The findings of a major study on heart disease in women should shift the way doctors look at prevention.
The study is the US-based Women’s Health Study, run from the Brigham and Women’s Hospital and Harvard Medical School in Boston. The research team aimed to identify the major heart disease risk factors, using data collected over 21 years from 28,000 participants.
All were over 45 and had no history of heart disease when the study began. The research split them into four age groups: under 55, 55 to under 65, 65 to under 75, and over 75.
The good news was that after 21 years the vast majority (94.5%) didn’t have the disease. (Of the 5.5% who did, most — 2.3% — were in the 65 to under 75 age group.)
Given prevention has, for decades, been about lowering cholesterol and blood pressure, the key risk factors that showed up might come as a surprise.
In order, the top three were: type 2 diabetes, metabolic syndrome and being a current smoker.
We’ve long known smoking is a risk factor, but diabetes carried more than twice the risk of smoking. Diabetes appeared to be especially dangerous for the two younger groups (i.e. under 55, and 55 to under 65). Having it increased the risk of heart disease more than ten-fold. That’s huge.
Diabetic women in the 65 to under 75 group had 4.5 times the risk, and in women over 75 diabetes increased the risk 3.5 times.
The second highest risk factor, metabolic syndrome, is a cluster of five conditions: a big waist, high triglycerides, high blood pressure, high blood sugar and low HDL (‘good’ cholesterol). We’re considered to have the syndrome if we have any three of the five.
Metabolic syndrome is also linked with insulin resistance, which occurs when our blood sugar stays too high for too long. Our pancreas produces the hormone insulin to help our cells use sugar for fuel, but if there’s a continuous overload of sugar, our cells stop responding to the insulin. The pancreas then pumps out more and more, so we end up with high levels of both blood sugar and insulin.
Metabolic syndrome and insulin resistance are precursors to diabetes.
Triglycerides, which might be the least understood of the five metabolic syndrome conditions, are a type of fat in the blood. Since they’re boosted by a high carbohydrate intake, they go hand-in-hand with high blood sugar and insulin resistance.
Clearly a lot of these symptoms overlap, and the next three highest risk factors were three of the five: i.e. blood pressure, triglycerides, and BMI (which was used to identify obesity).
Total cholesterol and LDL (‘bad’) cholesterol came in at number 7 and number 8.
If we needed more evidence that cholesterol isn’t the be-all-and-end-all of heart disease this is surely it.
A family history of early heart disease and a sedentary lifestyle are part of the picture too, but the stark message is that to lower our risk of heart disease we need to reduce our insulin levels and our risk of diabetes.
Insulin resistance has also been implicated in other chronic diseases such as Alzheimer’s.
While we should never put all our eggs in the basket of one study, the results found here aren’t new.
But they reinforce that demonising foods like eggs or full-fat dairy, focusing on saturated fat intake, and regarding LDL cholesterol as a central marker of heart disease risk are wide of the mark, at least in women.
Moreover, statins are known to increase the risk of diabetes among women.
It’s also worth noting that LDL particles come in different sizes. Some are big, fluffy and benign while others are small and more dangerous. So it’s important to know what type we’re talking about.
Individual differences notwithstanding, we reduce insulin levels by cutting back on sugars and starches, especially the refined ones. Protein, fibre and healthy fat help to stabilise insulin.
But when some of us make this dietary shift and include more (healthy) fat in our diet, our LDL levels increase. While that often creates alarm, these are the big particles, which shouldn’t be a cause for concern.
The knowledge that the focus for heart disease prevention ought to be insulin reduction and not LDL reduction should see a big turnaround in the medical world’s approach.
Will it? Watch this space. But maybe don’t hold your breath.