The type a behaviour pattern and physique

Journal ofPsychosomarrc Research, Vol. 21. No. 6. pp. 479-483, 1983. Printed in Great Britain.

THE TYPE A BEHAVIOUR

0022-3999/U 0 1983 Pergamon

$3.CO+.M) Press Ltd.

PATTERN AND PHYSIQUE

CLAUDIA KRAIUHIN*, EVIAN GORDON*, KAE BAKER*, RUSSELL MEARES*+ andALmHOWS0N-f (Received 5 November

1982; accepted in revisedform

12 April 1983)

Abstract-This study examines the possibility that Type A behaviour is related to physique, and thus, is secondary to physique as a risk factor for coronary heart disease (CHD). Scores on a modified version of the 1966 Jenkins Activity Survey were correlated with a number of physical parameters. Age was found to have the highest correlation of -0.177. When the effects of age were adjusted for, only 7.1% of variation in JAS scores was explained by the body measurements used to define physique. In addition, when high and low scorers on the JAS were compared, no significant differences were found between the groups on any of the body measurements. Since this study found no significant relationship between JAS scores and physique, the results do not controvert the supposition that Type A behaviour is an independent risk factor for CHD.

INTRODUCTION

A CONSIDERABLE body of evidence has shown that the Type A behaviour pattern is associated with the incidence of coronary heart disease. This association holds even after the effects of well-known risk factors for CHD are statistically controlled [ 1,2,3]. However before concluding Type A behaviour is an independent risk factor for CHD, the role of body-build or physique needs to be examined. A possibility which has not previously been investigated is that a particular kind of body-build may be associated with Type A behaviour, and thus with CHD. If this is the case, the risk associated with Type A behaviour may be secondary to that arising out of body-build. The predisposition towards a particular body-build is to an extent genetically controlled, thus, if Type A behaviour is associated with certain features of bodybuild it should show evidence of heritability. As yet there is no evidence for heritability of the Type A behaviour pattern as a whole. However, a study by Rahe, Hervig and Rosenman 141 of twins showed that responses on a number of scales which tap characteristics in common with Type A behaviour did show evidence of heritability. These characteristics were rapid body movements, forcefulness and speed, which suggested to the authors that a heritable dimension of heightened psychomotor activity was associated with Type A behaviour in their study. Similarly, Buss and Plomin [5] revealed that activity level (which is strongly and positively related to Type A behaviour) shows evidence of heritability, and Rosenman, Rahe, Borhani and Feinleib [6] found Factor H (hard-driving) of the Jenkins Activity Survey had a modest genetic component in 56 sets of twins. The studies cited suggest that at least some components of Type A behaviour may be related to heritable factors which manifest themselves in heightened physical activity. The aim of this paper is to study directly the relationship between Type A and physique. *Department of Psychiatry, University of Sydney, Westmead Centre. tSchoo1 of Economics, Macquarie University. *Correspondence and requests for reprints should be addressed to: Professor ment of Psychiatry, Westmead Centre, Westmead, N.S.W. 2145, Australia. 479

Russell Meares,

Depart-

CLAL~DIAKRAIUHIN, EVIAN GORDON, KAE BAKER, RUSSELLMEARES and ALAN HOWSON

480

METHOD Subjects 187 voluntary

male Caucasoid

subjects

between the ages of 28 to 64 were examined.

Measurement of Type A behaviour Items from the 1966 edition of the Jenkins Activity Survey, obtained from the article by Zyzanski and Jenkins [7] were amended to read in the first person and given a response option of ‘yes’ or ‘no’. Each response option was evaluated as indicating either a Type A or Type B response, and Type A responses scored one point each. Subjects thus received a score out of 57 indicating the strength of their Type A behaviour pattern. Subjects who scored 2 40 were considered Type A individuals and those scoring < 20 were considered Type B individuals. This method did not allow for scoring of the separate Type A components, namely, speed and impatience, hard-driving and competitive and job involvement. Measurement of body build The following measurements were taken. 1. Age 2. Height (cm.) 3. Weight (kg.) 4. Width of shoulders (Bi-deltoid diameter) (cm.) diameter) (cm.) 5. Width of hips (Bi-Trochanteric 6. Abdominal girth (measured through the umbilicus) (cm.) 7 Subcutaneous fat (measured by skinfold calipers laterally, at the level of the umbilicus). (mm.) 8. Hairgrowth on chest. A four-point rating scale was used: 0 = no hair growth on sternum or around mamillae. 1 = slight hairgrowth on sternum or around mamillae. 2 = moderate hairgrowth on chest and around mamillae. 3 = profuse hairgrowth on chest, around mamillae and also between the sternum and umbilicus 9. Hairgrowth on head. Again, a four-point rating scale was used. 0 = no hair 1 = little hair 2 = average, that is, in between 1 and 3. 3 = profuse hairgrowth. Height lO.Ponderal Index = B 4Weight Statistical analyses The objective of analysis was to ascertain and the various body measurements.

whether

a relationship

exists between Type A behaviour,

age

Analyses of the whole sample Firstly, each predictor variable was correlated with scores on the JAS. An age effect was observed and partial correlation coefficients adjusted for age were determined. Secondly, a multiple regression model with the following adjustments was fitted to the data: (a) A square root transformation of the JAS scores was performed to stabilise the variance, since the scores, being counts of binary variables, have their variances proportional to their expected values

PI. (b) The two ordered (c) Residual analysis

variables (hair on head and hair on chest) were represented by indicator variables. was performed and plots drawn to check that the model assumptions were tenable.

