberjacks showed, if anything, an equal, or higher, mortality from CHD than farmers (category 3).
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Fig. 6. Deaths from CHD classified according to interval between onset of symptoms and death (east Finland). Relation to physical activity at entry. Total number of deaths and number in men initially free of CHD (fig. 4). Ages combined. For other explanation, see figures 1 and 5.
Physical Activity and CHD in a Population
203
Table IV. Chest pain symptoms and ECG abnormalities (resting or post-exercise!) at the 10-year reexamination among survivors initially free of CHD2. Relation to physical activity at entry3. Ages combined. West Finland Category at entry
Total number of survivors free of CHD at entry 10-years findings AP or attack, % ECG abnormalities only, % Not examined, %
2
2
3
4
41
84
469
39
14.6 12.2 2.4
17.9 13.1 1.2
10.7 7.7 1.9
17.9 5.1 2.6
1 ECG abnormalities: Minnesota code; Q wave ('old' code I: 1-3); A-V blocks (VI: 1, 2, 4); RBBB; LBBB; IVB; atrial fibrillation; horizontal or downward sloping ST segment depression of 0.5 mm or more (resting or post-exercise ECG). 2 For explanation, see figure 4. 3 For explanation, see figure 1.
Prevalence of CHD at the IO-year reexamination in men initially free of CHD. The findings at the 10-year reexamination are here shown only for men who were regarded at the initial examination to be free of definite or possible CRD. Tables IV and V show the percentages of men who had during the 10 years developed symptoms of chest pain or BCG abnormalities (resting or post-exercise BCG) without chest pain. In the west, the lowest percentage of chest pain symptoms was found in category 3; in the east, the lowest percentage was found among men who were least active. In both areas
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Physical activity and sudden death. Deaths from CRD were classified according to the length of the terminal episode. For the present analysis, sudden death was defined as death occurring within I h from the onset of terminal symptoms, delayed death as following a known longer interval, and other coronary death as 'unspecified'. As seen from figures 5 and 6, there was no association between the level of physical activity as assessed at the entry examination, and the suddenness of the deaths (because of small numbers, the deaths in categories 1 and 2 have been combined), whether analyzed in all deaths from CRD, or only in the groups of men who were initially free ofCRD.
204
PUNSAR/KARVONEN
Table V. Chest pain symptoms and ECG abnormalities (resting or post-exercise 1) at the 10-year reexamination among survivors initially free of CHD2. Relation to physical activity at entry3. Ages combined. East Finland Category at entry
Total number of survivors free of CHD at entry lO-year findings AP or attack, % ECG abnormalities only, % Not examined, %
2
2
3
4
52
98
147
283
5.8 3.8 3.8
23.5 5.1 3.1
22.4 7.5 1.4
27.2 5.6 1.8
1 For explanation, see table IV. 2 For explanation, see figure 4. 3 For explanation, see figure 1.
lumberjacks (category 4) showed, if anything, a higher prevalence of chest pain than the other men. The ECG abnormalities as sole manifestation of CHD decreased in the west with increasing level of physical activity. In the east, however, no such trend was present. It will be noticed when the percentages of the two indicators of CHD are combined that in both areas lumberjacks showed a higher total percentage of CHD than men with less heavy occupations (category 3).
