COMMUNITY HEALTH STUDIES VOLUME rr, NUMBER 2. 1978

DIMENSIONS OF PSYCHOLOGICAL PREDISPOSITION TO CORONARY HEART DISEASE

John SpiceP

Introduction

There is growing evidence that psychological factors are implicated in both predisposition to, and precipitation of, the various manifestations of coronary heart disease (CHD).[I] The bulk of studies in this area focus on the direction and magnitude of correlations between psychological characteristics and the prevalence of CHD, or of its known precursors. Little attention has been paid to the relationships within the set of psychological risk factors. The basic reason for this is simply that investigators have so far tended to examine only one or two of the suspected psychological risk factors at a time.

Elucidation of the structure of these risk factors is desirable for two main reasons. First, in the case of the major traditional risk factors- blood pressure, smoking and serum cholesterol level-it has been shown that their power to predict CHD is greatly enhanced if they are considered in combination. Even with the simplest form of combination, based on simple dichotomies, eightfold differences in coronary risk can be demonstrated.[2] This notion of a risk profile should also be applied to psychological characteristics to see if similar gains in predictive power are obtained.

The second consideration concerns intervention. Attempts to change traditional risk factors are greatly aided by the fact that these variables are embedded in theoretical structures which are firmly grounded on empirical fact. For example, knowledge about the determinants of Serum cholesterol level indicates that dietary change is a logical intervention strategy. In contrast, psychological risk factors lack a t h e o r e t i c a l f r a m e w o r k , d e s p i t e t h e i r strengthening empirical base. Yet attempts are already being made to modify coronary-prone behaviour. These attempts are much mote likely to succeed, and to avoid detrimental side effects, if we improve our understanding of the nature and inter-relationships of psychological risk factors.

The aim of the present study was to develop some hypotheses by analysing the inter- relationships of a set of six psychological characteristics, each of which is thought to be implicated in the development of CHD.[3] The characteristics were: the Type A behaviour

pattern, perceived work load, anxiety, depression, recent life changes and psychosocial assets.

Sample and Methods

The data set was obtained from a cross- sectional epidemiological study of associations between traditional and psychological CHD risk factors. Fuller accounts of the stud and its major results are reported elsewhere.[4fA simple random sample of 524 men, aged 30-55, was drawn from the Auckland electoral rolls. Maori and Polynesian subjects were excluded since the psychological measures used have not been standardised for these groups. Of the available and suitable subjects 77% agreed to participate. Comparison with census data showed that, within the selected age group, the sample was unbiased with respect to age, but contained an over-representation of subjects in the upper socio-economic groups. The vast majority (98%) of the sample was assessed under standard conditions at Auckland Medical School by the author. The remaining 2% were tested at their home or workplace.

The Type A person displays “enhanced p e r s o n a l i t y t r a i t s of aggres s iveness , ambitiousness and competitive drive, is work orientated with preoccupation with deadlines, and exhibits im atience and a strong sense of time urgency”.[5y Since this pattern is the best established of the psychological risk factors for CHD, it was studied in some detail using two measures. The most sensitive measure of the pattern, the Standard Situation Interview, was used to classify subjects as Type A or Type B (the relative absence of Type A character- istics).[6] Since this procedure is always open to observer reliability problems, subjects also rated themselves on the Vickers Rating Scale, an established nine item scale with known psychometric properties.[7]

Subjective or perceived work load was assessed with a slightly modified form of Caplan’s Subjective Quantitative Work Load Index.[8] On this scale subjects rate each of seven characteristics of their work load on a five point scale. Trait anxiety and depression were measured with short forms of two subscales from the Minnesota Multiphasic Personality

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Inventory, which Thiel and his colleagues have shown to be useful in the context of coronary risk.[9]

Recent life changes were assessed using an extended version of the Schedule of Recent Experience, modified for New Zealand use.[ 101 Subjects were shown a list of 60 events and asked to indicate which had happened to them in the preceding year. They then indicated the psychological impact of each event which had occurred by rating it on a five point scale ranging from ”very upset” through “unaffected” to “very thrilled”. From these ratings were derived “u set” and “thrill” scores, or what will be rezrred to as negative and positive stress ratings.

Finally, psychosocial assets were measured us ing a q u e s t i o n n a i r e d e v e l o p e d by Luborsky.[ 1 I] In this context, assets refer to such items as educational record, work history, number of friends and personal interests. An important point to note about the various measures used is that, with the exception of the recent events assessment, they are all established instruments with known psycho-metric characteristics.

