• Posted October 26, 2023

High Blood Triglycerides Could Help Ward Off Dementia

High triglycerides, widely known as an enemy of the aging heart, may not be as threatening to older adults' brains, new research suggests.

The study, of over 80,000 older adults, found those with triglycerides in the "high-normal" or moderately high range were less likely to develop dementia, versus their peers with lower triglyceride levels.

Over six years, 3% of older folks with the highest triglyceride levels developed dementia -- half the rate seen in the study group with the lowest triglycerides, at 6%.

Experts stressed some important caveats around the findings, published Oct. 25 in the journal Neurology.

The main one is the study doesn't prove that triglycerides somehow shield the aging brain.

"This particular study is not enough to derive recommendations and claim with certainty that changing triglyceride levels will affect future dementia risk," said Dr. Nikolaos Scarmeas, a neurologist at Columbia University in New York City.

The findings are still important, though, said Scarmeas, who cowrote an editorial published with the study.

He noted that blood "lipids" -- cholesterol and triglycerides -- can be easily modified with diet or medication. So, if further studies show they directly affect dementia development, that would offer one way to lower the risk.

Zhen Zhou, a research fellow at Monash University in Australia, led the study. She said there could be various explanations for why low triglycerides were linked to higher dementia risk.

In older people, Zhou said, low triglycerides may be related to weight loss, malnutrition, health conditions or frailty.

That's distinct, she noted, from the situation during middle age, when high triglycerides may feed the development of heart disease. Older adults with relatively high triglycerides may be better nourished, or have fewer health conditions, than their peers with low levels.

In general, a triglyceride level below 150 is considered healthy for adults. Numbers between 150 and 199 are borderline-high (or high-normal), while levels of 200 or more are considered high.

Some past studies have found a similar "inverse" relationship between older adults' triglycerides and their dementia risk: That is, the higher the blood lipid, the lower the dementia risk. But some other studies have found no link.

For the new study, Zhou and her colleagues wanted to dig deeper. They pulled data from two large research projects that involved older adults from Australia, the United States and United Kingdom. All were free of dementia, as well as heart disease or stroke, at the study's outset.

One study followed over 18,000 older adults for an average of six years. During that time, 823 were diagnosed with dementia.

When the researchers looked at things by triglyceride level, there was a clear pattern: Dementia risk was highest in the 10% of seniors with the lowest triglycerides. (Their triglycerides were below 62.)

At the other end of the spectrum were the 10% of seniors with the highest triglycerides (above 186).

The rest of the study group, whose triglycerides ranged from 62 to 186, had dementia rates that were somewhere in between, at 4% to 5%.

The second study included over 68,000 older British adults who were followed for 12 years. Again, dementia risk declined as participants' triglyceride rates rose.

The researchers were able to account for a number of other factors -- such as people's cholesterol levels and blood pressure, smoking and drinking habits, and body weight.

Even then, the triglyceride-dementia link remained intact: Seniors with the highest triglycerides in the first study had a 36% lower risk of dementia, versus those with the lowest triglycerides.

Zhou stressed that even among older adults with the highest triglycerides, very few had severely elevated levels -- the kind that could harm the heart or pancreas and are often treated with medication.

Instead, she said, the findings mainly pertain to older folks with triglycerides in the high-normal or "slightly" high range.

Beyond that, it's not clear what study participants' lifelong triglyceride levels were, or how those levels at younger ages might relate to dementia risk years later.

"The impact of triglycerides on dementia risk can change depending on when it's measured in a person's life," Zhou said. "A reading taken in one's 40s might relate differently to dementia risk than a reading taken in one's 70s."

If triglycerides do somehow contribute to dementia risk, the reasons remain unclear.

One past study found that older adults with low levels of certain triglyceride components had more atrophy in brain regions involved in memory, Zhou's team pointed out. But again, that doesn't prove cause-and-effect.

More Information

The Alzheimer's Association has advice on supporting brain health.

SOURCES: Zhen Zhou, PhD, research fellow, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia; Nikolaos Scarmeas, MD, MS, associate professor, clinical neurology, Columbia University Irving Medical Center, New York City; Neurology, Oct. 25, 2023, online