Analyses comparing Type A and Type B subjects Subjects scoring 2 40 on the modified JAS were grouped as Type A’s and those scoring G 20 were grouped as Type B’s, To construct a model which predicts the probability of a subject belonging to a particular group, the multiple logistic regression procedure was implemented [9]. The BMDP stepwise regression programme [IO] was used to select predictors in a stepwise manner and estimate the coefficients for the fitted model. Lastly, a multivariate test of the equality of the group means for all variables (excluding the two ordered variables) was conducted after the normality and homogeneous variance assumptions had been checked. Each variable was then tested using the univariate 2 sample t-test, and the ordered variables were tested using the Mann-Whitney test corrected for ties [I 11.

Type A behaviour

and physique

481

RESULTS

Nineteen subjects (10.15%) scored Z 40 on the modified JAS classified Type A. Thirty-three subjects (17.65%) scored 6 20 and Type B. The percentage of Type A subjects identified using this method the findings of the Western Collaborative Group study (cited in Frank revealed that 10% of the general population are Type A individuals.

and were thus were classified conforms with er al. [l]) which

Results of analyses on the whole sample Table I reveals that the correlation coefficients between scores on the JAS and the body measurements are of a relatively small order. Age has the largest correlation; the negative sign ((0.177) indicating there is a tendency for Type A scores to decrease with increasing age. TABLE I.--coBBELATION THE BODY

MEASUREMENTS

COEFFICBWT?, AND

BETWEEN

SCORES

ON THE

JAS (n = 187) Body Measurement

Age Height Weight Shoulders Hips Waist Skinfold Hair on chest Hair on head Ponderal index r* represents

r

r*

-0.177 0.037 0.023 0.020 X1.062 0.029 -0.001 0.149 0.074 -0.006

-0.005 0.041 0.025 -0.033 0.027 0.085 0.079 0.098 -0.060

the partial correlation after adjusting for age.

coefficient

The table also shows that when the correlations are adjusted for the effects of age, there is comparatively little change in their magnitude. The multiple regression analysis of all variables including age yielded R 2 = 0.099. That is, when all the predictors are taken into account they explain only about 9.9% of the variation in JAS scores for the whole sample. Inclusion of the interactions term did not substantially change the value of R2, just an increase to 0.107. When age was adjusted for in the model, only about 7.1% of variation in JAS scores was explained by the body measurement predictors. When age was ignored, the R2 value only changed to 0.072. This implies that for all purposes, we would not be too far in error if we ignore the age variable when a model is fitted of JAS scores against the body measurement variables.

Results of analyses comparing Type A and Type B subjects Table II, which presents mean body measurements of Type A and Type B subjects reveals little difference between the two groups. The stepwise regression program selected age as the only predictor to categorise subjects as either Type A or Type B. Thus, information regarding the body measurements will not in this case improve the prediction of the probability of being in either group.

482

CLAUDIA KRAIUHIN, EVIAN GORDON, KAE BAKER, RUSSELLMEARES and ALAN HOWSON TABLE II.-MEAN

BODY MEASUREMENTSOF TYPE A AND SUBJECTS

Body Measurement

TypeA(n=19) SD X

Height (cm) Weight (kg) Shoulders (cm) Hips (cm) Waist (cm) Skinfold (mm) Hair on chest Hair on head Ponderal index

1766.30 81.32 461.16 343.84 898.32 15.26 2.20 1.50 414.39

68.40 8.51 22.82 12.35 59.05 6.89 0.61 0.88 27.88

TYPE B

Type B (n = 30) SD 57 1748.50 77.21 450.82 342.91 877.61 13.94 1.90 1.20 413.10

64.00 14.82 25.27 23.29 108.01 7.72 0.60 0.74 25.02

The multivariate test of the equality of group means for all variables, excluding those two with ordered categories, yielded a Hotelling’s T 2 with p < 0.58. The same order of p-values were obtained when each variable was tested using the univariate 2-sample t-test. For the two ordered variables, the Mann-Whitney test resulted in p-values of < 0.20. It is concluded from these analyses that the body measurements account for little of the variation in Type A scores and that as far as this sample is concerned, no significant difference exists between Type A’s and Type B’s on the various body measurements. DISCUSSION

No study has previously attempted to relate the Type A behaviour pattern with physique. In this study a negative correlation was found between age and scores on the JAS. Other studies have similarly reported a negative correlation between measurements of Type A behaviour and age [2, 3, 121. When the effects of age were adjusted in the multiple regression analysis, only 7.1% of variation in JAS scores was accounted for by the body measurements. In addition, when high and low scores on the JAS were compared, that is, Type A and Type B subjects, no significant differences were observed between the two groups on any of the body measurements. It was concluded that for this sample of men there is little relationship between JAS scores of Type A behaviour and the body measurements taken. A number of methodological limitations in this study need to be pointed out however, as they bear on the conclusions which can be drawn from the findings. Firstly, the variability of physical constitution was described by numerous, isolated, anthropometric measurements. This description of human physique fails to communicate much information about body shape. Secondly, the JAS was not scored for its individual factors. It is possible that physique or body shape is associated with some components of the JAS but not the whole behaviour pattern. Further studies are therefore needed which assess total body shape, by using somatotyping for example, and which score the JAS for its individual components. With these limitations in mind, it is proposed that the results of this study do not controvert the supposition that the Type A behaviour pattern is an independent risk factor for coronary heart disease.

Type A behaviour

483

and physique

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