Strokes are probably more feared than heart attacks, because a serious one can rob you of your most valued faculties: your mind or your mobility. Because of what they do to the patient, they also represent a costly burden on the heath service. Wouldn't it be nice if we knew what caused them?
It turns out that we do ... sort of. Or at least we have some tantalising pointers that hint at what NOT to do if we want to minimize strokes.
The Lothian Birth Cohort studies (there are two) were originally a slightly sinister attempt to map out the intelligence (or lack of it) in Scottish children during the 30s and 40s. The data were repurposed, and the subjects traced, to investigate how cognitive function changes with age. Almost as an afterthought, researchers have also correlated cholesterol markers for cancer, CVD and stroke.
Buried in this thesis, compiled by a true believer in the diet-heart hypothesis, is a set of figures that ought to register as a seismic event in medical history:
pdfs.semanticscholar.org/b3...
The important paper here starts on p161. Refer to the chart on p165, which shows total cholesterol correlating with various age-related diseases: stroke, CVD, and hypertension.
Have a look at the 'stroke' row, in which older people with low cholesterol have had a whopping 40% incidence of stroke, whereas those with "high" cholesterol (ie., normal, unmodified cholesterol) have had a 1% incidence. 1% incidence is about as close as you get in real life to zero: by way of comparison, the lifetime risk of a non-smoker getting lung cancer is about 5%. The CVD line is not quite as impressive, but still pretty dramatic: about 15% incidence in the mid/high TC groups, compared to 40% in the low TC group.
Now, the current bar for having 'high cholesterol', and being put on statins, is 5mmol/L - that is, at the dividing line between the 'low' and 'mid' groups in this chart. Note that many of those with cholesterol lower than 5mmol/L are in fact taking statins. Since statins very reliably reduce total cholesterol, we can infer that they have low cholesterol because they are taking statins. We can further infer that, if you don't take statins, your normal TC hovers somewhere around 6mmol/L, plus or minus, at age 70.
The author remarks, without any apparent sense of irony, that:
"In the current sample, the low-TC group had the highest prevalence not only of CVD but stroke, hypertension, statin use, and high BMI, and therefore the most likely group to have made dietary modifications as part of a health management program to reduce weight and improve overall health."
Translation: following the standard health advice, and taking statins, might be making you fat and ill. My goodness. It's another of those paradoxes!
You'd think somebody would have picked up on this paper, but it's actually quite hard to find. It's buried there in Dr Corley's PhD thesis, and in the five years since publication has been cited only a dozen times or so, as far as I can figure out. Yet here we apparently have a population of older people who do not get strokes ... and bear in mind that 'stroke' describes at least two distinct disease processes. Isn't this important? Shouldn't the NHS be taking note? Should they not, at least, reconsider the policy of handing out statins to 70-year-olds in view of that 40% incidence of strokes in a group with low cholesterol, and a minimum background level of strokes in the other groups?
I suppose the statin cheerleaders will say: "Ah but. You're looking at a single data point here. Perhaps those people in the low-cholesterol group may have been at high risk for other reasons, and would have all been dead by now if we hadn't prescribed them statins. 40% incidence is better than 100% incidence".
Well, maybe so. Except that the theoretical premise for taking statins is that high cholesterol leads to strokes and CVD, so if that defence is true, it suggests that the protective effect of statins (assuming it exists) has nothing to do with cholesterol reduction. More research, as they say, is needed. But since the response to this paper from the research community has been a big ol' ball of tumbleweed bouncing gently around the campuses, I'm not holding my breath.
