13th March 2018
Before putting cardiovascular disease to bed for a while and talking about other things – such as diabetes – I thought I should highlight a fact that is almost never remarked upon yet is extremely important. At least it is, if you trying to bring down the cholesterol hypothesis. The fact is this. A raised cholesterol level, or LDL level, is not a risk factor for stroke. Not even in familial hypercholesterolaemia (FH) is a raised cholesterol level a risk factor for stroke.
Here, I am quoting from a study published in the Lancet called ‘Cholesterol, diastolic blood pressure, and stroke: 13,000 strokes in 450,000 people in 45 prospective cohorts. Prospective studies collaboration.’
‘After standardization for age, there was no association between blood cholesterol and stroke except, perhaps, in those under 45 years of age when screened. This lack of association was not influenced by adjustment for sex, diastolic blood pressure, history of coronary disease, or ethnicity (Asian or non-Asian).’ 1
I think that this was a big enough study to demonstrate that, if there is any effect, it can only be tiny. Yes, the study is over twenty years old, but it was done before statins came along to distort the entire area. By which I mean after the mid-nineties, a large number of people with raised cholesterol were being put on statins, thus making any interpretation of the impact of different cholesterol levels, on stroke, almost impossible.
As for Familial Hypercholesterolaemia. The findings of the Simon Broome registry (set up in the UK to study the health impact of FH) were, as follows
‘The data also confirm our earlier findings that FH patients are not at a higher risk of fatal stroke.’ 2
Thus, a raised cholesterol level is not a risk factor for stroke, even at very high levels found in FH – even in homozygous FH (where both the subject’s genes are faulty so leading to more severe FH). Yet, and yet, statins reduce the risk of stroke. Not by much, and not to the extent that I consider the benefits to outweigh the harms, but they do. Here, plucked from a million possible articles is something from the American Heart Association
‘Millions more people worldwide may benefit from cholesterol-lowering statins after a global study showed the drugs help reduce heart attacks and strokes in people at moderate risk. The risk fell slightly further when patients also took blood pressure drugs.’ 3
The absolute figures wobble about, depending of which of the myriad studies and meta-analyses you choose to look at, but the reduction in stroke risk is about the same as the reduction in the risk of heart attacks/myocardial infarctions.
When I see facts like this, I try to use logic. The logic, in this case, goes something like this:
- Factor A (raised LDL) is not a risk factor for disease B (stroke)
- However, if you lower factor A, the risk of disease B falls
Conclusion. Something other than the lowering of Factor A is causing the reduction in the risk of disease B. If you take this thought one step further, the beneficial effect of statins on the risk of stroke, flatly contradicts the cholesterol hypothesis.