Diabetes and dementia

The connection

Type 2 Diabetes is associated with around double the risk of dementia, through vascular damage, insulin resistance in the brain, and effects on amyloid clearance. Pre-diabetes (HbA1c 42 to 47 mmol/mol) also raises risk. The Lancet Commission identifies diabetes as one of the 14 modifiable dementia risk factors.

Targets

NICE NG28 recommends:

• HbA1c target: usually 48 mmol/mol on lifestyle alone, or 53 mmol/mol on one glucose-lowering medication;
• Individualised in older adults to balance glycaemic control against hypoglycaemia risk;
• Tight control particularly in early disease;
• Avoidance of hypoglycaemia (low blood sugar) which is itself harmful.

Lifestyle

• Weight: even 5 to 10 per cent weight loss substantially improves glycaemic control;
• Diet: Mediterranean Diet, lower carbohydrate, attention to refined carbohydrates and sugary drinks;
• Exercise: 150 minutes of moderate activity a week, plus resistance work;
• Sleep: untreated Sleep Apnoea worsens glucose control;
• Alcohol: within UK limits.

Medication

Metformin

First-line for most people. Lowers blood glucose by reducing liver glucose production. Side effects include diarrhoea (usually transient) and Vitamin B12 deficiency on long-term use (check annually). Some observational evidence suggests possible cognitive benefit beyond glucose lowering.

SGLT2 inhibitors

Empagliflozin, Dapagliflozin, Canagliflozin. Lower glucose by increasing urinary excretion. Strong evidence for cardiovascular and kidney protection beyond glucose lowering. May reduce dementia risk although direct trial evidence in dementia is still emerging.

GLP-1 receptor agonists

Semaglutide (Ozempic, oral or injectable Rybelsus, weight-loss formulation Wegovy), Liraglutide. Improve glucose control and produce substantial weight loss. Active research interest in Alzheimer's Disease (trials underway with Semaglutide).

Other classes

Sulfonylureas (Gliclazide), DPP-4 inhibitors (Sitagliptin), Pioglitazone, insulin. Each has a specific role; older adults benefit from approaches with low hypoglycaemia risk.

Avoiding hypoglycaemia

Hypoglycaemia (low blood sugar) is independently associated with dementia risk in older adults. Choose medications and regimens with low hypoglycaemia risk:

• Metformin, SGLT2 inhibitors, GLP-1 receptor agonists, DPP-4 inhibitors (low risk);
• Sulfonylureas (Gliclazide, Glimepiride) carry hypoglycaemia risk; use cautiously in older adults;
• Insulin has the highest hypoglycaemia risk; tight insulin regimens not always appropriate in older adults.

For people with established dementia

Glycaemic targets relax in established dementia, particularly in moderate to severe disease, to avoid hypoglycaemia. HbA1c targets of 58 to 64 mmol/mol may be more appropriate in this group. Medication regimens are simplified; insulin is used cautiously.

Pre-diabetes

HbA1c 42 to 47 mmol/mol indicates pre-diabetes (impaired glucose regulation). Lifestyle measures alone can prevent progression in many people. The NHS Diabetes Prevention Programme offers structured support across the UK.