Statistical Analysis

T o examine the s t ruc tu re of t he psychological variables a series of factor analyses was performed using the Statistical Package for the Social Sciences.[ 121 Factor analysis seeks to identify structural factors which run, like “common threads”, through some or all of the variables. In this instance, the major factors incorporated within the six psychological variables were identified, and quantified by measurement of the “factor loadings” (analogous to regression coefficients). The particular technique used (PA2) involves principal factoring with iteration and varimax rotation of factors.

Inspection of the scatterplots for each pair of variables indicated that the assumptions of linearity and homoscedasticity were justified. The number of subjects relative to the number of variables raised the possibility of sampling error. Accordingly, to test the stability of the factor structure the same analysis was performed on a number of random subsamples.

A further problem was raised by the non- normal frequency distributions of several of the variables. Where necessary, square root or log transformations were performed to normalise distributions. I t was found tha t such transformations made no substantive difference to the pattern of factor loadings. Accordingly the results reported are derived from analyses of untransformed variables. Following Nunnally’s recommendation to rotate approximately one third as many factors as there are variables, the first three factors were subjected to varimax rotation.[ 131 Also following Nunnally, significant factor loadings were defined as those with a value of at least 0.3.

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Results

The matrix of simple correlations between the variables is shown in Table I . Coefficients have been rounded to two decimal places. For this sample size a coefficient of .W is significant at the .05 level, and one of. I 1 is significant at the .01 level. Eight variables are shown since Type A behaviour was measured in two ways, and negative and positive stress scores, derived from the life change measure, were treated as separate variables.

TABLE 1 Simple Correlations Between Eight Psychological Variables

(N = 524)

Vorioblr (1) 0 (3) (4) 6) 16) V) ( I ) Type A (rating scdb) (2) Type A (interview) .. (3) Workload .......... .45** .3 I .. (5) Depression ......... .03 .01 .03 .42** (6) Ncptive alrcss ...... .18** .13** .IW 29.‘ 26.’ (7) Positive s1rcas ...... .08 .16.* .13** .13** .oO .17*’ (8) Psychosocial assets .. .03 .06 .08 -.I2’* -.27** -.14*’ .W

‘ 9 p < 0.01

.39**

(4) Anxiety.. .......... .43** .37** .40**

The factor analyses clearly showed that a stable three factor structure accounted for approximately 94% of the variance in the data. Table 2 shows a typical pattern of loadings on the three factors after varimax rotation. Again the figures have been rounded to two places. The loadings of interest are those which exceed 0.3.

TABLE 2 Loadings on Three Factor

Solution of Eight Psychological Variables After Varimax Rotation

(N = 524) Variable Factor

Type A (rating scale) .. .78 Type A (interview) .... .SO Workload ............ .58 Anxiety .............. .59 Depression ........... .03 Negative stress ........ .20 Positive stress ........ .I0 Psychosocial assets .... .07

I Factor .04 -.04 -.03 .42 .67 .40 -.04 -.43

2 Factor 3 .o I .20 .I3 .I4 .03 .34 .so .07

Discussion

Before examining the results two general points should be made. Factor analysis was used in the present investigation purely as an exploratory device to generate hypotheses for future etiological and intervention studies. Conclusions as to the general validity of the

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factor structure presented here must await further investigations. The second point concerns interpretation. Although factor analysis reveals the structure of a set of variables, the meaning of that structure must be supplied by the investigator. The aim of this discussion is to

rovide one interpretation of the present indings.

Factor I may be called the Type A syndrome, since this variable has the highest loading and is the best established of the psychological risk factors for CHD. The components of this syndrome are clearly Type A behaviour, workload and anxiety. Factor 2 will be referred to as the depression syndrome, which includes depression itself, psychosocial assets, and to a lesser extent, anxiety and negative stress. Finally, Factor 3 is clearly specific to the recent events measure, with significant loadings on both negative and positive stress only.

