Dementia risk linked to blood sugar, cholesterol levels at 35

• Researchers recently investigated the link between cardiovascular measures and Alzheimer’s disease.
• They found that low high-density lipoprotein (HDL or “good” cholesterol), high triglycerides, and blood glucose levels from age 35 are associated with increased Alzheimer’s risk.
• The authors conclude that early intervention to maintain healthy HDL, triglyceride, and glucose levels may lower Alzheimer’s risk.

Alzheimer’s disease (AD) is the fifth leading cause of death among Americans age 65 and older. There are no proven ways to prevent or slow cognitive decline caused by AD.

Studies show that while vascular risk burden from age 55 predicts AD, whether or not this link is present in younger individuals is unknown.

Knowing how early this link begins could help researchers understand more about AD as a life-course disease.

Recently, researchers from Boston University investigated the relationship between AD and vascular measures using longitudinal data.

They found that low HDL cholesterol, high triglyceride levels, and high glucose levels in the blood from age 35 are linked to AD later in life.

The study appears in the journal Alzheimer’s and Dementia.

“Many people know high cholesterol is a risk factor for heart disease and other health conditions, but they don’t realize it’s a risk factor for dementia too,” Dr. Katy Bray, public engagement manager at Alzheimer’s Research UK, who was not involved in the study, told Medical News Today.

“To keep the brain healthy as we age, the best evidence is to eat a balanced diet, not smoke, drink within recommended guidelines, exercise regularly, and keep blood pressure and cholesterol in check.”

Data analysis

For the study, the researchers included data from 4,932 individuals who were a part of the Framingham Heart Study. Participants had an average age of 37 upon enrollment and underwent nine examinations every 4 years until the age of 70.

At each examination, researchers measured participants’:

• HDL and low-density lipoprotein (LDL or “good”)cholesterol
• blood glucose levels
• body mass index (BMI)
• systolic and diastolic blood pressure
• number of cigarettes smoked per day

From the second examination onward, the participants also underwent cognitive assessments to track the progression of cognitive decline.

After analyzing the data, the researchers found an inverse relationship between AD and HDL measured at the first, second, sixth, and seventh examinations.

The study also links AD to higher triglyceride levels at the first, second, fifth, sixth, and seventh examinations, independent of medication.

Meanwhile, high blood glucose was significantly linked to the development of AD at every exam.

The researchers also found no association between AD and LDL, BMI, smoking, or blood pressure at any examination.

Underlying mechanisms

MNT also spoke with Dr. Allison B. Reiss, an associate professor of medicine at NYU Long Island School of Medicine and a member of the Alzheimer’s Foundation of America’s Medical, Scientific, and Memory Screening Advisory Board. Dr. Reiss was not involved in this research.

“The brain is full of cholesterol and needs cholesterol to develop and produce nerve cells,” she explained.

“The balance and transport of cholesterol within the brain are carefully controlled, and lipids are very important in brain function. Most prominent of the lipid-related proteins in the brain is ApoE, a protein that transports lipids in the brain and elsewhere.”

“Some HDL particles contain ApoE (apoE-rich HDL), and this type of apoE-rich HDL is most concentrated in the brain. The quality and quantity of apoE-rich HDL may partially explain the Alzheimer’s disease-HDL link,” she continued.

Xiaoling Zhang, Ph.D., assistant professor of medicine and biostatistics at Boston University School of Medicine, one of the study’s authors, told MNT that improved blood flow in the brain might also explain some of their findings.

She explained that HDL could increase transportation and thus reduce the accumulation of amyloid-beta plaques, which are protein build-ups characteristic of AD.

When asked about the link between AD and glucose levels, Dr. Zhang said that higher glucose levels in the blood are linked to higher brain glucose concentrations and more severe plaques in AD brains.

“We know that the brain relies on glucose for energy, but excess glucose in the brain can undergo chemical reactions that make it damaging and inflammation-inducing. When glucose levels are high over extended periods, chronic neuroinflammation may result.”

– Dr. Reiss

“Another problem with high glucose is that it prompts the release of insulin to lower the glucose, and this can lead to wildly fluctuating sugar levels in the brain, which is very bad for nerve cells,” she explained.

The researchers conclude that early intervention to maintain healthy HDL, triglyceride, and glucose levels may lower AD risk.

However, they also note several limitations to their work. As their cohort was white, they say their findings may not translate to other demographics.

They further say that due to limitations in their study design, their results may not accurately reflect age-specific trends. Since the researchers did not take fasting blood samples at the first two examinations, their results may be slightly skewed.

When asked about the main practical takeaways from the study, Dr. Reiss said: “Eating less sugar and processed foods and exercising regularly are good for every organ and especially the brain and heart. Monitoring blood glucose and the lipid profile and watching HDL are great preventative measures.”

“We do not have drugs that raise HDL without causing a lot of side effects and, if the HDL is not of good quality, raising it is pointless. For now, the best way to support HDL levels is through exercise and physical activity,” she concluded.

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