11
Hypertension in the US
diagnosis of left ventricular hypertrophy. Circulation 40: 185-195 (1969). Scott, R.C.: The correlation between the electrocardiographic patterns of ventricular hypertrophy and the anatomic findings. Circulation 21: 256-291 (1960). Author's address: Professor M.G. McCall, University Department of Medicine, Perth Medical Centre, Shenton Park, WA 6008 (Australia).
Discussion Dr G.E. Bauer (Sydney): On the question of nomenclature, I think we should be rather careful to use the term 'borderline hypertension' in a specific way. Most papers dealing with the subject take a different group, less severe than 95 to 109mm Hg diastolic, as being borderline hypertension. Dr G.S. Stokes (Sydney): Prof. McCall, what were the correlation coefficients for your ECG voltage function with change of blood pressure?
Prof. McCall: Correlation coefficients for the relationship between the ECG function and change in systolic blood pressure in the long-term treatment group were of the order of 0.65 (p145/89 >149/95 >155/99 >159/99 >165/99
>149/95 >155/99 >159/105 >1651105 >169/105
2. Diastolic only
> 110 'High' any age > 105 'Moderate' any age > 100 'Moderate' 21-54 yrs only
WHO classification (mmHg) HH [HB BB [Bn N
;;. 160/96 ;;. 160 or;;' 96] 140/90 - 159/94 ;;. 140 or;;' 90] < 140/90
cases that we had using our 'Napier' classification with that obtained by using the WHO classification. The total prevalence of hypertension which is demonstrated by the WHO classification is rather alarming: 16% of the population classified as hypertensive and a further 26.6% classified as borderline, which leaves merely 57% of the population as normal. We think this is very unrealistic. To have had to refer some 40% of our subjects back to their doctors for consideration would have been a great embarrassment for us and for the medical profession of Napier, and certainly would have overloaded the clinics. On the other hand, using the sliding scale shown in table I we feel that although we were somewhat conservative in classifications, about 6.8% required referral. The prevalence of treatment has, of course, also to be considered. I believe there is some place for mass screening for hypertension but I certainly agree with Prof. Lovell that until such time as we can be quite sure of the criteria we have for selection that it would be unwise to try and attempt it on a really big scale. But I would welcome comments on what sort of classification we should adopt as we certainly ought to adopt it internationally. Dr G. Berglund (Goteborg): Prof. Lovell, what is your
Napier survey 1973
Napi..
WHO
Napier
N-2535 WHO £.2"
Napier
WHO
NaPl«
WHO
WHO (Goteborg modification) Age group (years)
Blood pressure (mmHg)
20-29 30-64 65+
150 and/or 90 160 and/or 95 170 and/or 95
< 40 Age group.
4()'S9
High
High
Moder.t.
High/borderline
Average
conducted in Napier in 1973 we took a random 10% population sample which amounted to 2,600 people of which we were fortunate enough to get 97% attending. Table I shows the sliding-scale (age-adjusted) classification that we regard as clinically appropriate and also sets out the WHO classification. Fig. 1 compares the yield of
~60
o
Totll.
Borderline/normal
Napier
WHO
Classification
Classification
Fig. 1. Napier and WHO classification of blood pressure levels.
Panel discussion
conclusion from the figures you showed from the Albury study that 80% of hypertensives have seen a doctor and 65% had their blood pressure taken, and still only 12% were on antihypertensive medication? To me that means that general practitioners either do not recognise high blood pressure as being dangerous to their patients or they take the blood pressure in a different way, probably after a longer rest. Prof. Lovell: The 80% attendance is an estimate made last month (Sept 1975). The treatment rate estimated last month is between 20 and 25% in that age group. The 12% was the rate of treatment 4 years ago. Treatment has practically doubled and so that partly answers your question. What do I read into the 80%? I qualified what I read into it by saying I do not know how representative it is. I think it is not very wide of the mark because the other figure I know of is Holland's for London where he found that if you took a sample of people within a general practice the great majority of adults saw their doctor at least once every four years. If people are seeing their doctor so frequently it seems to me that this question of 'to screen or not to screen' almost vanishes. What you do - as I see it - is to educate the doctors and the public who are going to their doctors for all sorts of things, to the idea that every few years, according to age, the blood pressure should be measured. Dr Berglund: I think that is about the llgure that we have in Sweden too - that 95% see their doctor within a 3-year period. Dr Labarthe, you have brought down the number of hypertensives in the USA from 26 million to 9 million, but I think you have forgotten that you have to keep checking the blood pressure in very many millions. Where you find one high blood pressure and then a low one, then you have to follow the subject for many years perhaps with repeated blood pressure measurements. Dr Labarthe: That is so; any single value can be interpreted usefully only in relation to the overall scheme of detection and follow-up of high blood pressure. Clearly we have an immense task if we were to undertake systematic screening of the total population to identify all the hypertensives. It is equally clear that there are insufficient resources to do this job. In this sense I would certainly agree with Prof. Lovell that mass screening of the total popUlation is not feasible. However, as epidemiologists, I think we have an opportunity to identify and concentrate our resources on high-risk groups with respect to undetected hypertension - just as we do in finding high risk groups for other conditions. In our own circumstances in the USA, we know that there are rural populations, black populations, and socio-economically disadvantaged populations who are not participants in the 70 or 80 or 90% IJgure for frequent medical contact. In those groups, I think
