International Health News

Cholesterol and stroke risk

LONDON, ONTARIO, CANADA. It is a common belief that elevated cholesterol is a risk factor for stroke. On the webpage of the US NIH National Institute of Neurological Disorders and Stroke (updated October, 2014) one finds "Excess LDL can cause cholesterol to build up in blood vessels, leading to atherosclerosis. Atherosclerosis is the major cause of blood vessel narrowing, leading to both heart attack and stroke". This NIH webpage gives a way of calculating stroke risk. Eight risk factors are given: age, systolic blood pressure untreated, systolic blood pressure, diabetes, smoking cigarettes, having a history of cardiovascular disease, atrial fibrillation or left ventricular hypertrophy. Numerical points are given to each risk factor. Add up the points and look up the 10-year probability of a stroke. Incidentally, this approach presented in 2014 is taken directly from a 1994 report based on the Framingham study.

What happened to LDL cholesterol mentioned in the NIH introduction? Certainly cholesterol was on the minds of the Framingham investigators. In fact it was a very big deal and launched almost universal cholesterol testing, dietary avoidance and the demonizing of this chemical vital in human biochemistry and present in cell walls. Ultimately the result was a significant fraction of the older members of the populations in the developed world were on statins and other cholesterol lowering drugs. It appears that the Framingham study could not find a significant association that would motivate them to include the LDL level in their point system calculator. Furthermore, as your editor has pointed out many times in this newsletter, the notion that circulating cholesterol drives atherosclerosis is falsified by a large number of studies based on autopsy results and more importantly, imaging of coronary artery plaque. There is no correlation. Consistent with this, cholesterol lowering has no impact on coronary artery calcium scores or coronary plaque progression.

However, it is part of the conventional wisdom that statins reduce the risk of stroke. Dr. David Newman, MD has examined the literature to obtain the absolute risk reduction. For individuals without known heart disease, the number needed to treat to prevent one event was 154 over 5 years whereas if there was a history of heart disease, it was 125. Converging these into percentages of those treated who do not benefit, we get 99.5% and 99.2%, respectively (see Individuals at risk need something a lot better than this.

Ware WR. The mainstream hypothesis that LDL cholesterol drives atherosclerosis may have been falsified by non-invasive imaging of coronary artery plaque burden and progression. Medical Hypotheses 2009; In press

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