On its own, diabetes is destructive, but excessive blood sugar levels are linked to the damage to various organs, including the brain. This article gives an idea about the correlation between diabetes and dementia which is important to understand while managing a patient.

Key takeaways

Sugar can damage blood vessels in the brain, which can trigger cognitive decline. Furthermore, high insulin levels secondary to type 2 diabetes can imbalance other brain chemicals, contributing to dementia. Moreover, high blood sugar causes inflammation, damaging brain cells and triggering dementia.

Although the full relationship between diabetes and dementia needs to be further studied, enlightening research does exist. It’s also important to understand diabetes and dementia as potential comorbidities when managing patients.

Examining risk

Results from a longitudinal study published in JAMA indicated that in patients aged between 35 and 75 years, for every onset of diabetes 5 years earlier, there was a higher hazard of dementia. Late-onset diabetes, however, was not related to dementia onset.

In other findings, there was no significant association between prediabetes and dementia, although stroke and diabetes comorbidity led to additional dementia risk.

1. The Alzheimer’s Association cited the following research findings related to the increased risk of dementia in people with diabetes.
2. There’s a strong association between high blood sugar levels and increased beta-amyloid protein, which is a marker for Alzheimer's disease.
3. Individuals with type 2 diabetes exhibit signs of accelerated cognitive decline such as impairments in executive function and information-processing speeds.
4. Difficulties with memory, related to the hippocampus region of the brain, already occur in patients who’ve had diabetes for less than 10 years. The hippocampus is smaller in patients with diabetes than in those without.
5. Even in early diabetes, higher levels of insulin resistance can occur in the brain, along with a decreased ability to utilize glucose as brain fuel.
6. The amyloid precursor gene, operative in Alzheimer's disease, could potentially disrupt insulin pathways. This could shed light on potential new drug targets.

Possible mechanisms

1. The JAMA study researchers proposed possible mechanisms tying diabetes and dementia. For instance, decreased transport of insulin via the blood-brain barrier could lead to deficiencies in insulin signalling and lowered cerebral glucose use, thereby contributing to brain metabolic dysfunction that mediates dementia.
2. Another hypothesis links peripheral and cerebral insulin resistance. Higher levels of systemic resistance lead to glucose neurotoxicity, vascular injury, and accumulation of advanced glycation end products, which could contribute to dementia.

The last hypothesis implicates the effects of periods of hypoglycemia, which can occur with the use of insulin. Cumulative effects of hypoglycemia in insulin-dependent type 2 diabetes could contribute to dementia over the long term.

Managing comorbid diabetes and dementia

Given the coexistence of diabetes and dementia, the Alzheimer’s Association encourages patients to act upon Life’s Simple 7 modifiable risk factors as a strategy to both manage their diabetes and reduce their risk of cognitive decline:

• Blood pressure control
• Cholesterol control
• Decreasing blood sugar
• Becoming physically active
• Eating better
• Dropping excess weight
• Smoking cessation

This list was originally developed by the American Heart Association, which advises that individuals start by targeting one or two risk factors and ramping up from there. Continuous glucose monitoring may be a good idea to gauge eating patterns in elderly patients with both diagnoses.

This story is contributed by Naveed Saleh and is a part of our Global Content Initiative, where we feature selected stories from our Global network which we believe would be most useful and informative to our doctor members.