Our data from the entry examination suffer from the usual limitations of prevalence data. Obviously, the sedentary class (category 1) was unduly loaded with men having CHD, and selection bias may have played a role in other categories too. Also, the differences observed in the 10-year mortality of men who at the entry examination had symptoms or signs of CHD may not necessarily be related to differences in physical activity. Among the subjects labeled as cases with CHD, chest pain was relatively more common among the lighter activity categories and ECG abnormalities only among the heavier ones.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
IV. Discussion
205
More emphasis can, perhaps, be put on the 10-year experience of men who were regarded as being initially free of CHD. Among these men, the mortality from all causes was lowest among farmers and other men engaged in a relatively heavy occupation (activity class 3) while lumberjacks, engaged in vigorous physical activity (category 4), showed a somewhat higher total mortality. On the other hand, the mortality from CHD did not have a definite association with the level of habitual physical activity. Also, the relative number of sudden deaths in men free of CHD at entry did not vary with work activity. Neither did the development of CHD in 10 years among the survivors who were regarded as initially free of the disease indicate a clear-cut protective effect of heavy or, particularly, of vigorous physical activity. In the west, chest pain symptoms showed the lowest incidence in category 3 (farmers), while in the east, the lowest incidence was found in tne least active men. In both areas, lumberjacks had, if anything, a higher incidence of chest pain symptoms and, when BCG abnormalities are included, a higher total percentage of CHD than men with a less heavy occupation (category 3). It is of special interest in this study that initially healthy lumberjacks, i. e. men who were free of CHD and engaged in extremely heavy work activity, fared no better but rather worse as regards the development of CHD than men with a less heavy (category 3) occupation. Job transfers in the two cohorts were rare and were mainly caused by declining health. As each individual was classified according to his 1959 occupation, the effect of subsequent selective removal on differences between the categories is obviously eliminated. Nor can the experience in lumberjacks be explained by important differences in classic risk factors of CHD. Our previous study [7] on the eastern cohort showed that lumberjacks did not differ in their level of blood pressure from other men in the same local area and, although lumberjacks consume more calories and fats [6], they were leaner [3] and had the same average serum cholesterol as the other men (267.2 vs. 265.5 mg%). However, the lumberjacks tended to smoke slightly more [7]. On the other hand, the mean age of lumberjacks was slightly lower, and any selection bias would have favored the inclusion of particularly healthy men in this occupation. Our preliminary experience on lumberjacks is at variance with the suggestions from two large population studies where vigorous physical activity was reported to have a beneficial effect on the incidence of CHD [12, 14, 15]. MORRIS et al. [12] found in their study on civil servants that vigorous leisure time exercise was associated with a reduced incidence of fatal and nonfatal cardiac attacks, and PAFFENBARGER et al. [14, 15] showed that longshoremen
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Physical Activity and CHD in a Population
PUNSAR/KARVONEN
206
with heavy work activity, requiring on average 1,876 kcal over basal output per 8-hour work day, had a lower death rate from CHD and, particularly, fewer sudden deaths than their counterparts with a less heavy work activity. While there are several explanations for the divergent findings in our lumberjacks, the following comments seem particularly pertinent. The work of lumberjacks is known to require more energy than any other occupation, including that of longshoreman. Recorded energy expenditure figures range from 4,500 to 8,000 kcal per day [6, 8]. If extreme physical activity of work favorably affects the development of CHD, then evidence for such an effect should be found among the lumberjacks. However, this effect might be obscured and the present results biased, if lumberjacks had some overriding risk factors making them particularly susceptible to CHD. Apart from the differences listed above, lumberjacks stand lower socioeconomically than men with other occupations, and retire through disability at an earlier age [13]. Whether these characteristics oflumberjacks are related to their susceptibility to CHD can only be guessed at. Moreover, there might be some unknown factors promoting the development of CHD in lumberjacks. Whatever such factors might be, the present results indicate that the vigorous work activity of lumberjacks cannot counteract the effect of such factors. Another explanation, of course, would be that vigorous habitual physical activity which exceeds a certain threshold is deleterious or, at least, does not further reduce the risk of CHD. Whether this is true or not will be the object of our further analyses of the two cohorts, which will also include the results of the I5-year follow-up.
