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LETTERS: Michael A Soljak, Malcolm E Kendrick, Steven M Laitner, Malcolm Law, and Nicholas J Wald Risk factor thresholds BMJ 2002; 325: 1114 [Full text]

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Lower threshold for blood pressure reduction does exist in clinical practice at least in the elderly

Albert FOURNIER, Gabriel Choukroun, Roxana Oprisiu, Claire Presne, Janette Mansour, François GUEYFFIER, Jean Miche Achard   (23 November 2002)

Lower threshold for blood pressure reduction does exist in clinical practice at least in the elderly 23 November 2002
Albert FOURNIER, Nephrology Department 80054 AMIENS CEDEX 1, Gabriel Choukroun, Roxana Oprisiu, Claire Presne, Janette Mansour, François GUEYFFIER, Jean Miche Achard Send response to journal: Re: Lower threshold for blood pressure reduction does exist in clinical practice at least in the elderly	EDITOR: in the correspondence about the article of Law and Wald 1 the authors claim that "there is no evidence of a threshold below which further modification of risk factors yields no further reduction in the risk of disease". Such evidence has actually been reported for both diastolic (DBP) and systolic (SBP) blood pressure, and precisely in the elderly. Cardiovascular risk was higher when the DBP was decreased bellow 76 mmHg in the metaanalysis of the European and Chinese elderly hypertension trials 2 , and below 68 mmHg in the SHEP trial3. Furthermore, the observational Rotterdam Study 4 showed a higher stroke risk in the treated hypertensive elderly when DBP was below 65 mmHg and SBP below 130 mmHg, whereas such a J curve was not observed in the non-treated population. This suggests that the deleterious effect of too much lowering BP is not the consequence of the low BP per se, but rather that once the threshold value is reached, at which the beneficial effect of lowering BP vanishes, a harmfull effect of the antihypertensive drugs is no longer balanced and therefore unmasked. A growing bundle of evidence indeed support the view that all antihypertensive drugs are not created equal, and that the various classes have protective or deleterious intrinsic effects on cardiovascular outcome independent of their BP effect. While in metaanalysis of randomized trials against placebo the observed cardiovascular risk decrease is comparable to that expected from the log- linear regression established in cohort studies, consideration of the nature of the antihypertensive treatment indeed shows that this apparent comparability actually results from mixing data of different drugs with opposite BP-independent cardiovascular effect. For instance, in the MRC 1985 trial, high dose thiazide and propranolol decreased DBP by 6 and 5 mmHg leading to expect a stroke risk reduction of 40% and 34% whereas the actual observed reduction were respectively 70% and 27%. In MRC 1992 low dose thiazide and atenolol similarly decreased DBP by 6,5 mmHg leading to expect a myocardial risk reduction of 26% whereas the observed reduction was respectively 40% and null. Thus we not only disagree with the lack of concern over lowering BP too far, at least in the elderly, but also with the idea that the choice of the drugs does not matter and therefore with the concept of strict reversibility of cardiovascular risk according to its log-linear regression with the BP-lowering effect of drugs. References 1. Soljak MA, Kendrick ME, Laitner SM, Law M, Wald NJ. Risk factor thresholds. Bmj 2002;325(7372):1114. 2. Blacher J, Staessen JA, Girerd X, Gasowski J, Thijs L, Liu L, et al. Pulse pressure not mean pressure determines cardiovascular risk in older hypertensive patients. Archiv. Intern. Med. 2000;160(8):1085-1089. 3. Somes GW, Pahor M, Shorr RI, Cushman WG, Applegate WB. The role of diastolic blood pressure when treating isolated systolic hypertension. Archi Intern Med 1999;159:2004-2009. 4. Voko Z, Bots M, Hofman A, Kovostaal P, Witteman J, Breteler M. J shaped relation between blood pressure and stroke in treated hypertensives. Hypertension 1999;34:1181-1185. Competing interests:   None declared