Type 2 diabetes and Alzheimer’s disease: what health professionals need to know
People living with diabetes may raise concerns about a possible link between diabetes and Alzheimer’s disease. As a health professional, having a clear and balanced understanding of the evidence can support informed, reassuring conversations.
By Carolien Koreneff, Credentialled Diabetes Educator
What is Alzheimer’s disease?
Alzheimer’s disease is the most common form of dementia. It is a progressive neurodegenerative condition characterised by changes in memory, thinking, language, and functional ability. Although age is the strongest risk factor, Alzheimer’s disease is not a normal part of ageing.
The link between type 2 diabetes and Alzheimer’s disease
Evidence consistently shows that type 2 diabetes is associated with an increased risk of Alzheimer’s disease. A key mechanism thought to underpin this association is insulin resistance.
Insulin plays an important role in the brain, supporting glucose uptake and neuronal function. In the context of insulin resistance:
- Brain cells may have reduced access to glucose
- Energy supply to neurons may be compromised
- Cognitive processes such as memory and executive function may be affected over time
There is also emerging evidence of insulin signalling dysfunction within the brain itself, which may contribute to neurodegenerative changes.
“Type 3 diabetes”: clarifying the term
The term “type 3 diabetes” is sometimes used in research to describe insulin resistance occurring in the brain. However:
- It is not a recognised clinical diagnosis
- It is not used in routine clinical care
- Its use can be confusing for patients
Health professionals should avoid using this terminology in patient education, and instead focus on clear, evidence-based explanations.
Risk: association, not inevitability
While type 2 diabetes is associated with a ~50–65% increased risk of Alzheimer’s disease, it is important to communicate that:
- Many people with diabetes do not develop dementia
- Alzheimer’s disease also occurs in people without diabetes
- Risk is multifactorial
Key contributing factors include:
- Age
- Genetics
- Cardiovascular health
- Physical activity
- Cognitive and social engagement
Diabetes should therefore be framed as one modifiable risk factor within a broader risk profile.
Why glucose management matters for brain health
The brain has high energy demands, relying heavily on glucose to support cognition. Both acute and chronic glycaemic factors can influence brain function:
Short term:
- Hypoglycaemia and hyperglycaemia may impair concentration, attention, and decision-making
Long term:
- Chronic hyperglycaemia contributes to vascular damage, including cerebral circulation
- This may increase risk of cognitive decline and vascular contributions to dementia
Supporting individuals to achieve personalised glucose targets remains central to both diabetes and brain health.
Supporting brain health in people with diabetes
Many strategies recommended for diabetes management also support cognitive health. Key areas to reinforce in practice include:
1. Physical activity
- Improves insulin sensitivity (systemic and possibly central)
- Enhances cerebral blood flow
- Supports neuroplasticity
2. Glucose management
- Encourage consistent monitoring and individualised targets
- Reduce risk of both acute cognitive effects and long-term vascular complications
3. Cardiovascular risk management
- Blood pressure control
- Lipid management
- Smoking cessation
These factors are strongly linked to both diabetes complications and dementia risk.
4. Cognitive and social engagement
- Encourage mentally stimulating activities, learning, and social connection
- Supports cognitive reserve and resilience
Communication tips for clinical practice
When discussing this topic with clients:
- Emphasise that risk is increased, not predetermined
- Avoid alarmist or deterministic language
- Reinforce that modifiable factors make a meaningful difference
- Encourage early discussion of cognitive concerns
Key messages for practice
- Type 2 diabetes is associated with an increased risk of Alzheimer’s disease, but is not a direct cause
- Insulin resistance, including in the brain, is a proposed mechanism
- “Type 3 diabetes” is a research term and should not be used clinically
- Optimising diabetes and cardiovascular care supports both physical and cognitive health
- Preventive strategies overlap significantly with standard diabetes management