Too high or too low HDL (“good”) cholesterol linked to slightly increased dementia risk

Is “good” cholesterol always good for you? A recent study showed a link between HDL (“good”) cholesterol and increased dementia rate among people aged 70 and older.  Published in the medical journal of the American Academy of Neurology, the study revealed a modest association between high and low levels of HDL cholesterol and increased occurrences of dementia. 

By Alzheimer's Prevention Bulletin

A study of nearly 185,000 people with an average age of 70 showed that having high or low levels of high-density lipoprotein (HDL) cholesterol is tied to an increased risk of dementia.  Commonly called “good cholesterol,” the study showed a modest association exists between high or low levels of HDL and dementia, while LDL (“bad”) cholesterol was not linked to dementia risk.

The study took place in within Kaiser Permanente in Northern California, and results were published in October 2023 in Neurology, the medical journal of the American Academy of Neurology. Study participants included both men and women, all of whom volunteered to participate.

“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,” said study author, Maria Glymour, ScD, in a separate interview.  “Our results add to evidence that HDL cholesterol has similarly complex associations with dementia as with heart disease and cancer.”  

Jeremy Pruzin, MD, a neurologist at Banner Alzheimer’s Institute in Phoenix, AZ also found some of the study results unanticipated. “The finding that high levels of HDL may increase dementia risk was somewhat surprising,” he said. “What the study suggests is that a middle ground, a ‘goldilocks’ range of HDL that is not too high or not too low, is what may lower dementia risk.” 

 “The relationship of lipids to dementia is complex and hard to tease apart. This large study reiterates that point but does well in contributing to understanding how LDL and HDL contributes to dementia risk,” Dr. Pruzin added.

Key findings of the study included:

1. Higher HDL was linked to a higher dementia rate.
   The study found that people with the highest levels of good cholesterol had a 15% higher rate of dementia compared to those with average HDL levels. 
   
   
2. Low HDL levels were also associated with a higher dementia rate.
   People with low levels of good cholesterol also had a higher dementia rate than those with average HDL levels.  However, people with lower HDL levels had a lower rate of dementia at 7% than those with the highest HDL levels.
   
   
3. No association was found between average good cholesterol levels and dementia.
   Healthy levels of HDL are different for men and women.  For men, healthy levels are above 40 milligrams per deciliter (mg/dL); for women, HDL should be above 50mg/dL.  The average good cholesterol level among participants in this study was 53.7 mg/dL.
   
   
4. LDL cholesterol had little association with incident dementia.
   Bad cholesterol is clinically known as low-density lipoprotein or LDL.

While he discourages an overreaction to this “large and very well-done study,” Dr. Pruzin said that the study, “does support the well-known fact that paying attention to our cardiovascular risk factors like hypertension, diabetes, and cholesterol is important if we want to lower our risk for dementia.”

Noting that more and more data suggests that HDL is the more important marker as opposed to LDL, Dr. Pruzin advises, “If someone’s HDL is very low, this is both a risk for negative cardiovascular outcomes and dementia and should be discussed with their primary care doctor.”

More research is needed on the association of high or low HDL with risk of dementia, especially as it relates to different age groups and ethnicities. 

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