17
systematic screening programmes are essential unless we are to sit by and see the continuation of a very great burden of disease which we have an opportunity to prevent. Dr Stokes: I would like to offer a comment in relation to an earlier question to Prof. Lovell about combining screening for hypertension with mass tuberculosis (TB) surveys. We have had for some years at Sydney Hospital an anti-TB chest X-ray unit which offers a chest X-ray service to passersby; a service which is a function of previously existing legislation requiring periodic chest X-rays. We simply placed a nurse in this little listening post and she took the blood pressures of those willing to have this done. About 98% of those who were asked submitted, and 10,000 people were screened over a period of 2 to 3 years. The cost of screening was extremely low, around 70c per person. The prevalence of hypertension detected by this survey agrees approximately with the data that Professor Lovell presented. There is no time to comment fully on the fruits of this, but I would like to disagree sharply with what was said about this type of service. I do feel there is a real place for agencies such as this which would allow us, at very low cost, to screen large sections of the community. I don't believe a tremendously biased result will be obtained, and although this method may not be suitable for epidemiological purposes, its treatment benefits I feel are very significant. A number of patients that came to us via this survey were found to have severe complications of hypertension, potentially reversible. Our policy was to try and get these people to go back to their family doctor. We found that approximately one-third of those whose local doctors had been notified about their hypertension received subsequent treatment. This is, perhaps, some indirect confirmation that they were able to substantiate our Imdings. Also we have done a I-year follow-up on a subset of these patients and found that there was a considerable concordance between the two blood pressure readings a year apart, particularly of course in those who had received no treatment in between.
Panel Discussion: Risk Factors for Hypertension
Chairman: Professor F.O. Simpson (Dunedin)
Prof. Simpson: Hypertension is of course a risk factor in vascular disease of various parts of the body. On this account we do our best to lower blood pressure in those in whom it is raised. In essential hypertension we do this mainly by pharmacological means but the question is whether we cannot also do something about the factors which are thought to be, at least in part, responsible for raising blood pressure.
18
Symposium on hypertension
Table I. Mean systolic blood pressures of relatives of hypertensives (RI and population controls (el - males plus females; age grouping 40 to 59
Percentage of persons with pressures at or exceeding certain stated levels Casual
Basal
Supplemental
mm Hg
e
R
mmHg
e
R
mmHg
e
R
180+ 160+ 140+
Hypertension in the US
diagnosis of left ventricular hypertrophy. Circulation 40: 185-195 (1969). Scott, R.C.: The correlation between the electrocardiographic patterns of ventricular hypertrophy and the anatomic findings. Circulation 21: 256-291 (1960). Author's address: Professor M.G. McCall, University Department of Medicine, Perth Medical Centre, Shenton Park, WA 6008 (Australia).
Discussion Dr G.E. Bauer (Sydney): On the question of nomenclature, I think we should be rather careful to use the term 'borderline hypertension' in a specific way. Most papers dealing with the subject take a different group, less severe than 95 to 109mm Hg diastolic, as being borderline hypertension. Dr G.S. Stokes (Sydney): Prof. McCall, what were the correlation coefficients for your ECG voltage function with change of blood pressure?
Prof. McCall: Correlation coefficients for the relationship between the ECG function and change in systolic blood pressure in the long-term treatment group were of the order of 0.65 (p145/89 >149/95 >155/99 >159/99 >165/99
>149/95 >155/99 >159/105 >1651105 >169/105
2. Diastolic only
> 110 'High' any age > 105 'Moderate' any age > 100 'Moderate' 21-54 yrs only
WHO classification (mmHg) HH [HB BB [Bn N
;;. 160/96 ;;. 160 or;;' 96] 140/90 - 159/94 ;;. 140 or;;' 90] < 140/90
cases that we had using our 'Napier' classification with that obtained by using the WHO classification. The total prevalence of hypertension which is demonstrated by the WHO classification is rather alarming: 16% of the population classified as hypertensive and a further 26.6% classified as borderline, which leaves merely 57% of the population as normal. We think this is very unrealistic. To have had to refer some 40% of our subjects back to their doctors for consideration would have been a great embarrassment for us and for the medical profession of Napier, and certainly would have overloaded the clinics. On the other hand, using the sliding scale shown in table I we feel that although we were somewhat conservative in classifications, about 6.8% required referral. The prevalence of treatment has, of course, also to be considered. I believe there is some place for mass screening for hypertension but I certainly agree with Prof. Lovell that until such time as we can be quite sure of the criteria we have for selection that it would be unwise to try and attempt it on a really big scale. But I would welcome comments on what sort of classification we should adopt as we certainly ought to adopt it internationally. Dr G. Berglund (Goteborg): Prof. Lovell, what is your
Napier survey 1973
Napi..
WHO
Napier
N-2535 WHO £.2"
Napier
WHO
NaPl«
WHO
WHO (Goteborg modification) Age group (years)
Blood pressure (mmHg)
20-29 30-64 65+
150 and/or 90 160 and/or 95 170 and/or 95
< 40 Age group.
