Does the patient whose risk is reduced by lowering cholesterol then become a
"new" person with a new cholesterol level - or do they become a "non trial"
person whose risk has already been altered. I believe the former - after
all, the patients entering trials have had interventions in lifestyle
(admittedly not changing a lot in most cases ) throught their life - from
intoxicated medical student with appalling diet - to well behaved husband
with exercise and better diet - to stressed GP with lots of antioxidant - i
guess i am saying that patients are not ever cross sectional but are on a
continuum. Practically I plug the numbers in (my own Framingham based risk
evaluation program in Visual Basic with lots of colours but no graphs!) for
the patients to see the options for change - none point out that they could
do everything! - they are too realistic.they then change - their BP drops or
whatever - 12 months later I plug the numbers in again and show them what
new options are available - the process is ongoing -
martin
Dr Martin Dawes
Director Centre for Evidence Based Medicine
University of Oxford
Nuffield Department of Medicine
John Radcliffe Hospital
OXFORD OX3 9DU
----- Original Message -----
From: James McCormack <[log in to unmask]>
To: EBM <[log in to unmask]>
Sent: Monday, March 13, 2000 9:54 PM
Subject: Independent risk factors
> The last couple of messages have alluded to the issue of independent risk
> factors and if the benefit of treating more than one risk factor is
> additive.
>
> To date, as far as I am aware, all the multiple risk factor intervention
> trials have shown no clinical benefit - Systematic review of randomised
> controlled trials of multiple risk factor interventions for preventing
> coronary heart disease - BMJ 1997;314:1666 - 7 June
>
> In addition, if you reduce your cholesterol the chance of CHD decreases by
> 30%; if you treat your hypertension you reduce your chance of CHD by 20%
and
> if you treat your diabetes you reduce it by 25% and if you stop smoking
you
> reduce your chance by 40%. These numbers add up to 115% which is
impossible
> unless you are able to decrease the chance of CHD in the person standing
> next to you.
>
> In this regard, I have a couple of questions for the group:
>
> 1) If one reduces so called independent risk factor why does that not
> produce additive benefits?
>
> 2) In cohort studies where risk factors have been shown to be independent
by
> covariance analyses - does it mean that they should produce additive
effects
> when applied to patients with multiple risks. They appear not to, so why
> not? Are they really completely independent or just different enough to
> produce a statistical difference?
>
> 3) When covariance analyses are done on data from RCT's to show
independent
> effects does that mean that these interventions should produce additive
> effects?
>
> Any help to clarify these issues would be appreciated.
>
>
> Dr James McCormack
> Associate Professor
> Faculty of Pharmaceutical Sciences
> University of British Columbia
> Vancouver, B.C.
> 604) 822-1710
> [log in to unmask]
>
>
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