Cholesterol and blood pressure role in modelling questioned.
Posted by bmhegde on 1
The modeling regarding 'deaths postponed' from cardiovascular causes is incomplete since it does not consider total mortality. The model basically looks at smoking (no argument there), blood pressure lowering and cholesterol lowering by diet and statins.
The fundamental unanswered question about blood pressure is: does artery hardening and decline cause an increase in blood pressure or, conversely, is blood pressure in fact causal to heart disease and the deaths it causes? There are to my knowledge no placebo controlled blood pressure lowering drug trials in women where a mortality benefit was found, for example the MRC trial (1) while there may be increased myocardial infarction in men from antihypertensives (2).
The fundamental cause or effect question about cholesterol is similar and there are indeed no intervention data that prove that dietary cholesterol or saturated fat reduction has a mortality benefit in anyone (3). Regarding women, it is now absolutely clear that statins will not reduce all-cause mortality (4) as is the case in anyone over the age of 70, as per the PROSPER trial (5).
The one conclusion in which the modelling supports the trial data is the inefficacy of statins, and where only 145 deaths were calculated to be postponed in England and Wales for each year of use in people without overt heart disease simply to lower their cholesterol.
Therefore, the assumption of causality of the aforementioned parameters of the model should be questioned. Cholesterol and blood pressure simply may not be 'causal' and confounders that may be, like homocysteine, omega-3 fatty acid intake and others must be figured in for modelling to give reliable outcomes. vos{at}health-heart.org
1. No authors listed. MRC trial of treatment of mild hypertension: principal results. Medical Research Council Working Party. Br Med J (Clin Res Ed). 1985 Jul 13;291(6488):97-104. MEDLINE 2861880.
2. Merlo J, Ranstam J, Liedholm H, Hedblad B, Lindberg G, Lindblad U, et al. Incidence of myocardial infarction in elderly men being treated with antihypertensive drugs: population based cohort study. BMJ. 1996;313:457-61. MEDLINE 8776312.
3. Hooper L, Summerbell CD, Higgins JP, Thompson LR, Capps NE et al. Dietary fat intake and prevention of cardiovascular disease: systematic review. BMJ 2001;322:757-63. MEDLINE 11282859.
4. Walsh JM, Pignone M. Drug treatment of hyperlipidemia in women. JAMA. 2004 May 12;291(18):2243-52. MEDLINE 15138247.
5. Shepherd J, Blauw GJ, Murphy MB, Bollen EL, Buckley BM, et al. Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial. Lancet. 2002 360(9346):1623-30. MEDLINE 12457784.
Competing interests: None declared