It’s been described as the silent killer for good reason. With no outward signs or symptoms, cholesterol (a waxy, fatty substance present in the blood) can slowly build up, clogging arteries and leading to potentially fatal heart attacks and strokes.
Six in ten adults in the UK are thought to have abnormally high levels and most are unaware of it.
Of particular concern is that prevalence has risen dramatically since the pandemic, after decades of decline. This is attributed to a drop in the number of people invited for NHS health checks, which measure cholesterol and are supposed to be carried out on all people aged between 40 and 74 every five years.
But decades of scientific research have revealed that there is even more cause for alarm. High cholesterol, and in particular a type known as low-density lipoprotein (LDL), is integral to the cascade of problems that eventually lead to dementia.
Studies that have followed millions of people for decades have found that every small increase in the amount of LDL circulating in the blood is associated with an 8% increased risk of developing dementia in old age. And having persistently high levels can increase the risk by 33%.
Significantly, the risk was highest in middle age, between 40 and 65 years, suggesting that high cholesterol at this stage could trigger a range of problems that result in dementia.
It is certainly a dramatic advance, but it offers a huge opportunity to simultaneously tackle heart disease and one of our most feared brain diseases.
Doctors say it’s never too late to do something about high cholesterol
Not only can high cholesterol be easily and inexpensively detected in doctors’ offices or with self-testing kits, but there are also extremely effective ways to lower it.
Several reviews of the best evidence have concluded that statins (cholesterol-lowering drugs) can reduce the risk of dementia, and particularly Alzheimer’s, by up to a third.
Even eliminating unhealthy foods that contain saturated fats, which are linked to high cholesterol, could reduce your risk.
A Danish study, which followed people for an average of 58 years, found that those who did not follow healthy dietary guidelines were more likely to have high LDL and develop some forms of dementia, compared to those who did eat a balanced, healthy diet.
“Making simple lifestyle changes to lower cholesterol could have a huge impact on brain function and will inevitably delay or even completely prevent the onset of dementia and heart disease later in life,” says Dr Osman Shabir, an expert in the impact of cardiovascular disease on the brain at the University of Sheffield who works with Alzheimer’s Research UK and the British Heart Foundation.
“If you have high cholesterol, you can do something about it. Even if you are in your 50s or 60s, you can modify these risk factors. It’s never too late.”
The mechanism linking high cholesterol to vascular dementia, a form of the disease that occurs when blood flow to the brain is reduced, is well established. As we age, levels of cholesterol (which is produced primarily in the liver but is also linked to a high-fat diet) rise in the blood.
Doctors are generally most concerned about levels of LDL (balls of fat and protein that carry cholesterol from the liver into the bloodstream) and are often called “bad” cholesterol because they can clog arteries.
The body also produces high-density lipoprotein (HDL), often called “good” cholesterol because it carries cholesterol from the arteries to the liver, where it is broken down and excreted.
Over time, LDL can build up on artery walls and harden them, which can lead to clots forming. These can break off and damage the blood-brain barrier, a delicate layer of cells designed to protect the brain from clots and toxins.
“This allows clots to enter the brain and cause strokes, reducing the blood supply to parts of the brain and eventually leading to vascular dementia,” says Dr Owen Peters of the UK Dementia Research Institute.
And this relationship between cholesterol and Alzheimer’s is more complicated.
Alzheimer’s develops differently than vascular dementia and is thought to be linked to the buildup in the brain of toxic plaques called amyloid and protein tangles called tau. Some research has found that having heart disease (including high cholesterol in the body) triples the amount of amyloid in the brain.
Dr Shabir says: “Brain cells are no longer able to do their job properly, which is to remove amyloid, so more of it builds up faster and faster, which can increase the risk of Alzheimer’s.”
The relationship between genetic risk factors for Alzheimer’s and brain cholesterol levels is also being investigated.
The brain produces its own cholesterol, which is a key component of brain cell structure and communication between cells. But people who carry two copies of a gene called APOE4 — who are eight times more likely to develop Alzheimer’s — have higher volumes of amyloid in their brains and also more LDL cholesterol, Dr. Peters says.
About two percent of the population has two copies of this gene, which they inherit from their parents.
