Type 2 Diabetes Mellitus and Dementia


Type 2 Diabetes Mellitus (Diabetes) has been linked to vascular dementia and Alzheimer’s disease. The causal relationship is unclear but it may result from the biologic effects associated with Diabetes. For example, inflammation may damage blood vessels in the brain leading to brain cell injury. Inflammation may also raise cortisol concentrations which can increase blood pressure.


Long-term studies of the risk of dementia in elderly people with diabetes have consistently shown an overall increase in the incidence of dementia by 50% relative to people without the disease.[1] It’s possible that Individuals with Diabetes also are more likely to have cardiovascular diseases such as stroke, TIA, or heart attack that could cause brain injury and contribute to dementia.


It’s estimated that eliminating diabetes and increasing fruit and vegetable consumption may lead to an overall 10% reduction in the incidence of dementia.[2] The Mediterranean diet has been associated with lower risk of developing Alzheimer’s disease. This diet is high in vegetables legumes, fruits, unsaturated fatty acids, and low intake of dairy products, meat, and saturated fatty acids with moderate alcohol use. Adherence to the Mediterranean diet is associated with borderline reduction for developing mild cognitive impairment (MCI). It is also associated with a reduced likelihood that MCI will progress to Alzheimer’s disease.[3]


It’s not clear how the Mediterranean diet improves cognition but the same diet lowers vascular risk factors such as high cholesterol, hypertension, and coronary heart disease. It likely works by preventing vascular insults to the brain like inflammation and stroke.[4] In addition, the Mediterranean diet may improve carbohydrate processing. It leads to significant reductions in plasma glucose and serum insulin, leading to less insulin resistance.[5] Insulin resistance or Type 2 diabetes can be measured by a blood test such as hemoglobin A1C (HbA1C) or fasting plasma glucose. HbA1C is a good indicator of how well blood sugar has been controlled over the previous 30 days. In general, HbA1C below 5.7% is considered normal; 5.7% to 6.9% with fasting plasma glucose of 100mg/dL to 126 mg/dL is pre-diabetic; and 7% or greater with fasting plasma glucose greater than 126mg/dL is diabetes. Medical treatment for diabetes is recommended for those with consistent HbA1C scores of 7% and higher.[6]

Refer to Healthy Diets for more information.


[1] Velayudhan, L, Poppe M, Archer N, et.al., Risk of developing dementia in people with diabetes and mild cognitive impairment. BJP 2010;196:36-40.

[2] Ritchie K, Carriere I, Ritchie CW, et.al., Designing prevention programmes to reduce incidence of dementia: Prospective cohort study of modifiable risk factors. BMJ 2010;341:c3885

[3] Scarmeas N, Stern Y, Mayeus R, et.al., Mediterranean diet and mild cognitive impairment, Arch Neurol. 2009;66(2):216-225.

[4] Singh RB, Dubnov G, Niaz MA et.al. Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): A randomized single-blind trial. Lancet 2002;360(9344):1455-1461.

[5] Esposito K, Margella R, Ciotola M, et al. Effect of a Mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome: A randomized trial. JAMA, 2004;292(12):1440-1446.

[6] 2017 VA/DoD clinical practice guidelines for the management of type 2 diabetes mellitus in primary care.