Stable Blood Sugar Levels Could Reduce Dementia Risk in Older Adults With Diabetes

By Jennifer Sweenie

Maintaining optimal blood sugar levels could hold the key to reducing the risk of developing dementia later in life, according to recent research. A study published in JAMA Network Open in August found that a stable hemoglobin A1c (HbA1c) may be associated with a reduced risk of dementia in older Type 2 diabetes patients.

The HbA1c is a three-month average of the amount of glucose in the blood, expressed as a percentage. The measurement is used to evaluate a person’s blood sugar control.

The prevalence of dementia is expected to rise in the coming years, placing a significant burden on health care systems and caregivers. This emerging evidence linking stable blood sugar levels with a reduced risk of dementia underscores the importance of proactive measures to support cognitive health.

Identifying risk factors that are modifiable, such as blood sugar levels, could be paramount in developing effective preventive strategies for Alzheimer’s disease and related dementias.

Study Findings

The study shows that extreme glucose levels measured by the average HbA1c are associated with an increase in dementia incidence. Glucose levels persistently below a set target range may lead to changes associated with a heightened risk of developing Alzheimer’s disease and related dementias, and blood sugar stability is associated with a reduced dementia occurrence.

Dr. Paul R. Conlin, an author of the study, and chief of the medical service at VA Boston Healthcare System, summarized the findings of the study in an email to The Epoch Times, “Among older adults with diabetes, maintaining stable HbA1c levels within patient-specific ranges is associated with a lower risk of Alzheimer’s disease and related dementias. Dementia risks are particularly increased when HbA1c levels are mostly below target ranges.”

The cohort study included 374,021 older veterans with diabetes. The veterans were primarily males 65 years or older, with a mean age of 73.2. The data assessed was collected from 2004 to 2018. Participants were required to have at least four HbA1c tests during a baseline of three years to determine their HbA1c time in range (TIR).

“We calculate the percentage of time over a 3-year period that a patient’s HbA1c levels are within their target range,” Conlin said.

Eleven percent of the participants in the sample had developed Alzheimer’s and related dementias during their follow-up of up to ten years. There was also an association with the direction of out-of-range levels—a greater time below the range (60 percent or more) was linked to a significant risk.

“Ongoing diabetes care is important to reduce its complications, such as heart disease, kidney disease and dementia. We’re fortunate that Veterans provided us with this unique opportunity to study these health problems,” noted Conlin.

HbA1c Time-In-Range

HbA1c TIR measures the percentage of time that a person’s blood sugar level spends within a target range, typically expressed as a percentage of 24 hours. For example, a patient may have a target of an HbA1c of 6 to 7 percent with a time in range of 60 percent or greater.

This means that, ideally, their blood consists of 6 to 7 percent glucose for at least 60 percent of the time. The sum of the time their HbA1c is in range, above range, and below range will equal 100 percent. This measure offers a more comprehensive view of a patient’s blood sugar regulation compared to the HbA1c.

“We found that HbA1c TIR provides additional risk information beyond that contained in single HbA1c tests,” said Conlin.

A person’s target range is patient-specific and based on their current health status. Conlin clarifies that lower HbA1c target ranges are appropriate for those in good health, and higher ranges are appropriate for those experiencing major health challenges.

Higher HbA1c TIR, or less HbA1c variability, is preferred,” he said.

The Link Between Blood Sugar and Dementia

Alzheimer’s disease has been coined Type 3 diabetes in recent years due to its shared mechanisms with diabetes and insulin resistance that are associated with cognitive decline. A meta-analysis published in May in Diabetology & Metabolic Syndrome ultimately concluded that, though little is understood about this relationship,  there is a “robust link between diabetes and the onset of dementia.” Notably when the diabetes duration is under five years or there is hypoglycemia.

A meta-analysis published in Diabetes Research and Clinical Practice in 2022 found that, again, although the data is limited, there is an association between prolonged blood sugar variations and an increased risk of dementia. In addition to varying blood sugar levels, a history of severe episodes of hypoglycemia is also associated with an increased risk of Alzheimer’s and related dementias in those with Type 2 diabetes.

Research published in 2022 in the Journal of Alzheimer’s Disease determined that chronic hyperglycemia, even in those who are only at a pre-diabetes level, is significantly associated with an increased risk of developing Alzheimer’s disease. A cohort study published in JAMA Network in 2021 found that the onset of Type 2 diabetes at a younger age is significantly associated with a higher risk of dementia.

Conlin says that there are several mechanisms presumed to increase the risk of Alzheimer’s and related dementias in people with diabetes.

“For example, diabetes leads to vascular and nerve damage, and its treatment may result in low blood sugar (i.e., hypoglycemia), each of which can alter cognitive function,” he notes.

One possible explanation for the link between blood sugar levels and dementia is the effect of glucose on the brain. A systematic review published in Neuroscience & Biobehavioral Reviews in 2022 notes that fluctuations in blood sugar levels can affect cognitive performance in healthy individuals.

“Glucose is also an important fuel for the brain, and glucose fluctuations over time may disrupt the brain’s use or availability of this energy source,” said Conlin.

Stable Blood Sugar May Prevent Dementia

The recent JAMA study reported that the incidence of Alzheimer’s disease and related dementias is higher in those with diabetes. For those without diabetes seeking to mitigate their prospects of cognitive decline, Conlin suggests that a more important risk-reducing strategy is to prevent the development of diabetes in the first place.

“We don’t know the mechanisms for dementia risk in patients with diabetes, so we can’t extrapolate these findings to people without diabetes,” Conlin pointed out. Further research on the connection between blood sugar and dementia is warranted.

“We found a significant association between low HbA1c TIR and dementia risk, but this doesn’t define a cause-and-effect relationship,” he added.

“An important next step is to see if increasing HbA1c TIR prospectively reduces the risk of dementia,” said Conlin.