This pattern suggests that Factors 1 and 2 can be viewed as qualitatively different from Factor 3. Whereas the first two factors primarily reflect stable personal characteristics, the third is concerned more with perceived environmental qualities. This difference may, in turn, reflect the distinction between psychological redisposition

disease. Thus, it seems logical to view certain stable psychological characteristics as variables which somehow heighten the risk of a premature coronary event at some future time. In contrast, the experiencing of a number of life changes would be more relevant to the actual timing of the event. Hinkle, for example, has argued that life events are best seen as precipitators of myocardial infarction or sudden death in predisposed individuals.[ 141

The distinction does not mean that predisposing and precipitating factors are totally independent of each other. The pattern of correlations in Table 1 indicates that subjects' psychological characteristics, such as Type A behaviour and depression, are weakly associated with their negative stress scores. This may mean, for example, that Type As tend to seek out rapidly changing and potentially upsetting environments. Or that individuals with depressive tendencies experience distress in response to events which most would judge of no import. It is important to recognise both the conceptual distinction between predisposing and precipitating factors, and the fact that they interact.

Looking within Factor I , the Type A syndrome, it is interesting to note the relatively low correlation between the two Type A scores. This reflects the logical division of Type A characteristics into the attitudinal-motivational complex assessed by self-report measures, and the overt behavioural set detected by the interview technique. Various studies have shown that the self report portion of the pattern can

to, and precipitation of, mani P est coronary

itself be broken down into three parts, each of which appears to be differently related to the prevalence and incidence of CHD.[IS] Thus, although the present study treats Type A behaviour as a unitary phenomenon, etiological or intervention studies must take into account its multidimensional nature.

The strong positive correlation between Type A and perceived work load confirms findings reported by Caplan who used virtually the same self report measure on a sample of NASA employees.[l6] The presence of the work load variable in the Type A syndrome is consistent with Rosenman's clinical description of the Type A individual as "work-oriented".[ 171 However, it is not clear whether Type As look for, or perhaps create, demanding work environments, o r whether fortuitous and prolonged exposure to work pressures elicits the behaviour pattern. Undoubtedly both processes occur, even to one and the same individual. But the longitudinal studies which are necessary to unravel the health risks experienced by different psychological groups involved in different career patterns have yet to be done. The general fuzziness surrounding these questions is exemplified by the fact that, of the three components of Type A behaviour identified by factor analysis in various studies, the "job- involvement" factor has shown the least consistent association with coronary risk.[ 181

The presence of anxiety in the Type A syndrome is particularly noteworthy since investigators of psychosocial risk factors have tended to treat anxiety and Type A as distinct, independent variables. To make sense of the available data it is necessary to make two basic distinctions. Firstly, anxiety may be overt or covert according to the extent to which the individual expresses his or her feelings. Secondly, anxiety may be conceived of as a current state or as a predisposition to enter that state (trait anxiety). There is some impressionistic evidence that Type As do not generally display state anxiety but do tend to reveal otherwise covert anxiety and depression under appropriate assessment conditions.[ 191

In the present study predisposition to both anxiety and depression was measured. One interpretation of the presence of anxiety in Factor 1 is that there is a group of individuals who are predisposed towards both Type A behaviour and anxiety. However, since self control is fundamental to Type A behaviour, such individuals usually suppress their recurrent anxiety experiences. This raises the interesting question of whether the subgroup of Type As who are anxiety-prone are at greater risk of CHD, perhaps by virtue of their suppression activities, than are those Type As who are not predisposed to anxiety.

Turning to Factor 2, the depression syndrome, the presence of anxiety is consistent

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with its common occurrence in clinical depression. The loading on the negative stress variable probably indicates, not so much the tendency for depressives to experience many life changes, but, rather, for them to find almost any change inordinately distressing. Most striking is the inverse association between depression and psychosocial assets, a finding similar to that reported by Pinneau.[20] Although the nature of this relationship is as yet far from clear, its presence raises the possibility that depression, and thus some portion of coronary risk, may be Partially alleviated by strengthening of the individual's psychosocial supports. This notion of reducing disease risk by reinforcing supports is one which Cassel has discussed in some

deta%ll simplest predispositional hypothesis which the foregoing suggests is that there are two groups of coronary-prone individuals, one exhibiting the Type A syndrome, the other the depression syndrome as here defined. This suggestion has an interesting parallel in the findings of a study of post-infarct patients conducted by Kavanagh and Shephard.[22] Using the Minnesota Multiphasic Personality Inventory they found two psychological groups, one characterised by proneness to depression, the other by hypomania-a form of behaviour which clearly overlaps with the Type A pattern. Such a parallel is no more than suggestive, but is clearly deserving of further investigation.

