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8' NOVEMBER 1989 NEW ZEALAND MEDICAL J©URNAL f a'7- `57-> 593 r > to c~ Correspondence Letters to the editor should be siQned by all authors, typ.wrttten in double spacinp, and not exc..d !00 words of~taxt excluding ref.renc.s. References should be in the 1laneouver style. Over-lona letters may be shorten.d wfthout refer.nce to the auttwrs unleas it is apecifically stated' that thhr may not. Passive smokinp and passive thinkin rises to unacceptable levels not only implies an arguable value judgment on their part but is illogical and t supported by any evidence that I know, thougb it has to acknowledged as a possibility. No trial has ahowa that def treatment confers benef5t tnone has been designed' t~o d sol. and although left v6mtricvlar bypertropby an regresa .vi aome forms of trastmenI (generally:,tbe ezpensive onea!I there evidence that permanent ultraatructitral changes occur in the yocirdlum. Common sense suggests that trxtment should staeced as soon as a proper diagnosis aecordiag to current 'delines is made. I noted the subtk chaage ia ideatity of the decision maker from the doctor to tbe patiea tbe caae o! my hypothetical 30 year old. This raises in sting questions. Whose is the responsibility if the patie t makes the wrong decision?' ls it nalistie to expect him to view his deasion at regular intervals. and if so. on what gro ds will be neverse it? Will'this happen before or after tbe t of hemiplegia or dyspnoea'.', TDe drug aide eff are important for the patient and as s determinant of the eraII ratio of costs to benefits. I believe the point I was mak4ia clear enough and''I' leave it to practitioners to decide from t,lieu experience whether side effects such as impotence are le4ersibk on srithdrawal'of the offending agent or E o, q Mr Lee's objeetion to the evidkaee on passive smoking (NZ Med ~ L J 1989: 102: 5391 hingea on his theory that miaclaaaifiution of ~ g t a proportion of smokers as nonsmokers might explria the observed associ.tion between passive smoking and lung caacer. ~ C However his own book on the subject It{, which he cited. is itself a 100-page monument to bias. In it, be makes an exhaustive exploration of the possibility that smokers are miar3asaified as nonsmokers, while completely ignoring the fact that' the smoking habits of the spouse are equally likely to be miicllusified, thus biasing the relative risk estimate towards 1.0. Given the widespread exposure to passive smoking in society. it ia likely that epidetttiologic studies so far have underestimated the megnitude of risk. J udgtng by his remarks on Hirayami s study 1YL. Mr Lx does not appear to have realised that the age and occupation- standardised rate ratios for ischaemic heart disease have been reported' for 117 year follow up 12I The age and occupation- standardised figures were similar to the rate ratios standardised for age only 121. We have a complimentary copy of this paper available should Mr Lee wish to read' it. As witti Mr Lee. the views we express ars always our own, However, we do not receive any tees when we express them. Perhaps this helps dkrify the issue of miscJkssification, which is really verrv straightforward. and almost invariably l.ads to an underestimation of the passive smoking effect. lchiro Kawachi. Department of Community Health. Neil Pearce;, Welliagtan School of Medicine. Wellington. I I.w P\ M~.clusil~cawenol ae.okae6 l.GU and puuw.sn,olun6Arerr.of Ne ..gsenc- ln~awn.l ArcWve" of Qnvp.uaWand H..IdA, Suppement. Hrddbrrir Spr»rer S'er1.6..198f 2 H u..am. 7 l.unf euutr m JLpan eM.cu of eumum..nd.n po.Nw noekeg In Mu.tl A1 [one.Peoi1.