2
2
3 4
5
BLACKBURN, H.; KEyS, A.; SIMONSON, E.; RAUTAHARJU, P. M., and PUNSAR, S.: The electrocardiogram in population studies. A classification system. Circulation 21: 1160-1175 (1960). CASSEL, J.; HEYDEN, S.; BARTEL, A. G.; KAPLAN, B. H.; TYROLER, H. A.; CORNONI, J. C., and HAMES, C. G.: Occupation and physical activity and coronary heart disease. Archs intern. Med. 128: 920-928 (1971). KARVONEN, M. J.: Health problems of lumberjacks. Ergonomics 5: 179-180 (1962). KARVONEN, M. J.; BLOMQVJST, G.; KALLIO, Y.; ORMA, E.; PUNSAR, S.; RAUTAHARHW, P.; TAKKUNEN, J., and KEyS, A.: Men in rural East and West Finland, pp. 169-190; in KEYS et al. Epidemiological studies related to coronary heart disease: characteristics of men aged 40-59 in seven countries. Acta med. scand. 460 : suppl. (1967). KARVONEN, M. J.; ORMA, E.; PUNSAR, S.; KALLIO, Y.; ARSTILA, M.; LUOMANMAKI,
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
References
Physical Activity and CHD in a Population
7
8 9
10 11
12
13
14
15 16
K., and TAKKUNEN, J.: Five-year experience in Finland, pp. 52-62; in KEyS Coronary heart disease in seven countries. Am. Heart Ass. Monogr. 29 (1970). KARVONEN, M. J.; PEKKARINEN, M.; METSALA, P., and RAUTANEN, Y.: Diet and serum cholesterol of lumberjacks. Br. J. Nutr. 15: 157-164 (1961). KARVONEN, M. J.; RAUTAHARJU, P. M.; ORMA, E.; PUNSAR, S., and TAKKUNEN, J.: Heart disease and employment. Cardiovascular studies on lumberjacks. J.Oceup. Med. 3: 49-53 (1961). KARVONEN, M. J. and TURPEINEN, 0.: Consumption and selection of food in competitive lumber work. J. appl. Physiol. 6: 603-610 (1954). KEyS, A.; ARAVANIS, c.; BLACKBURN, H. W.; BUCHEM, F. S. P. VAN; BUZINA, R.; DJORDJEVIC, B. S.; DONTAS, A. S.; FIDANZA, F.; KARVONEN, M. J.; KIMuRA, N . ; LEKos, D.; MONTI, M.; PUDDU, V., and TAYLOR, H. L.: Epidemiological studies related to coronary heart disease: characteristics of men aged 40-59 in seven countries. Acta med. scand. Suppl 460 (1967). KEYS, A. (ed.): Coronary heart disease in seven countries. Am. Heart Ass. Monogr. 29 (1970). MORRIS, J. N.; KAGAN, A.; PATTISON, D. C.; GARDNER, M. J., and RAFFLE, P. A. B.: Incidence and prediction of ischaemic heart disease in London busmen. Lancet ii: 553-559 (1966). MORRIS, J. N.; CRAVE, S. P. W.; ADAM, C.; SIREY, c.; EpSTEIN, L., and SHEEHAN, D. J.: Vigorous exercise in leisure-time and the incidence of coronary heart disease. Lancet i: 333-339 (1973). NYGARD, K.: Subjective, medical, and social disability. Reports Inst. Oce. Health (in Finnish); Helsinki (1970). PAFFENBARGER, R. S.,jr.; LAUGHLIN, M. E.; GIMA, A. S., and BLACK, R. A.: Work activity of longshoremen as related to death from coronary heart disease and stroke. New Engl. J. Med. 282: 1109-1114 (1970). PAFFENBARGER, R. S., jr. and HALE, W. E. : Work activity and coronary heart mortality. New Eng!. J. Med. 292: 545-550 (1975). PUNSAR, S. and KARVONEN, M. J.: Angina pectoris and ECG abnormalities in relation to prognosis of coronary heart disease in population studies in Finland; in HALONEN and LOUHIJA Early diagnosis of coronary heart disease. Adv. Cardio!., vo!. 8, pp. 148-161 (Karger, Basel 1973).
Dr. S. PUNSAR, Finnish Heart Association, Research Programme, Koroistentie 6 f, SF-00280 Helsinki 28 (Finland)
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
6
207
Physical Activity and Coronary Heart Disease in Populations from East and West Finland 1 S. PUNSAR and M. J. KARVONEN Finnish Heart Association, Research Programme, Helsinki
I. Introduction
There is some evidence from epidemiologic studies that physical exercise may reduce the incidence of coronary heart disease (CHD) and, particularly, the risk of dying from the disease [2, 11, 12, 14, 15]. However, data about the possible beneficial effect of vigorous physical activity at work are meager [14, 15]. In this paper, we present preliminary data of a IO-year follow-up of two cohorts of middle-aged men in which vigorous physical activity at work was not associated with a reduction in the risk of developing CHD.
