data were adjusted to allow for systematic differences between (a) submaximal and maximal tests and (b) bicycle, step and treadmill exercise. We have adequate comparative data to know that the corrections we applied were appropriate for young subjects, and even at this end of our graphs there was the disquieting suggestion that the Saskatoon people of 1973 were less fit than the Toronto people of 1966. Dr. Gumming may well be right in suggesting that in older subjects bicycle data diverge more widely from treadmill and step test results; certainly our own results from Saskatoon, soon to be published, support his view. However, his claim of a 40% systematic discrepancy between maximum test results and submaximum predictions of aerobic power is less well founded. Rowell, Taylor and Wong (op cit) are the only people who have found this enormous error, and the reason seems to be that their subjects had tachycardia due to an overheated room and impending or actual cardiac catheterization. In contrast, our room temperature was well controlled and we were able to attain quite a lighthearted atmosphere through mass testing; tachycardia with its attendant problems of data interpretation was thus largely avoided. The relative merit of expressing results as absolute oxygen intake or as values relative to body weight and to lean mass continues a matter of controversy. We would agree that values relative to body weight penalize the obese, but insist this is a fair penalty to impose on the average citizen, since the added body mass must be moved about and* places an extra load on the heart. For the endurance athlete in weight-supported sports the absolute oxygen intake is a more appropriate criterion. Lean mass is difficult to measure accurately and is also highly correlated with maximum oxygen intake; it is thus of doubtful value to express oxygen intake relative to lean tissue mass. The important points that should emerge from our article are that Canadians in one prairie city are less fit than they could be with regular exercise and are less fit than the AHA has recommended they should be. Assuming other cities have comparable statistics it is quite probable that the underlying lack of activity adds to the spiralling costs of health care, and it would be a pity if efforts to generate a more active lifestyle were to become dissipated because people can point to a lively controversy in a medical journal and say "The experts do not agree." Roy J. SHEPHARD, MD, PH D

Professor of applied physiology School of Hygiene University of Toronto Toronto. Ont.

Screening for hypertension To the editor: After reading the excellent presentation "Two epidemiologists discuss the myths, and realities of health maintenance" (Can Med Assoc 1 109: 1146, 1973) and other similar sceptical views on the value of periodic health examinations and multiphasic screening, it was with some bewilderment that I read the uncritical praise in Dr. Jacques Genest's editorial "The hypertensive patient" (Can Med Assoc 1 111: 747, 1974) of the mass screening program for hypertension carried out by Dr. Donald S. Silverberg and his group and reported in the same issue of CMAJ. It is not my intention to enter into a controversy here as to whether or not mild hypertensives (what is "mild" anyway?) should be subjected to longterm, and possibly costly, drug therapy. Some years ago the question was raised in CMAJ "What do you do with the asymptomatic hypertensive patient anyway, beyond telling him to relax presumably having first made him tense with one's meddling?" Apparently there are others more knowledgeable on the subject than I who believe otherwise. However, at a time when we are all being exhorted to stem the escalation in costs of health care, I wonder whether we would be acting responsibly in artificially generating more, at present symptomless, patients, many of whom would be left for the rest of their lives with yet another degree of anxiety about their future. As for the locale for such procedures, if they cannot be carried out in the quiet of a doctor's office, why not somewhere peaceful such as a massage parlour or a cocktail bar? Personally I can think of few situations more likely to produce fluctuating blood pressure values in both wife and husband than shopping expeditions. W. E. MACBEAN, MB, BS, DPH

82 Burnhamthorpe Rd. Islington, Ont.

To the editor: Dr. MacBean draws attention to one of the points of controversy regarding therapy in hypertensive patients. It concerns the advisability or appropriateness of longterm treatment of "mild" hypertension. Dr. MacBean is so right in also asking "what is 'mild' anyway?" I would like to reaffirm my conviction, however, that the work carried out by Silverberg et al deserves praise because I believe it represents an important contribution to the welfare of the community and of the hypertensive patients detected by this type of screening. Many leading specialists and researchers in this field have given a great deal of attention in the last few

years to this matter. After much thought, many discussions and in-depth examination of the whole problem, the United States Department of Health, Education and Welfare, the American Heart Association, the Canadian Heart Foundation, the Canadian Kidney Foundation and many other private institutions have recommended a fullscale attack on the problem of hypertension because of its high prevalence in the North American population and because of the repeated demonstration that its control will greatly decrease the risk of severe cardiovascular complications. I believe it is important that a person know whether or not he has essential hypertension and, if he does, that it is adequately managed and treated. It would appear that Dr. MacBean prefers to let more severe hypertension and more extensive arterial disease develop in these people because attempts to control the hypertension might further "the escalation in costs of health care" or might generate a temporary state of anxiety in the patient who is aware he has hypertension. Is this a reasonable attitude? I am a specialized consultant in this field to whom many physicians have been and are being referred for evaluation and treatment, and it has always struck me that all of these physicians without exception have requested a full evaluation in hospital and have demanded treatment even if their hypertension was considered "mild". How does one justify treatment for members of the medical profession and a different attitude for hypertensives outside the profession whose disease is undetected or inadequately treated? JACQUES GENEST, FRCP[C]

Scientific director Clinical Research Institute of Montr6al Montreal, Que.

To the editor: Dr. MacBean raises five points with regard to our article "Use of shopping centres in screening for hypertension" (Can Med Assoc J 111: 769, 1974). He intimates that long-term treatment of asymptomatic hypertension may not be indicated. Although this was a common view some years ago, the evidence is now very strong that persons with diastolic blood pressure persistently more than 104 mm Hg should be treated. Although preliminary data from studies on persons with diastolic pressures of 90 to 104 mm Hg suggest that complications are much more common in the untreated, only time will prove if this is correct. The second point he raises is whether there is a cost saving in screening for hypertension. If intravenous pyelography, renal angiography and uri-

CMA JOURNAL/JANUARY 11, 1975/VOL. 112 21

Letter: Screening for hypertension.

data were adjusted to allow for systematic differences between (a) submaximal and maximal tests and (b) bicycle, step and treadmill exercise. We have...
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