~nR c.neer caura snd yrev.os.mm he. YorkVri.6 C6kmr 1 eirrn. uonal 19F.. 17695 Treatment of hypertension Kawachi and Purdie s neply lNZ Med J 1989: 102: 5401 to my letter I1I raises important issues in the debste about the benefits of' treating hypertension. Two main points require serious consideration. The first is contained in the advice that I should consult their data pertaining to treatment at a blood' ressure greater than 100 mmHg 121, and to accept that ~ex dau represent the expected gain with treatment if h rtension is treated according to the recently published gui lioes.,This is wrong. The advice fails to recognise that e definition of hypertension by trial~ protocols is quite erent from that suggested by recent guidelines. and it is not cult to show that trial patients are unrepresentative of th A.ger population and are at lower risk even at equal~levelry o~' lood pressure because of e:clusion criteria and the method o lection. A patient whose diastolic blood'pressure is 100 afta several readings taken over a reasonable time interval ' t higher risk than if select.ed' from a low risk populatio on the basis of screening measurements. In the place treaaed group of the MRC trial. whose records I am t1y studying, the unadjusted cardiovascular event rate t entry for those with diastolic blood pressure greater than I mmHg an-30221 was 8.1v1000?yr. but in those with the s blood pressure 3 months into the trial /n-1198i~ lequivaJent to a definition of hypertension more in keeping with the,,giiidelinesl the corresponding figure was 10.3 l.%lillar and Levkr. unpublishedl: This illustrates that current guidelines havE the effect of identifying a subset of patients with a greater risfr. thereby optimising the efficiency of treatment measured as the number of patients treated per event avoided. in this case 373 versus 116 respectively. These figures are much lower than those presented by Kawaehi and Pludie 121. The second point relates to the long term benefits of treatment.. This is a complex and important issue which cannot be fully addressed here. Suffice to say that Kawachi and Purdie's ' suggestion that treacment can be deferred until the blood pressure not. A previous-'paper from my cornespondents' department has compared IudfavourablyJ the cost of treating hypertension with cardiac traAsplantatron Isl. and the ciear implication from their publicatiqLs is that they regard the treatment of' mild hypertension as prohibitively eapensive., We have agreed with their canclusion. up to a point µ.5{.! but have provided cost benefit analyses baaed on both trials of treatment and current management guidelines. It would be instructive to see similar calculations from Kawachi and Purdie. JI A Millar. MRC Blood Pressure Uhit. 4t-'estern lnfirmarv. Glasgow - G11 BNT. Scotland. UK. I Mill4 JA.'Rvtnrat e(.hyprtr.aarYm A2M.d J 1999 )0Y47e2K...du I. Pu+dx G SSr b.e.lru aed n.k. of u+at.n6 mald u om.rav hYp-so KZM.d'J 1969. 102 3714 Naieoim L. J~duoo R. K..aW l. Sae~u R 1. tJr PAarvi.edoneal vutm.m ol ~m~k 3 bocdnrr hyp•rt.n.ao aaa'.H.cuw m NaYr pwmyn4ae` 12M.d J 196F101 i 16' 71 4 Mill.r JA. H.nro PC.'tnr.emmin ot uosuo6 mdd nyp.rten.ao !:ZM.d J1.i6l. 70) T75 S 1[illi.r JA. Han.mPC. E~ to.u.ud'bn.fiu of u..ws6 aWd hvpen.o.m. rrqWu frm . vo.. r.cuoe.) moS.l TZ M.EJIY66..J01 623'5 Diet and behaviour I write in response to the leading artick.. Diet an ' ehaviour (NZ Med J 1989: 102: 499u l am the mother of t eliildren as well as being a general practitioner. Chtr 3+.o- year d daughter is food sensitive. and I have no doubt that the gestion of food's or additives that, dis.gt~e .vith her esux eunaratiag behaviour.. dark aii des under her eyes. night +v g f 1.30 am-4.30 am); loss of appetite. intrtasaf' thirst. vul tis and joint p.ins. These reactions have been confirmed several occasions by Ioften inadvertenti challenge tests. ave been manipulating her diet for a year with excellent res s and improved sleep. and contest that. far from a nega ~ e effect, ir has develbped great responsibility and con in her S year old'sisur that she should not be ezposed to C s that make her ill. Critical observa ' n iias long been the backbone of medical practice. Accura deductions have been made before the process in question w derstood: We need' look no further than the develbpment' vaceination by Edw•ard Jenner. the correlation between h dwashing and puerperal infection noted by lgnaz Semmdw ss and the discovery of penicillul by Ale=ander Ffemin Parehts and teachen are ttie, people best able to assess the behaviour of children. Early and subtle beliaviour changes ve urtlllcely to be noticed by independent researchers who do oot kdow the children. We also are not aware of the cumulative effect pf these small behavioural ehaages on the .ducational life of t:be