4()'S9
High
High
Moder.t.
High/borderline
Average
conducted in Napier in 1973 we took a random 10% population sample which amounted to 2,600 people of which we were fortunate enough to get 97% attending. Table I shows the sliding-scale (age-adjusted) classification that we regard as clinically appropriate and also sets out the WHO classification. Fig. 1 compares the yield of
~60
o
Totll.
Borderline/normal
Napier
WHO
Classification
Classification
Fig. 1. Napier and WHO classification of blood pressure levels.
Panel discussion
conclusion from the figures you showed from the Albury study that 80% of hypertensives have seen a doctor and 65% had their blood pressure taken, and still only 12% were on antihypertensive medication? To me that means that general practitioners either do not recognise high blood pressure as being dangerous to their patients or they take the blood pressure in a different way, probably after a longer rest. Prof. Lovell: The 80% attendance is an estimate made last month (Sept 1975). The treatment rate estimated last month is between 20 and 25% in that age group. The 12% was the rate of treatment 4 years ago. Treatment has practically doubled and so that partly answers your question. What do I read into the 80%? I qualified what I read into it by saying I do not know how representative it is. I think it is not very wide of the mark because the other figure I know of is Holland's for London where he found that if you took a sample of people within a general practice the great majority of adults saw their doctor at least once every four years. If people are seeing their doctor so frequently it seems to me that this question of 'to screen or not to screen' almost vanishes. What you do - as I see it - is to educate the doctors and the public who are going to their doctors for all sorts of things, to the idea that every few years, according to age, the blood pressure should be measured. Dr Berglund: I think that is about the llgure that we have in Sweden too - that 95% see their doctor within a 3-year period. Dr Labarthe, you have brought down the number of hypertensives in the USA from 26 million to 9 million, but I think you have forgotten that you have to keep checking the blood pressure in very many millions. Where you find one high blood pressure and then a low one, then you have to follow the subject for many years perhaps with repeated blood pressure measurements. Dr Labarthe: That is so; any single value can be interpreted usefully only in relation to the overall scheme of detection and follow-up of high blood pressure. Clearly we have an immense task if we were to undertake systematic screening of the total population to identify all the hypertensives. It is equally clear that there are insufficient resources to do this job. In this sense I would certainly agree with Prof. Lovell that mass screening of the total popUlation is not feasible. However, as epidemiologists, I think we have an opportunity to identify and concentrate our resources on high-risk groups with respect to undetected hypertension - just as we do in finding high risk groups for other conditions. In our own circumstances in the USA, we know that there are rural populations, black populations, and socio-economically disadvantaged populations who are not participants in the 70 or 80 or 90% IJgure for frequent medical contact. In those groups, I think
17
systematic screening programmes are essential unless we are to sit by and see the continuation of a very great burden of disease which we have an opportunity to prevent. Dr Stokes: I would like to offer a comment in relation to an earlier question to Prof. Lovell about combining screening for hypertension with mass tuberculosis (TB) surveys. We have had for some years at Sydney Hospital an anti-TB chest X-ray unit which offers a chest X-ray service to passersby; a service which is a function of previously existing legislation requiring periodic chest X-rays. We simply placed a nurse in this little listening post and she took the blood pressures of those willing to have this done. About 98% of those who were asked submitted, and 10,000 people were screened over a period of 2 to 3 years. The cost of screening was extremely low, around 70c per person. The prevalence of hypertension detected by this survey agrees approximately with the data that Professor Lovell presented. There is no time to comment fully on the fruits of this, but I would like to disagree sharply with what was said about this type of service. I do feel there is a real place for agencies such as this which would allow us, at very low cost, to screen large sections of the community. I don't believe a tremendously biased result will be obtained, and although this method may not be suitable for epidemiological purposes, its treatment benefits I feel are very significant. A number of patients that came to us via this survey were found to have severe complications of hypertension, potentially reversible. Our policy was to try and get these people to go back to their family doctor. We found that approximately one-third of those whose local doctors had been notified about their hypertension received subsequent treatment. This is, perhaps, some indirect confirmation that they were able to substantiate our Imdings. Also we have done a I-year follow-up on a subset of these patients and found that there was a considerable concordance between the two blood pressure readings a year apart, particularly of course in those who had received no treatment in between.
Panel Discussion: Risk Factors for Hypertension
Chairman: Professor F.O. Simpson (Dunedin)
Prof. Simpson: Hypertension is of course a risk factor in vascular disease of various parts of the body. On this account we do our best to lower blood pressure in those in whom it is raised. In essential hypertension we do this mainly by pharmacological means but the question is whether we cannot also do something about the factors which are thought to be, at least in part, responsible for raising blood pressure.
18
Symposium on hypertension
Table I. Mean systolic blood pressures of relatives of hypertensives (RI and population controls (el - males plus females; age grouping 40 to 59
Percentage of persons with pressures at or exceeding certain stated levels Casual
Basal
Supplemental
mm Hg
e
R
mmHg
e
R
mmHg
e
R
180+ 160+ 140+
