Dear Rod,
Re: reversibility of cardiovascular risk
> Dear Bruce - I have responded to others who have asked about reversibility
> -see my response to Toby Lipman:
>
> "Toby - Yes, I am saying that the difference in absolute risk between the
> early and late treated hypertensives will be very small and so the NNT very
> large. The evidence comes from comparing the effect of treatment in RCTs
> compared with the estimated difference in risk in cohort studies. What we
> find is that the predicted effect of lonterm differences in risk from
> cohort studies is very similar to the actual effects observed in trials."
My understanding of the trial evidence for hypertension is that
although it's an important risk factor for cardiac disease in cohort
studies, most of the effect in treatment trials is on stroke not CHD.
As I understood it, in the elderly you can show effects on CHD,
but in younger people you can't. One study I saw last year ( BMJ
1998; 317: 167-171) following a cohort of treated hypertensives
(said to be well controlled) and compared them to a matched control
group (not well described) and found double the cardiac mortality at
20 years in the hypertensives.
I've just quickly looked at the MRC trial of treatment of mild HT
again (17, 354 35-64 year olds with diastolics 90- 105) where you get
a small but significant decrease in stroke (RRR 45%, ARR
0.12%/patient year). There is no effect on coronary events - 222
in treatment group, 234 in placebo so the effect on all
cardiovascular events is solely due to the effect on stroke.
Forgive me if I'm being slow. I suspect there may be a meta-analysis
or similar somewhere which deals with this and I'd be interested in
any reference.
Thanks
Bruce
Bruce Guthrie,
MRC Training Fellow in Health Services Research,
Department of General Practice,
University of Edinburgh,
20 West Richmond Street,
Edinburgh EH8 9DX
Tel 0131 650 9237
e-mail [log in to unmask]
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