II. Subjects and Methods
Supported by grants to M. J. KARVONEN from the US Public Health Service (NIH Grant No. HE-04754) and from the Finnish Academy.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
This study deals with ten years' experience of a cohort investigation of CHD which has now been conducted for 15 years on two rural male populations, one in the east, the other in the southwestern part of Finland. The initial examination of the populations, 1,711 men born between 1900 and 1919, was made in 1959. The two cohorts have since been followed up yearly for mortality data and examined at 5-year intervals, in 1964, 1969, and 1974. The response rate at each field examination has been about 95-98 %. The differences between the cohorts in risk factors for CHD and in other characteristics, as well as in the incidence of CHD, have been the subject of several papers [4,5,7,16]. In 10 years, the eastern cohort had experienced a death rate from CHD more than twice as high as the western cohort [16].
PuNSAR/KARVONEN
197
At the initial examination, an attempt was made to classify every subject into one of four categories of habitual physical activity; (1) sedentary and light; (2) moderate; (3) heavy; (4) vigorous physical activity. In most men, the grading was made by occupation; few men were engaged in leisure-time activities involving much extra physical activity. In category 1 were included, besides healthy sedentary men, also invalids and bed-ridden subjects. Category 2 included men with an occupation involving more physical activity than just sitting or standing (truck drivers, carpenters, foremen, shopkeepers, etc.). Category 3 included farmers, in addition to men with other occupations involving relatively heavy physical activity. Category 4 included full-time or part-time lumberjacks, i.e. men using vigorous activity at work (in 1959 lumbering was an important occupation in Finland, particularly in the eastern part of the country). For analyses published elsewhere [4,5], categories 3 and 4 were combined; for the present purpose, the two were kept separate. In this paper, we deal with 10 years' observations in the four categories formed at the start of the follow-up. Related base-line observations have been reported previously [7]. The methods employed in obtaining clinical and other data have been described elsewhere [9,10]. In classifying the men for chest pain symptoms and for the cause of death, only slight modifications were made to the criteria previously employed. Electrocardiograms (ECG) were coded by the 'Minnesota code' [1], the 'old' code, and classified as described in the following results. The study included only subjects whose data at entry were complete as regards information on physical activity, chest pain symptoms, and resting electrocardiograms. Thus, the study comprises data on 1,648 men altogether.
III. Results
Prevalence findings at entry in relation to physical activity. As described previously [5, 16], the eastern cohort showed a high prevalence of angina
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
In 1959, at entry into the study, most of these rural men, then aged 40- 59, were engaged in active jobs. Roughly 10% of both populations were classified into the sedentary category (category 1) which also included sick men. The major portion of the men were engaged in heavy, or vigorous, work activity. Figures 1 and 2 show the distribution in 1959 of the men of the two cohorts into the four categories of habitual physical activity and the age distribution among the categories. In the western area (fig. 1), the age distribution of the men in categories 1-3 was roughly similar; however, lumberjacks (category 4) tended to be slightly younger. Of the eastern cohort (fig. 2), a higher proportion were lumberjacks, and the age difference was more marked. The tendency towards younger age of the lumberjacks is relevant in evaluating the results of this preliminary analysis on the relation of habitual physical activity to CHD.
198
PUNSAR/KARVONEN No. of
mon
Toul
N
7.
115
593
53
2
3
4
150
lOa
50
Age cl ...
1
2 3 4
ACT.
Fig. 1. Physical activity. west Finland. Men classed by age and habitual physical activity at entry. ACT. 1 = Sedentary and light; ACT. 2 = moderate; ACT. 3 = heavy; ACT. 4 = vigorous (lumberjacks). Age classes: 1 = 40-44; 2 = 45-49; 3 = 50-54; 4 = 55-59. No of
Total N
96
146
197
374
2
3
4
150
lOa
50
Ag. class 1 2 3 4
ACT.
pectoris and a high mortality from CHD. Tables I and II present the prevalence of chest pain symptoms and resting ECG abnormalities at the entry examination in relation to habitual physical activity. for the two populations. As expected, category 1, which also included the sick men, showed the highest proportion with chest pain symptoms (with or without ECG abnormalities). In both populations the symptoms decreased with higher levels of physical activity.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Fig. 2. Physical activity. east Finland. Men classed by age and habitual physical activity at entry. For explanation. see figure 1.
