Heart Research Institute warns of link between high cholesterol and dementia

It's the first time a direct link has been found between what we eat and cognitive decline.

The research could see doctors soon able to calculate a person's risk of dementia by testing their cholesterol levels through an inexpensive and easy blood test.

The research by the Sydney-based Heart Research Institute could be a game changer in reducing the risk of cognitive decline as well as improving overall health.

Led by HRI's Dr Ashish Misra, the researchers analysed the data of 17 global studies, involving more than a million patients under the age of 65.

"This is a really exciting discovery because we've found the association between cholesterol and dementia. Until now we haven't known high cholesterol was a risk factor for dementia, but we've found a link: "bad" cholesterol aggregates a protein called tau between neurons, which cross the blood-brain barrier, and can lead to dementia," Dr Misra said.

Cholesterol is a type of fat (or lipid) that plays an important role in the body, helping to make hormones, Vitamin D, and substances that aid in digestion, however too much "bad" cholesterol from a high fat diet or dyslipidaemia, where there's an imbalance of lipid levels in the blood, can be deadly.

Too much cholesterol in the blood can lead to the formation of plaques that collect on the artery walls, causing them to become narrow and even blocking them, reducing blood flow and increasing the risk of a stroke.

Experts say once plaque develops on the arteries it is near impossible to dissolve completely.

"Unfortunately, there's no magic drug to get rid of the plaque on your arteries. We need to learn to live with it and help it dissolve over time through improved diet and a healthy lifestyle," said Dr Misra.

"It's very exciting to know that if we can classify someone as high riskby checking their blood work for high cholesterol in their 50s, then we can look at their diet as a way of managing and even reducing their risk of dementia.

"Better still, it's a low-cost intervention. It's checked with a blood test so it's easy to detect," Dr Misra said.

Dr Misra said this discovery is not only about extending a person's life but giving them a better quality of life.

"Living longer is not important if you are not living healthy," he said.

Up to 40 percent of a person's dementia risk can be attributed to modifiable risk factors, with evidence that the effects of dementia begin 10 to 20 years before clinical symptoms emerge.

"Mild cognitive impairment (MCI) is considered to be an 'at-risk' stage for dementia, with the decline in cognitive function beyond what is expected for normal aging. More than 50 percent of MCI patients progress to dementia within five years."

Dementia is a neurodegenerative disease which causes the gradual impairment of brain function, which can impact a person's memory, speech, cognition (thought), personality, behaviour, and mobility.

The Australian Institute of Health and Welfare estimates there were between 401,300 and 487,500 Australians living with dementia in 2022 - 15 Australians in every 1000, and increases to 84 people with dementia per 1000 for Australians aged 65 and over.

With an ageing and growing population, that figure is projected to more than double by 2058 to 849,300 people.

"There is substantial interest in identifying early to midlife interventions that may prevent lifetime occurrence of dementia," he said.

Dr Misra said the next step is to find out how to reduce and treat the cholesterol (lipids) and compare the results with a drop in cognitive decline.