ENVIRONMENTAL FACTORS IN CORONARY ARTERY DISEASE

Transcription

1 ENVIRONMENTAL FACTORS IN CORONARY ARTERY DISEASE KENNETH SANDERS, M.D. London The role of environmental factors in the aetiology of coronary artery disease is not known. The following table (adapted from Morris, 1956) lists some of the suggested factors involved, and their possible roles: TABLE I Protecting factors Low fat diet Habitual physical activity Lower income group Alcohol Predisposing factors High intake of animal fat Cigarette smoking Nervous strain Obesity The literature on the subject is, to put it mildly, extensive, and one hesitates to add to it. However, a recent investigation into obesity in coronary artery disease (Sanders, 1959) involved the comparison of a group of patients with a control group of healthy people matched for sex (male), age (35-75) nationality (British), place of domicile (north-west London) and religion (Christian); they were also well matched for height, weight, and relative weight (table II). TABLE II MEAN WEIGHT, RELATIVE WEIGHT, HEIGHT AND AGE IN PATIENTS AND CONTROLS Patients (n = 48) Controls (n = 52) Mean S.D. Mean S.D. Weight (lb) Relative weight (per cent) Height (cm) Age (yr) It seemed to me to be worth while to question the two groups J. COLL. GEN. PRACT., 1960, 3, 336

2 CoRoNARY ARTERY DLsEAsE 337 about their dietary habits, and also about certain other factors in their lives. Only 47 agreed to answer the questions on diet. Investigation Cases and controls were questioned on: 1. Smoking. The number of cigarettes, or the amount of tobacco smoked daily (in the cases, at the time of the attack): pipe tobacco was not differentiated from cigarette tobacco, and one ounce of tobacco per week was taken to be equivalent to four cigarettes daily (Doll and Bradford Hill, 1952). 2. Physical activity. (a) Occupation. This was graded into light, medium or heavy according to a table constructed for this purpose (Morris et al., 1953) and loaned by the London Hospital Social Medicine Research Unit. (b) Exercise. Three questions hours were asked: about activity outside working (i) Do you walk or cycle to work regularly? (ii) Do you take an active part in sport, or at what age did you stop doing so? (iii) Do you work regularly in a garden? From the replies, I estimated the degree ofphysical activity as average, below average, or above average. 3. Income. Each individual was asked to place his weekly income into the appropriate group, according to the classification used by the Ministry of Agriculture and Fisheries: Al. over 24 weekly C. 6-9 weekly A weekly D1. less than 6 weekly B weekly D2. pensioners 4. Nervous factors. Three questions were asked:- (i) Do you consider yourself to be a nervous person, compared with the average? (ii) Have you ever attended a doctor with " bad nerves " or been given a " nerve tonic "? (iii) Have you ever had to stay away from work with nervous trouble? Depending on the answers, each subject was scored 0, +, or + +, to indicate an increasing scale of nervousness. 5. Diet. Each person was asked to complete a questionnaire which, based on a suggestion by Yudkin (personal communication, 1957) was designed to give a rough estimate of amounts of fat, both animal and vegetable, consumed in the diet (appendix). Results The answers to the first factors were tested for statistical signi-

3 338 KENNE SANDs ficance by the method of chi-squared (table III). TABLE III SIGNiFICANCE TESTS FOR FIVE ENVIRONMENTAL FACTORS Significance Cases Controls x' n p Smoking cigarettes daily < > Occupational grade activity Light Moderate <.5 Heavy 5 5 Exercise grade Above average Average Below average 12 8 Income grade Al + As 6 7 B <.7 C+D1+D Nervous grade temperament <05>02 ++ ~~18 8 TABLE IV DiET QUESTIONNAIRE-ANALYSIS OF ANSWERS BY FREQUENCY DISTRIBUTION 47 Cases 52 Controls 1. Number of slices of buttered bread daily 2 or less r or more Number ofslices of margarined bread daily 2 or less or nore,

4 CORONARY ARTERY DISEASE I TAsLE IV-contunued Cases 1 52 Controls 3. How spread Thin Moderate Thick Amount of milk drunk daily ipint i Over 2 pints Frequency of cream consumption Daffy 2 1 Weekly 10 4 Less than weekly Frequency of ice-cream consumption Daily 6 2 Weekly 13 8 Less than weekly Frequency of cheese consumption Daily Weekly Less than weekly Frequency of fried food consumption Daily Weekly Less than weekly Cooking medium Animal fat mostly Vegetable fat mostly 5 4 Both Suet consumption Often 8 3 Occasional Never Meat fat consumption All Most.. I Some None Egg consumption per week 2orless m1 2 7 S I 9 or more Discussion The results in table III show no significant difference between the two groups, although the trend in all cases except income is in agreement with the current hypotheses. There is nothing in table

5 340 KENNE SANDERS IV to suggest any difference in intake of fat, whether animal or vegetable, between the two groups. These results seem to be in agreement with the views of Yudkin (1957) and Morris (1959). Summary Forty seven patients with coronary artery disease were compared with fifty two healthy controls in respect of dietary fat, smoking, occupation, exercise, income and nervousness. No significant difference was found, but trends in line with current hypotheses were discemable. Acklowledgments I should like to thank Professor John Yudkin of the Department of Nutrition Queen Elizabeth College, University of London, for suggesting the form of the diet questionnaire, and Dr S. Finlay of the Department of Student Health, University of Leeds for his advice. REFERENCES Doll, R. and Bradford Hill, A., Brit. med. J, 2, 1271 Ministry of Agriculture, Fisheries and Food, Domestic Food consumption and expenditure H.M.S.O. Morris, J. N., Heady, J. A., Raffle, P. A. B., Roberts. C. G. and Parks, J. W., Lancet, 2, 1053, 1111 Morris, J. N., Brit. J. industr. Med., 13, 287 Morris, J. N Lancet, 2, 967 Sanders, K., ibid, 2, 432 Yudkin, J., 1957, ibid, 2, 155 APPENDIX This questionnaire is designed to find out what kinds of fat you eat, and how much. Perhaps whoever does your cooking may be able to help you with answers. Please put a circle round the answers that apply in your case, and bring the completed paper with you. (1) How many slices of bread do you eat each day? 2or less; 3 or4; 5 or 6; 7 or 8; 9 or more. (2) Of these how many do you spread with butter? With margarine? with meat or chicken fat? (3) Do you spread them thinly; moderately; thickly? (4) How much milk do you drink each day, in tea, coffee, milky drinks, milk puddings, or on cereals? J pint or less; J to 1 pint; I to 2 pints; over 2 pints. (5) How often do you have fresh cream? (6) How often do you have ice cream? (7) How often do you eat cheese? (8) How often do you eat fried food? (9) At home is your food fried mostly in lard or dripping; oil; vegetable cooking fat; butter. (10) How often is suet used in your food? often; occasionally; never. (11) How much of the fat on meat do you eat? all; most; some; none. (12) How many eggs do you eat each week?