Blood Sugar Spikes After Meals May Raise the Risk of Alzheimer’s Disease

A new study found that experiencing post-meal blood sugar spikes could potentially increase the risk of Alzheimer’s disease.

The research, published in the journal Diabetes, Obesity and Metabolism, adds to existing evidence suggesting that high blood sugar, also known as hyperglycemia, and insulin resistance—a condition in which cells don’t process sugar correctly—seem to play a role in cognitive decline.

The findings “highlight the critical importance of early identification and monitoring of metabolic abnormalities,” Arman Fesharaki-Zadeh, MD, PhD, an assistant professor of psychiatry and neurology at Yale School of Medicine, told Health.

While there is a well-established association between blood sugar spikes and Alzheimer’s, the specific nature of the relationship has remained fuzzy.

To gain insight into the link, researchers from the University of Liverpool and other institutions analyzed genetic data of 357,883 adults aged 40 to 69 enrolled in the U.K. Biobank, a biomedical database of adults in the United Kingdom. They specifically looked at fasting glucose, insulin, and blood sugar levels two hours after eating—all markers that indicate how the body processes sugar. Using a research technique called Mendelian randomization, they then investigated whether those markers were associated with dementia.

The team found that postprandial hyperglycemia—high blood sugar after a meal—was significantly associated with an increased risk of Alzheimer’s dementia.

Those with higher blood sugar levels after eating faced a 69% greater risk of Alzheimer’s disease, the researchers discovered. 

The study “could pave the way for new approaches to reduce dementia risk in people with diabetes,” noted study author Vicky Garfield, a senior lecturer in genetic epidemiology at the University of Liverpool, in a press release. However, she said the link first needs to be confirmed in other populations and ancestries.

Though blood sugar and brain health appear to be closely linked, the reasons why are poorly understood. Still, there are some theories, according to Marilyn Tan, MD, FACE, FACP, a double board-certified endocrinologist and internal medicine physician at Stanford Medicine.

Past research suggests that hyperglycemia increases amyloid beta accumulation in the brain, which has been linked with Alzheimer’s. Additionally, hyperglycemia may worsen oxidative stress, which can damage brain cells, trigger inflammation in the brain, and impair neuron and mitochondrial functioning, evidence suggests.

Plus, poorly-controlled diabetes and hyperglycemia are both associated with conditions that may contribute to cognitive decline, such as cardiac problems, including stroke and vascular dementia, and metabolic conditions such as obesity, hyperlipidemia, and hypertension.

“The underlying mechanisms likely involve widespread neurovascular dysfunction and systemic vascular compromise, affecting both peripheral organs and the brain, thereby increasing the risk of future cerebrovascular events, stroke, and dementia,” Fesharaki-Zadeh said.

Fesharaki-Zadeh said the findings highlight the importance of metabolic monitoring, which is typically done at an annual physical. At these appointments, a physician will analyze various metabolic markers, including your blood glucose, lipid profiles, and blood pressure. Depending on the results, doctors may recommend medications or lifestyle interventions.

Prevention is crucial. Many doctors recommend following the Mediterranean diet, exercising regularly, and cutting back on processed foods and added sugars.

These small tweaks are highly effective for improving glycemic control, Fesharaki-Zadeh said. “Implementing these measures will require a broader cultural shift toward metabolic health, with substantial preventive potential, including delaying or possibly preventing the onset of dementia,” he said.