Physical Activity and CHD in a Population
199
Table I. Chest pain symptoms and resting ECG abnormalities 1 at entry in relation to physical activity2. Age classes combined. West Finland Category
Total number of men AP or attack, % ECG abnormalities only, %
2
2
3
4
74 5.4 13.5
115 4.3 8.7
593 1.3 5.4
53
0 13.2
1 Minnesota code: Q wave ('old' code I: 1-3); A-V blocks (VI: 1,2,4); RBBB; LBBB; IVB; rhythm disturbances (VIII: 0,1-6,9). 2 For explanation, see figure 1.
Table II. Chest pain symptoms and resting ECG abnormalities 1 at entry in relation to physical activity2. Age classes combined. East Finland Category
Total number of men AP or attack, % ECG abnormalities only, %
2
2
96 11.5
146
4.2
10.3 3.4
3
4
197 8.6 4.6
374 4.8 5.9
Abnormalities in resting EeG only (without chest pain symptoms) were more common in the western population, a finding reported previously [16]. In the west, the lowest frequency was found in category 3 (farmers), while lumberjacks (category 4) showed a high frequency of EeG abnormalities. In the east, EeG abnormalities were rather evenly distributed among the four categories. At entry in 1959, almost all men were subjected to an exercise test. Table III shows the percentages of ischemic ST depression in men who were symptomless and who did not in their resting EeG show the abnormalities presented in tables I and II. As could be expected, post-exercise ST depression was not particularly common among these men. In both populations, the activity category 1 showed the highest frequency of post-exercise ST depression, but there were no great differences among the other categories.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
1 For explanation, see table I. 2 For explanation, see figure 1.
200
PUNSAR/KARVONEN
Table III. Occurrence of post-exercise ST depression! at entry in relation to physical activity 2. Men with no chest pain symptoms and no resting ECG abnormalities 3 • Age classes combined Category 2
2
3
4
West Finland Total number of men ST depression post-exercise, %
52 9.6
98 2.0
545 2.4
46 0
East Finland Total number of men ST depression post-exercise, %
70 4.9
119 3.4
165 1.2
331 1.5
1 Horizontal or downward sloping ST segment depression of 0.5 mm or more. 2 For explanation, see figure 1. 3 For explanation, see table I.
~ Tou' mon.n,y Coronary
% 80
Man at risk" N 1. 15
% .0
80
15
20
26
40
2
3
4
50
.0
30
20
10
2
3
WEST
4
EAST
Fig. 3. 10-year mortality of men with chest pain symptoms and/or resting ECG abnormalities at entry (tables I and II). Relation to physical activity at entry. Ages combined. For other explanation, see figure 1.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
ACT.
Physical Activity and CHD in a Population
% 25
Men .t flsk J
47
96
201
%
N
532
46
25
67
115
163
326
2
3
4
20
20
15
10
ACT.
2 WEST
3
4
EAST
Fig. 4. 10-year mortality of men initially free of CHD. Relation to physical activity at entry. Ages combined. Men initially free of CHD: no chest pain symptoms at entry; no resting and post-exercise ECG abnormalities (tables I and III). For other explanation, see figure 1.
The ECG abnormalities reported here (footnotes, tables I and III) do not all, of course, result from CHD: our main objective was to study the relation of physical activity to CHD in a cohort initially free of the disease, and the abnormalities in resting and post-exercise ECG were used to exclude from the cohort men with definite and possible CHD at entry.
Mortality of men initially free of CHD. The IO-year mortality of men without symptoms and ECG signs of CHD at entry showed quite a different relation to habitual physical activity. Figure 4 shows that in both popula-
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Mortality of men with chest pain symptoms or resting ECG abnormalities at entry. The four categories of habitual physical activity were examined for deaths in 10 years; separately for men who had had symptoms and/or abnormalities in their resting ECG at the entry examination, and for those without symptoms and with a normal resting and post-exercise ECG. For the present purpose, men with chest pain or resting ECG abnormalities only were combined into one group. It is seen from figure 3 that, in general, the overall mortality of this group was higher in the east than in the west and that it decreased in both populations with increasing level of work activity. In the east, the mortality from CHD seemed to parallel the total mortality and was lowest among the lumberjacks.