“It’s not clear whether this is related to the fact that cholesterol from the body crosses a leaky blood-brain barrier or to some other process that occurs within the brain,” he says. “The APOE4 gene is involved in cholesterol transport in the brain, but we don’t know how it’s all related. The relationship is very complicated, but it seems clear that cholesterol has some kind of role in Alzheimer’s.”
People with a different gene, APOE2, are protected against Alzheimer’s and tend to have lower cholesterol levels, adding to evidence that cholesterol appears to be important.
Regardless, studies appear to show that taking statins in middle age can significantly reduce the risk of dementia.
These once-daily pills, which reduce the amount of LDL produced by the liver, can lower levels by up to 50 percent. They also reduce the risk of blood clots forming.
One analysis found that people who used statins had a 32 percent lower risk of Alzheimer’s disease and a 20 percent lower risk of vascular dementia, compared with people with untreated high cholesterol.
Some experts advise caution, as these studies are only observational (showing an association over time) and some doubts remain about the theory.
An analysis of the evidence by the respected Cochrane group of researchers concluded that statins given to people at risk of vascular disease did not prevent cognitive decline or dementia. However, the studies the team analysed gave statins to people later in life, when damage caused by high cholesterol may have already set in motion the biological processes that lead to dementia. In other words, it may have been too late.
Despite gaps in knowledge, experts agree that maintaining a healthy cholesterol level can only have benefits for overall well-being, whether by using statins, changing diet or becoming more active.
NHS guidelines recommend reducing consumption of fatty foods, particularly those containing saturated fats found in butter, cheese, mince pies, fatty meats, cakes and biscuits.
Instead, eat more oily fish (such as mackerel and salmon), brown rice, whole-grain bread and pasta, nuts and seeds, and fruits and vegetables.
An analysis of the evidence found that diets rich in tomatoes, flax seeds, almonds, soy protein, avocados and high-fiber foods or whole grains caused “small to moderate” reductions in LDL cholesterol. However, unfiltered coffee and sugar caused an increase.
“Adopting heart-healthy habits can have a profound effect on heart health, but also on brain health,” says Ioanna Tzoulaki, professor of chronic disease epidemiology at Imperial College London. “This could include a healthy diet, getting more exercise and taking statins, if necessary, to lower cholesterol.”
I am taking statins after my parents died of dementia.
Shelle Luscombe, 53, pictured above, ignored her own health for years as she cared for her ailing parents.
His father, Ian, suffered from a form of dementia related to Parkinson’s disease. His mother, Sue, battled Alzheimer’s and vascular dementia.
But after they both died in the mid-70s, Shelle, who lives on the West Sussex coast, had her cholesterol tested and “panicked” when her level was dangerously high. Her GP prescribed her statins and she changed her diet.
“It was a wake-up call,” says Shelle, who works in the music and events industry. “I have several friends whose parents have dementia or died from it, and we all feel the same way – the more information we have about what we can do to prevent this happening to us, the more positive it is. It doesn’t have to be something that just happens to us.”
The Government must do more to ensure all adults take their NHS health check, according to Alzheimer’s Research UK (ARUK).
The 30-minute appointment, which should be offered to everyone aged 40 to 74 every five years, includes a series of tests to detect early signs of potentially life-threatening diseases.
Patients typically have their height, weight and waist circumference measured, a blood pressure test and a finger-prick blood test to check their cholesterol.
The doctor will then explain to the patient his or her risk of developing a serious illness, such as heart disease, stroke, or kidney disease.
However, the data shows that only 56 per cent of men and 61 per cent of women take up the offer of an NHS health check. The number of people coming forward for their check-up, which is similar to a body MOT, has also fallen over the past three decades. In 1998, 66 per cent of men and 67 per cent of women had the tests.
Following the results of the Lancet Commission’s research, the Health Check cholesterol test could now also be a key means of warning about the risk of developing dementia.
“It is crucial to ensure more people attend these vital appointments,” says Samantha Benham-Hermetz, ARUK chief executive.
‘It’s a double win, as keeping cholesterol at healthy levels not only reduces the risk of dementia, but also diabetes and heart problems.’