THE EFFECT OF MENTAL STRESS ON THE EOSINOPHIL. Samter, 1951]. According to Rud [1947] there is a large fall between early morning

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1 THE EFFECT OF MENTAL STRESS ON THE EOSINOPHIL LEUCOCYTE COUNT IN MAN.' By A. C. KERR.2 From the Institute of Physiology, University of Glasgow. (Received for publication 2nd Augu8t 1955) A FALL in the concentration of circulating eosinophil leucocytes (eosinophils) has been shown to occur in man and in various animals during acute infections, after immersion in cold water, and after surgical and electrical shock. Injections of a sympathomimetic drug, of insulin, and of a large variety of poisons have the same effect. This fall is probably produced through the agency of adrenocortical and anterior pituitary hormones [Dalton and Selye, 1939; Rud, 1947; Laragh and Almy, 1948; Gabrilove, 1950; Recant, Hume, Forsham and Thorn, 1950; Abelson and Moyes, 1950; Kuhl and Ralli, 1951; Best and Samter, 1951]. Variations in the eosinophil concentration in normal human beings have not attracted so much attention, but it is known that there are considerable short-term fluctuations and that there is a diurnal variation. According to Rud [1947] there is a large fall between early morning and midday. This is succeeded by a quick rise just after twelve o'clock, followed by a slow rise during the afternoon and evening. His findings have been largely confirmed by Fisher and Fisher [1951] and Donato and Strumia [1952]. The effect of physical activity on the eosinophil count does not seem to have been studied. Humphreys and Raab [1950] found in medical students that there was a significant eosinopeiiic response to the stress of a written examination. The present investigation was made to study variations in the concentration of the circulating eosinophils in students practising dental mechanics and in students practising operative dentistry under normal and under examination conditions. METHOD Freely flowing blood was taken from a stab wound in the end of the middle finger of the left hand. Blood was drawn up to the niark 1 While this work was being done, the author was in receipt of a Nuffield Foundation Fellowship Award. 2 Present address: Department of Dental Medicine, Guy's Hospital, London, S.E.1. 18

2 Mental Stress and Eosinophil Count one in a white cell pipette and Hinkleman's [1923] diluent to the mark eleven. The fluids were mixed by rotating and shaking the pipette by hand for one minute. After discarding one-third of the mixture the chambers of a Fuchs-Rosenthal heemocytometer were filled by capillation. For each count the whole fields of two 32 mm.3 chambers were examined using a strong light and with a magnification of 90. When repeating the procedure on any one individual, the same pipette and pair of chambers were always used so that errors of calibration of pipettes and of chambers would not affect the comparability of the counts. 19 SUBJECTS AND EXPERIMENTAL CONDITIONS The subjects were 23 male students of dentistry in the University of Glasgow, who were all between 20 and 30 years except for one aged 40 years. All were in good health and had had no recent illnesses. One of them (M4) had a definite history of hay fever. None of the others gave any history of allergic disorders. The subjects were in three groups designated E, 0 and M. Group E consisted of 5 subjects, group 0 of 9 subjects and group M of 9 subjects. In all cases four eosinophil counts were made between 2 and 6 p.m. at approximately hourly intervals. During this period the eosinophil count in normal subjects is said to show a steady rise [Rud, 1947; Fisher and Fisher, 1951]. While the counts were being made, the students in group E were being examined in practical operative dental surgery as part of their final examination for the Licentiate in Dental Surgery. The test took the form of the preparation and filling of a tooth cavity. It was, unfortunately, not possible to carry out subse(uent control counts on group E, with the examination stress absent. Those of group 0 were engaged in routine operative dental surgical practice. Those of group M were practising dental mechanics, mostly sitting at the laboratory bench. RESULTS In figs. 1, 2 and 3, changes in the eosinophil count with time are shown, the second, third and fourth counts being expressed as percentages of the first. In the two normal groups 0 and M (figs. 1 and 2), the fluctuations in the count appear to be random and there is no fall of more than 35 per cent of the first count. In the examination group, E (fig. 3), four of the subjects showed a steady fall in the serial counts to a value more than 80 per cent below the first count. In the fifth subject the serial counts were almost constant.

3 TIME OF DAY. (P.M.) FIG. 1.-Variations in the afternoon eosinophil count in 9 subjects practising operative dental surgery under normal conditions. The second, third and fourth counts are expressed as percentages of the first count. In no case is there a fall greater than 25 per cent of the initial value. TIME OF DAY. (P.M.) FIG. 2.-Variations in the afternoon eosinophil count in 9 subjects practising dental mechanics. The second, third and fourth counts are expressed as percentages of the first count. In no case is there a fall greater than 35 per cent of the initial value.

4 Mental Stress and Eosinophil Count 21 TIME OF DAY. (P.M.) FIG. 3.-Variations in the afteroon eosinophil counts of 5 subjects practising operative dental surgery under final degree examination conditions. The second, third and fourth counts are expressed as percentages of the first count. In subject E5, who showed no signs of anxiety, the level was steady. In the other subjects there was a fall of more than 80 per cent of the initial value. STATISTICAL TREATMENT To make statistical comparisons between the groups the value of - was calculated for each subject: b is the gradient of the regression of the four counts and is obtained by evaluating the expression Y. c is the intercept of the regression on the y axis and is obtained from the equation c = y - bx, since the regression passes through the point x, the arithmetic mean of the x terms. It was then possible to compare the serial changes in the different groups by calculating t, the ratio of the difference between two means to its standard error. Reference to tables of t values gave an estimate of the probability that the two groups belonged to the same population.