202
PUNSAR!KARVONEN No .
Sudden Oellyed
of
duths 10
DTot'l
OJ CHD·fr• • • t
entry
Fig. 5. Deaths from CHD classified according to interval between onset of symptoms and death (west Finland). Relation to physical activity at entry. Total number of deaths and number in men initially free of CHD (fig. 4). Ages combined. Sudden = 1 h or less; delayed = more than 1 h. In parentheses, number of deaths with unspecified interval. For other explanation, see figure 1. No. of de.th.
15
10
tions, but more clearly in the eastern one, the overall mortality decreased from category 1 to 3 and increased again in category 4 (lumberjacks). The mortality from CHD was higher in the east, but in neither area did it show a systematic trend with the activity of work. Lumberjacks showed, if anything, an equal, or higher, mortality from CHD than farmers (category 3).
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Fig. 6. Deaths from CHD classified according to interval between onset of symptoms and death (east Finland). Relation to physical activity at entry. Total number of deaths and number in men initially free of CHD (fig. 4). Ages combined. For other explanation, see figures 1 and 5.
Physical Activity and CHD in a Population
203
Table IV. Chest pain symptoms and ECG abnormalities (resting or post-exercise!) at the 10-year reexamination among survivors initially free of CHD2. Relation to physical activity at entry3. Ages combined. West Finland Category at entry
Total number of survivors free of CHD at entry 10-years findings AP or attack, % ECG abnormalities only, % Not examined, %
2
2
3
4
41
84
469
39
14.6 12.2 2.4
17.9 13.1 1.2
10.7 7.7 1.9
17.9 5.1 2.6
1 ECG abnormalities: Minnesota code; Q wave ('old' code I: 1-3); A-V blocks (VI: 1, 2, 4); RBBB; LBBB; IVB; atrial fibrillation; horizontal or downward sloping ST segment depression of 0.5 mm or more (resting or post-exercise ECG). 2 For explanation, see figure 4. 3 For explanation, see figure 1.
Prevalence of CHD at the IO-year reexamination in men initially free of CHD. The findings at the 10-year reexamination are here shown only for men who were regarded at the initial examination to be free of definite or possible CRD. Tables IV and V show the percentages of men who had during the 10 years developed symptoms of chest pain or BCG abnormalities (resting or post-exercise BCG) without chest pain. In the west, the lowest percentage of chest pain symptoms was found in category 3; in the east, the lowest percentage was found among men who were least active. In both areas
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Physical activity and sudden death. Deaths from CRD were classified according to the length of the terminal episode. For the present analysis, sudden death was defined as death occurring within I h from the onset of terminal symptoms, delayed death as following a known longer interval, and other coronary death as 'unspecified'. As seen from figures 5 and 6, there was no association between the level of physical activity as assessed at the entry examination, and the suddenness of the deaths (because of small numbers, the deaths in categories 1 and 2 have been combined), whether analyzed in all deaths from CRD, or only in the groups of men who were initially free ofCRD.
204
PUNSAR/KARVONEN
Table V. Chest pain symptoms and ECG abnormalities (resting or post-exercise 1) at the 10-year reexamination among survivors initially free of CHD2. Relation to physical activity at entry3. Ages combined. East Finland Category at entry
Total number of survivors free of CHD at entry lO-year findings AP or attack, % ECG abnormalities only, % Not examined, %
2
2
3
4
52
98
147
283
5.8 3.8 3.8
23.5 5.1 3.1
22.4 7.5 1.4
27.2 5.6 1.8
1 For explanation, see table IV. 2 For explanation, see figure 4. 3 For explanation, see figure 1.
lumberjacks (category 4) showed, if anything, a higher prevalence of chest pain than the other men. The ECG abnormalities as sole manifestation of CHD decreased in the west with increasing level of physical activity. In the east, however, no such trend was present. It will be noticed when the percentages of the two indicators of CHD are combined that in both areas lumberjacks showed a higher total percentage of CHD than men with less heavy occupations (category 3).