An alternative possibility is that Factors 1 and 2 represent two phases of one process. Perhaps, in some cases, the Type A pattern attenuates over time and is replaced by the depression syndrome. Again the possibility arises that the Type A individuals who do finally succumb to depression are at greater risk of CHD than those who do not. Longitudinal data which would throw light on this question are lacking, but some cross-sectional findings are at least consistent with a phasic interpretation. It has been shown that the Type A pattern is less prevalent amongst older men.[23] This may, of course, be due to a high mortality rate amongst Type As, but the possibility of a psychological metamorphosis should not be excluded. Further, in the Kavanagh and She hard study the depressive subjects were signif!cantly older than the hypomanic group. In the present study composite scores on Factor 1 were negatively associated with age (r = -0.1068, p < .009), but Factor 2 scores and age were not significantly related.

Type A behaviour and state depression have been combined in another phasic model proposed by Glass.[24] Mainly on the basis of some striking results from laboratory studies he proposes that Type As oscillate more frequently and more intensely between active coping and giving up than do Type Bs. This alternating pattern is triggered by the repeated occurrence of

uncontrollable events to which Type As seemingly over-react. It is a small hypothetical step from this to suggest that, given sufficiently intense or rolonged exposure to uncontrollable events, a &al, irreversible shift from the active coping typical of Type As to the depressive premorbid state described by Engel may occur. This suggestion at least has the merit of being economical in that it combines Type A behaviour, depression and a particular category of life events into one coherent hypothesis.

The findings from the present study demonstrate tha t various psychological characteristics, which have been shown individually to influence risk of CHD, exhibit an interpretable three dimensional structure. Factor analysis is clearly a useful technique for organising and sim lifying data on psychological risk factors, and &r generating hypotheses for future investigation which take existing findings into account. It should be stressed, however, that any clarity achieved is partly due to certain oversimplifications. Firstly, the results of factor analyses are obviously dependent on the particular variables which are included. It is not suggested that the present study rovides a comprehensive hypothetical outline ofcoronary- prone behaviour. It should be contrasted, for example, with the work of Lebovitz et al. who have factor analysed the numerous personality correlates of CHD assessed by the Minnesota Multiphasic Personality Inventory, and isolated eight distinct factors.[26] Secondly, CHD has been treated as a single entity in the present discussion. In fact there is now increasing evidence that there are different psychological risk factors for different manifestations of the disease, notably for myocardial infarction and angina pectoris.[27] Thirdly, as noted earlier, individual variables such as Type A behaviour and psychosocial assets a r e themselves multidimensional rather than homogeneous entities.

The major implication of these comments for the development of hypotheses concerning psychological risk factors in CHD is that a multivariate approach is unavoidable. The notion that coronary-prone behaviour is reducible to a single personality dimension, or to exposure to a particular type of environmental stressor is untenable in the light of the evidence. There is now a need for a theoretical integration and elaboration of the nature of coronary prone behaviour to capture the complexity of those areas of human experience which appear relevant to coronary risk. Such an elaboration must take account not only of the structure of experience but also of its processes. Whether the investigator is concerned with the relationship between Type A behaviour and work load, or between depression and psychosocial assets, he must acknowledge the fact tha t such relationships change over time, and that the

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nature of that change may well be a critical determinant of coronary risk. As psychological theory in this area is systematically developed and fruitful hypotheses emerge, understanding of

the role of psychological risk factors in CHD etiology will progress more rapidly, and attempts at preventive action will be more likely to meet with success.

References

1.

2.

3.

4.

5.

6.

7.

Research Fellow, Department of Community Health, School of Medicine, University of Auckland. This research was supported by the National Heart Foundation of New Zealand. The author is very grateful to Professor J. R. P. French Jr. and Dr. R. Van Harrison for helpful discussions, and to members of the Biostatistical Unit in the Department of Community Health for statistical guidance. C. D. Jenkins: “Psychologic and social precursors of coronary disease” in New Eng. J. Med. 2845 (1971) pp. 244-255 and 284:6 (1971) pp. 307-317; and his “Recent evidence supporting psychologic and social risk factors for coronary disease” in New Eng. J. Med. 294:18 (1976) pp. 987-994 and 294:19

