Can type 2 diabetes lead to dementia? "Blood sugar control" and "changing risk factors" are key!

Studies have shown that the average life expectancy of people with diabetes is 5-10 years less than that of people without diabetes, but their life expectancy can be increased with improved treatment, which means that people with type 2 diabetes will also have a higher risk of developing other chronic diseases that are closely related to aging or metabolic abnormalities, such as cognitive decline and dementia.

However, limited evidence exists regarding glycemic control and dementia risk in people with type 2 diabetes. Furthermore, do potential risk factors differ by dementia subtype?

Recently, a study from the University of Gothenburg and the Swedish National Diabetes Registry explored this in detail, and the results were published in Diabetes Care, a journal of the American Diabetes Association (ADA). The results found that the relationship between type 2 diabetes and dementia varies by subtype, and the strongest association between vascular dementia and the risk of type 2 diabetes is found. In addition, patients with type 2 diabetes who have poor blood sugar control are at particularly increased risk of vascular and non-vascular dementia.

Screenshot source: Diabetes Care

The research team used data from the Swedish National Diabetes Register, including approximately 380,000 people with type 2 diabetes and nearly 1.89 million age- and sex-matched controls.

The primary outcome of the study was the incidence of Alzheimer's disease, vascular dementia, and nonvascular dementia (analyzed using Cox regression models). The association between type 2 diabetes and dementia was stratified by baseline glycated hemoglobin (HbA1c) in patients with type 2 diabetes only.

The average age of the two groups was 64 years old, and 55% of them were men. The results found that there were the following associations between type 2 diabetes and dementia:

During follow-up (median 6.8 years), 11,508 (3.0%) people with type 2 diabetes developed dementia (2320 with Alzheimer's disease, 2155 with vascular dementia, and 7033 with nonvascular dementia) and 52,244 (2.7%) people in the control group developed dementia (12,834 with Alzheimer's disease, 7629 with vascular dementia, and 31,781 with nonvascular dementia).

Compared with the control group, after adjusting for sex, income, education, country of birth, and the presence or absence of cardiovascular disease, patients with type 2 diabetes had a 34% increased risk of vascular dementia (HR 1.34 [95%CI 1.28, 1.41]) and a 10% increased risk of non-vascular dementia (HR 1.10 [95%CI 1.07,1.13]). The risk of Alzheimer's disease in patients with type 2 diabetes was 6% lower than that in the control group (HR 0.94 [95%CI 0.90, 0.99]).

The researchers also found a linear association between HbA1c concentration and dementia risk, with the magnitude of the association varying by dementia subtype.

The strongest association was found for vascular dementia.