Our data from the entry examination suffer from the usual limitations of prevalence data. Obviously, the sedentary class (category 1) was unduly loaded with men having CHD, and selection bias may have played a role in other categories too. Also, the differences observed in the 10-year mortality of men who at the entry examination had symptoms or signs of CHD may not necessarily be related to differences in physical activity. Among the subjects labeled as cases with CHD, chest pain was relatively more common among the lighter activity categories and ECG abnormalities only among the heavier ones.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
IV. Discussion
205
More emphasis can, perhaps, be put on the 10-year experience of men who were regarded as being initially free of CHD. Among these men, the mortality from all causes was lowest among farmers and other men engaged in a relatively heavy occupation (activity class 3) while lumberjacks, engaged in vigorous physical activity (category 4), showed a somewhat higher total mortality. On the other hand, the mortality from CHD did not have a definite association with the level of habitual physical activity. Also, the relative number of sudden deaths in men free of CHD at entry did not vary with work activity. Neither did the development of CHD in 10 years among the survivors who were regarded as initially free of the disease indicate a clear-cut protective effect of heavy or, particularly, of vigorous physical activity. In the west, chest pain symptoms showed the lowest incidence in category 3 (farmers), while in the east, the lowest incidence was found in tne least active men. In both areas, lumberjacks had, if anything, a higher incidence of chest pain symptoms and, when BCG abnormalities are included, a higher total percentage of CHD than men with a less heavy occupation (category 3). It is of special interest in this study that initially healthy lumberjacks, i. e. men who were free of CHD and engaged in extremely heavy work activity, fared no better but rather worse as regards the development of CHD than men with a less heavy (category 3) occupation. Job transfers in the two cohorts were rare and were mainly caused by declining health. As each individual was classified according to his 1959 occupation, the effect of subsequent selective removal on differences between the categories is obviously eliminated. Nor can the experience in lumberjacks be explained by important differences in classic risk factors of CHD. Our previous study [7] on the eastern cohort showed that lumberjacks did not differ in their level of blood pressure from other men in the same local area and, although lumberjacks consume more calories and fats [6], they were leaner [3] and had the same average serum cholesterol as the other men (267.2 vs. 265.5 mg%). However, the lumberjacks tended to smoke slightly more [7]. On the other hand, the mean age of lumberjacks was slightly lower, and any selection bias would have favored the inclusion of particularly healthy men in this occupation. Our preliminary experience on lumberjacks is at variance with the suggestions from two large population studies where vigorous physical activity was reported to have a beneficial effect on the incidence of CHD [12, 14, 15]. MORRIS et al. [12] found in their study on civil servants that vigorous leisure time exercise was associated with a reduced incidence of fatal and nonfatal cardiac attacks, and PAFFENBARGER et al. [14, 15] showed that longshoremen
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
Physical Activity and CHD in a Population
PUNSAR/KARVONEN
206
with heavy work activity, requiring on average 1,876 kcal over basal output per 8-hour work day, had a lower death rate from CHD and, particularly, fewer sudden deaths than their counterparts with a less heavy work activity. While there are several explanations for the divergent findings in our lumberjacks, the following comments seem particularly pertinent. The work of lumberjacks is known to require more energy than any other occupation, including that of longshoreman. Recorded energy expenditure figures range from 4,500 to 8,000 kcal per day [6, 8]. If extreme physical activity of work favorably affects the development of CHD, then evidence for such an effect should be found among the lumberjacks. However, this effect might be obscured and the present results biased, if lumberjacks had some overriding risk factors making them particularly susceptible to CHD. Apart from the differences listed above, lumberjacks stand lower socioeconomically than men with other occupations, and retire through disability at an earlier age [13]. Whether these characteristics oflumberjacks are related to their susceptibility to CHD can only be guessed at. Moreover, there might be some unknown factors promoting the development of CHD in lumberjacks. Whatever such factors might be, the present results indicate that the vigorous work activity of lumberjacks cannot counteract the effect of such factors. Another explanation, of course, would be that vigorous habitual physical activity which exceeds a certain threshold is deleterious or, at least, does not further reduce the risk of CHD. Whether this is true or not will be the object of our further analyses of the two cohorts, which will also include the results of the I5-year follow-up.
