Fluctuating blood lipid levels linked with higher risk of Alzheimer’s disease, study finds

By Kristen Rogers, CNN

(CNN) — The fact that having high cholesterol can cause health problems is well known. But a total cholesterol level that fluctuates a lot — either up or down within a five-year period — might also be problematic by raising the risk of later dementia, a new study found.

“This study adds to a growing body of evidence showing that addressing certain modifiable risk factors and promoting healthy behaviors can reduce the risk of cognitive decline, possibly reduce the risk of dementia, and protect cognitive health,” said Christopher Weber, director of global science initiatives at the Alzheimer’s Association, via email. He was not involved in the study.

Among nearly 11,700 adults with an average age of 71, researchers found that those with the most variability in their total cholesterol level had a 19% higher risk of developing Alzheimer’s disease or Alzheimer’s disease-related dementia, also called ADRD, within 12 years. The study published Wednesday in the journal Neurology.

The findings suggest that “prevention strategies for Alzheimer’s and related dementias are urgently needed,” said study author Suzette J. Bielinski, a genetic epidemiologist at the Mayo Clinic in Minnesota, in a news release.

“Routine screenings for cholesterol and triglyceride levels are commonly done as part of standard medical care,” Bielinski added. “Fluctuations in these results over time could potentially help us identify who is at greater risk for dementia, help us understand mechanisms for the development of dementia and ultimately determine whether leveling out these fluctuations could play a role in reducing dementia risk.”

An abnormally high level of lipids in the blood — such as cholesterol or triglycerides — has been linked with Alzheimer’s and other dementias in past studies. Previous studies have also found that variability of total cholesterol levels over time is associated with Alzheimer’s disease and related dementias, but how the risk differs among specific types of cholesterol hasn’t been fully understood, according to the new study. Lipid variability, as the authors defined, refers to any change in an individual’s lipid levels over time regardless of whether they increased or decreased.

The authors sought to better understand these relationships between multiple lipid types and Alzheimer’s disease or related dementias by looking at health records of adults who were from Minnesota, predominantly White and hadn’t been diagnosed with Alzheimer’s disease or ADRDs.

Participants’ lipid levels were gathered on at least three different days in the five years before the start of the study on January 1, 2006, and then researchers tracked whether participants developed Alzheimer’s disease or related dementias through 2018.

In addition to total cholesterol, the study tracked triglycerides, a type of fat that comes from butter and oils; low-density lipoprotein cholesterol, also known as LDL or “bad” cholesterol; and high-density lipoprotein cholesterol, known as HDL or ‘good’ cholesterol.  

In the Neurology study, variations in LDL and HDL cholesterol weren’t associated with higher risk for Alzheimer’s disease or related dementias. But those with the most fluctuation in triglyceride levels had a 23% higher risk compared with participants who had experienced the least variation.

Lipids and neurodegenerative disease

The authors found a link, but not a causal relationship, between fluctuating levels of cholesterol and triglycerides and risk of Alzheimer’s disease and related dementias.

Additionally, the study had a few limitations: The authors looked at Alzheimer’s disease and related dementias as a whole, not differentiating between the types of dementia. They also didn’t know whether any participants had undiagnosed Alzheimer’s or related dementias at the beginning of the study, which could theoretically cause changes in diet and activity, and therefore lipid variation. The authors also didn’t have data on what participants’ lipid levels were in the years between 2006 and 2018.

“Further studies looking at the changes over time for this relationship are needed in order to confirm our results and potentially consider preventative strategies,” Bielinski said.

Exactly how varying lipid levels and risk for Alzheimer’s or related dementias are related remains unclear, Bielinski said. Experts do have theories on the mechanics, though.

“Cholesterol fluctuations can negatively impact the brain’s vascular health,” Weber said, “and contribute to an increased risk of developing cognitive decline and dementia, including Alzheimer’s disease.”

Fluctuation of total cholesterol could lead to instability of plaque in the arteries, raising risk of damage to the brain and its blood vessels, according to the study. This could increase the risk of experiencing cognitive impairment and Alzheimer’s in later life, Weber said.

Managing blood lipid levels

The best ways to keep your lipid levels, brain function and heart health in check involve a few lifestyle adjustments, according to the Mayo Clinic and Weber — such as regularly exercising at least most days of the week; avoiding added sugar and refined carbohydrates, which can raise triglycerides; losing excess weight; choosing healthier fats such as those found in plants or salmon; and limiting alcohol.

If lifestyle changes aren’t enough, your doctor may prescribe medications or supplements that can help lower your cholesterol or triglycerides, such as statins, fibrates, fish oil or niacin.

“Always consult your doctor or healthcare provider if you are concerned about your cardiovascular health, cholesterol levels, or cognitive decline,” Weber said via email.

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