World first: risk of dementia linked to high cholesterol

Scientists at the Heart Research Institute (HRI) have made a world-first breakthrough discovery, linking high cholesterol with an increased risk of dementia for the first time.

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

The research led by HRI's Dr Ashish Misra, Unit Leader of the Atherosclerosis and Vascular Remodelling team, analysed the data of 17 global studies, involving more than a million patients under the age of 65.

Dr Misra said the findings could be a game changer in reducing our risk of cognitive decline as well as improving our overall health.

“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.

If there's too much cholesterol in the blood, the cholesterol can form 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.”

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

Up to 40 per cent 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 per cent of MCI patients progress to dementia within five years.

“It’s very exciting to know that if we can classify someone as high risk by 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.

Dementia is a neurodegenerative disease that causes the gradual impairment of brain function, which could 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. That equates to 15 Australians in every 1,000, and increases to 84 people with dementia per 1,000 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.

Header image: Dr Ashish Misra