Dementia risk increased by high or levels of 'good' cholesterol, study claims
Too high or too low levels of good cholesterol could lead to a higher risk of dementia, a new study has found.
Over one in 10 adults in the US over the age of 65 have dementia. Although most patients have Alzheimer's there are other less common types including Frontotemporal dementia which Hollywood star Bruce Willis has been diagnosed with.
The field of study around the brain destroying disease has come along a huge way in the last 20 years but there is still a lot more that needs to be done. The new study by The American Academy of Neurology has found that having either too low or high levels of good cholesterol is linked to a small increased risk of dementia in older adults.
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Cholesterol, a fatty substance found in the bloodstream, is split into two categories - high-density lipoprotein (HDL) which is good and low-density lipoprotein (LDL) - which is bad. The team of boffins behind the study looked at over 184,000 volunteers over nine years with an average age of 70 who did not have dementia at the beginning of the study. They found a slight association between bad cholesterol and risk of the neurological disease.
Dr Michael Mosley shares exercise that can cut cholesterol and blood pressure“Previous studies on this topic have been inconclusive and this study is especially informative because of the large number of participants and long follow-up,” said study author Maria Glymour, ScD, of Boston University. “This information allowed us to study the links with dementia across the range of cholesterol levels and achieve precise estimates even for people with cholesterol levels that are quite high or quite low.”
Good cholesterol, also called HDL cholesterol, is found in food like avocados, nuts and oily fish. Bad cholesterol, also called LDL cholesterol, is found in red meat, dairy and fried foods. High levels of bad cholesterol, also pose risks for serious heart conditions like strokes and heart attack.
In contrast, good cholesterol removes excess bad cholesterol from the blood vessels and other tissues and returns it to the liver to be recycled or removed from the body. It also has an anti-inflammatory effect, which helps protect the artery walls against bad cholesterol build up.
The study included 184,367 people who completed a health survey and had their cholesterol measured an average of 2.5 times in the following two years. They were then followed via electronic health records for an average of nine years and during that time 25,214 people developed dementia.
Participants were divided into five groups based on their HDL cholesterol levels. Those with the highest levels of HDL cholesterol had a 15 per cent higher rate of dementia compared to those in the middle group. Those with the lowest levels had a 7 per cent higher rate of dementia compared to people in the middle group.
Scientists were sure to take into account other factors that could affect the risk of dementia, such as alcohol use, high , cardiovascular disease and diabetes.
“The elevation in dementia risk with both high and low levels of HDL cholesterol was unexpected, but these increases are small, and their clinical significance is uncertain,” Dr Glymour said. “In contrast, we found no association between LDL cholesterol and dementia risk in the overall study cohort.
"Our results add to evidence that HDL cholesterol has similarly complex associations with dementia as with heart disease and cancer.”