J. Stamler: “The National Co-operative Pooling Project in the United States” in G. Tibblin, A. Keys and L. Werko (eds): Pre- ventive Cardiology (Almqvist and Wiksell Stockholm 1972) pp. 43-53. Jenkins: “Psychologic and social precursors ...“ and “Recent evidence ...” J. Spicer, W. R. McLeod, K. P. OBrien and P. J. Scott: “Distributions and inter- relations of coronary risk factors in a community sample of Auckland men” in Aust. N.Z. J. Med. (Accepted for publication 1978); and Spicer et al: “Psychosocial correlates of coronary heart disease. Distributions and associations with traditional risk factors in a community sample of Auckland men”. (Submitted for publication 1978). R. H. Rosenman: “The role of behaviour patterns and neurogenic factors in the pathogenesis of coronary heart disease” in R. S. Eliot (ed.): Stress and the Heart (Futura Press New York 1974) pp. 123-141. R. H. Rosenman, M. Fricdman, R. Straus et al: “A predictive study of coronary heart disease: the Western Collaborative Group Study” in J. Am. Med. Ass. 189 (1964) pp.

R. Vickers: “A short measure of the Type A personality” . U n ~u bli s hed d ocu men t .

(1976) pp. 1033-1038.

15-22.

Institute for Social -Research, University of Michigan. (1973).

8.

9.

10.

11.

12.

13.

14.

15.

R. D. Caplan: Organisational stress and individual strain: A socio-psychological study of risk factors in coronary heart disease among administrators, engineers and scientists. Unpublished doctoral thesis, University of Michigan, Ann Arbor, 1971. H. G. Thiel, D. Parker and T. A. Bruce: “Stress factors and the risk of myocardial infarction” in J. psychosom. Res. 17 (1973)

R. H. Rahe, M. Meyer, M. Smith et al: “Social stress and illness onset” in J. psychosom. Res. 8 (1964) pp. 35-44. L. Luborsky, T. C. Todd and A. H. Katcher: “A self-administered social assets scale for predicting physical and psychological illness and health” in J. psychosom. Res. 17

N. H . Nie, C. H. Hull, J. G. Jenkins et al: Statistical Package for the Social Sciences (2nd edn. McGraw-Hill New York 1975). J. Nunally: Psychometric Theory (McGraw- Hill New York 1967). L. E. Hinkle Jr.: “The effect of exposure to culture change, social change, and changes in interpersonal relationships on health” in B. S. and B. P. Dohrenwend (eds): Stressful Life Events: their nature and effects (John Wiley and Sons New York 1974) pp. 9-44. K. F. Rowley and B. Sokol: “A review of

pp. 43-57.

(1973) pp. 109-120.

research examining the coronary-prone behaviour pattern” in .I. Human Stress 3:3 (1977) pp. 26-33.

16. Caplan: “Organisational stress and individual strain ...”

17. Rosenman et al: “A predictive study of coronary ...”

18. Rowland and Sokol: “A review of research

19. Rosenman et al: “A predictive study of coronfry ...” ; and Rosenman and M. Fried- man: Modifying Type A behaviour pattern” in J. psychosom Res. 21 (1977) pp. 26-33.

20. S. D. Pinneau: “Effects of social support on occupation stresses and strains”. Paper presented to the 84th American Psycho- logical Association Convention, September 1976.

21. J. Cassel: “Psychosocial processes and “stress”: theoretical formulation” in Int. J,

...

SPICER COMMUNITY HEALTH STUDIES 100

Health Sen . 4:3 (1974) pp. 417-481. 22. T. Kavanagh and R. J. Shephard:

"Depression after myocardial infarction" in Can. med. Ass. J. 113 (1975) pp. 23-28.

23. I. Waldron, S. Zyzanski, R. B. Shekelle et al: "The coronary-prone behaviour pattern in employed men and women" in J. Human Stress 3:4 (1977) pp. 2-18.

24. D. C. Glass: "Stress, behaviour patterns, and coronary disease" in Am. Scient. 65 (1977) pp. 177-187.

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25. G. L. Engel: "A life setting conducive to illness: The giving-up-given-up complex" in Ann. intern. Med. 69 (1968) pp. 293-300.

26. B. Lebovitz, E. Lichter and V. K. Moses: "Personality correlates of coronary heart disease: A reexamination of the MMPI data" in SOC. Sci. & Med. 9 (1975) pp.

27. Jenkins: "Recent evidence supporting psychologic ..." 207-219.

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