2
2
3 4
5
BLACKBURN, H.; KEyS, A.; SIMONSON, E.; RAUTAHARJU, P. M., and PUNSAR, S.: The electrocardiogram in population studies. A classification system. Circulation 21: 1160-1175 (1960). CASSEL, J.; HEYDEN, S.; BARTEL, A. G.; KAPLAN, B. H.; TYROLER, H. A.; CORNONI, J. C., and HAMES, C. G.: Occupation and physical activity and coronary heart disease. Archs intern. Med. 128: 920-928 (1971). KARVONEN, M. J.: Health problems of lumberjacks. Ergonomics 5: 179-180 (1962). KARVONEN, M. J.; BLOMQVJST, G.; KALLIO, Y.; ORMA, E.; PUNSAR, S.; RAUTAHARHW, P.; TAKKUNEN, J., and KEyS, A.: Men in rural East and West Finland, pp. 169-190; in KEYS et al. Epidemiological studies related to coronary heart disease: characteristics of men aged 40-59 in seven countries. Acta med. scand. 460 : suppl. (1967). KARVONEN, M. J.; ORMA, E.; PUNSAR, S.; KALLIO, Y.; ARSTILA, M.; LUOMANMAKI,
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
References
Physical Activity and CHD in a Population
7
8 9
10 11
12
13
14
15 16
K., and TAKKUNEN, J.: Five-year experience in Finland, pp. 52-62; in KEyS Coronary heart disease in seven countries. Am. Heart Ass. Monogr. 29 (1970). KARVONEN, M. J.; PEKKARINEN, M.; METSALA, P., and RAUTANEN, Y.: Diet and serum cholesterol of lumberjacks. Br. J. Nutr. 15: 157-164 (1961). KARVONEN, M. J.; RAUTAHARJU, P. M.; ORMA, E.; PUNSAR, S., and TAKKUNEN, J.: Heart disease and employment. Cardiovascular studies on lumberjacks. J.Oceup. Med. 3: 49-53 (1961). KARVONEN, M. J. and TURPEINEN, 0.: Consumption and selection of food in competitive lumber work. J. appl. Physiol. 6: 603-610 (1954). KEyS, A.; ARAVANIS, c.; BLACKBURN, H. W.; BUCHEM, F. S. P. VAN; BUZINA, R.; DJORDJEVIC, B. S.; DONTAS, A. S.; FIDANZA, F.; KARVONEN, M. J.; KIMuRA, N . ; LEKos, D.; MONTI, M.; PUDDU, V., and TAYLOR, H. L.: Epidemiological studies related to coronary heart disease: characteristics of men aged 40-59 in seven countries. Acta med. scand. Suppl 460 (1967). KEYS, A. (ed.): Coronary heart disease in seven countries. Am. Heart Ass. Monogr. 29 (1970). MORRIS, J. N.; KAGAN, A.; PATTISON, D. C.; GARDNER, M. J., and RAFFLE, P. A. B.: Incidence and prediction of ischaemic heart disease in London busmen. Lancet ii: 553-559 (1966). MORRIS, J. N.; CRAVE, S. P. W.; ADAM, C.; SIREY, c.; EpSTEIN, L., and SHEEHAN, D. J.: Vigorous exercise in leisure-time and the incidence of coronary heart disease. Lancet i: 333-339 (1973). NYGARD, K.: Subjective, medical, and social disability. Reports Inst. Oce. Health (in Finnish); Helsinki (1970). PAFFENBARGER, R. S.,jr.; LAUGHLIN, M. E.; GIMA, A. S., and BLACK, R. A.: Work activity of longshoremen as related to death from coronary heart disease and stroke. New Engl. J. Med. 282: 1109-1114 (1970). PAFFENBARGER, R. S., jr. and HALE, W. E. : Work activity and coronary heart mortality. New Eng!. J. Med. 292: 545-550 (1975). PUNSAR, S. and KARVONEN, M. J.: Angina pectoris and ECG abnormalities in relation to prognosis of coronary heart disease in population studies in Finland; in HALONEN and LOUHIJA Early diagnosis of coronary heart disease. Adv. Cardio!., vo!. 8, pp. 148-161 (Karger, Basel 1973).
Dr. S. PUNSAR, Finnish Heart Association, Research Programme, Koroistentie 6 f, SF-00280 Helsinki 28 (Finland)
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 3:12:01 PM
6
207