5 22 Kerr The results of these calculations (Table I) confirm the impression that the difference in the changes in the eosinophil counts in subjects TABLE I.-RESULTS OF COMPARING THE CHANGE OF THE EOSINOPHIL COUNT WITH TIME IN SUBJECTS PERFORMING THREE ACTIVITIES E = examination. 0= operative dentistry. M =dental mechanics. Groups Value for Degrees of Probabilitv compared t freedom El to 4: E > P > El to 4: M+O > P M : > P > 0-3 El, E2, E3 and E4 compared with the change in subject E5 is highly b significant (0-01 > P > 0-001). The mean value of - for the first four c members of group E who were under examination stress differs with very high significance (0.001 > P) from the same index for the combined groups 0 and M who were not under examination stress. Between the two non-examination groups there is no significant difference in the values for the change with time in the concentration of eosinophils in the blood (0.4> P> 0.3). DISCUSSION Before the investigation it was expected that the physical strain of carrying out dental surgical operations might lead to a lower concentration of circulating eosinophils in the operating group, 0, than in the group, M, sitting at the laboratory bench. It soon became evident that this expectation was not fulfilled. The similarity of the present findings in men operating and in men doing dental mechanics to Rud's [1947] values for resting normal subjects suggests that these activities were not producing stress. On the other hand, during the examination the two examiners and the observer formed the opinion that four of the five examinees were suffering from considerable mental stress. The fifth man appeared to be unworried by the situation and was very confident about his ability to pass the examination. When the eosinophil counts were completed, it was evident that the stressed examinees all showed a large fall in concentration of eosinophils, while the confident examinee's eosinophil count remained steady. The latter student passed the examination easily. Of the other four, one was a good pass, two just passed, and one was rated a poor failure. The results show that a single eosinophil count is of little value. They suggest, too, that if a patient is anxious and exposed to stress, as he may well be when first examined by a hematologist, his eosinophil count is likely to be abnormally low.

6 Mental Stress and Eosinophil Count 23 SUMMARY 1. Hourly eosinophil counts were made in the afternoon on five students engaged in their final examination in operative dental surgery. Four showed a fall of more than 80 per cent; these were obviously anxious. In the fifth the count remained steady; he was unperturbed by the examination. 2. Similar counts on nine subjects performing routine operative dentistry and on nine subjects engaged in routine dental mechanics showed no constant downward trend and no fall greater than 35 per cent of the initial count. 3. The difference between the group under examination stress and the other groups was very highly significant. 4. It is concluded that the mental stress associated with a serious examination can produce a significant fall in the eosinophil count during the examination. A similar influence may be at work in some patients being subjected to medical investigations. ACKNOWLEDGMENTS I wish to thank Professor R. C. Garry and Drs. A. W. Sloan and J. B. de V. Weir of the Institute of Physiology, University of Glasgow, for advice and encouragement during this investigation. I am also greatly indebted to Professor J. Aitchison and Dr. J. Ireland of the Glasgow Dental Hospital and School for clinical facilities, and to the subjects for their willing co-operation. REFERENCES ABELSON, D. and MOYES, E. N. (1950). "Ephedrine in a screening test for cortisone substitutes", Lancet, ii, 50. BEST, W. R. and SAMTER, M. (1951). "Variation and error in eosinophil counts of blood and bone marrow", Blood, 6, 61. DALTON, A. J. and SELYE, H. (1939). "The blood picture during the alarm reaction", Folia Hcemat. 62, 397. DONATO, R. A. and STRUMIA, M. M. (1952). "An exact method for the chamber count of eosinophils in capillary blood and its application to the study of the diurnal cycle ", Blood, 7, FISHER, B. and FISHER, E. R. (1951). "Observations on the eosinophil count in man: a proposed test of adrenal cortical function ", Amer. J. med. Sci. 221, 121. GABRILOVE, J. L. (1950). " The level of the circulating eosinophils following trauma", J. clin. Endocrinol. 10, 637.

7 24 Kerr HINKLEMAN, A. J. (1923). "Hematometric differential counting", J. lab. and clin. Med. 8, 196. HUMPHREYS, R. J. and RAAB, W. (1950). "Response of circulating eosinophils to nor-epinephrine, epinephrine and emotional stress in humans", Proc. Soc. exp. Biol. and Med. 74, 302. KUHL, W. J. and RALLI, ELAINE P. (1951). "Effect of acute stress upon blood constituents, white cells and urine constituents in normal individuals", J. clin. Endocrinol. 11, 776. LARAGII, J. H. and ALMY, T. P. (1948). "Changes in circulating eosinophils in man following epinephrine, insulin and surgical operations", Proc. Soc. exp. Biol. and Med. 69, 499. RECANT, L., HuME, D. M., FORSHAM, P. H. and THORN, G. W. (1950). "Studies on the effect of epinephrine on the pituitary-adrenocortical system ", J. clin. Endocrinol. 10, 187. RUD, F. (1947). "The eosinophil count in health and in mental disease", Acta psychiat. et neurol., Suppl. 40, 1.