Associations between the Use of Metformin and Behavioral and Psychological Symptoms in Patients with Alzheimer´s Disease, and Type 2 Diabetes Mellitus - A Register-based Study.

Background: Metformin, the first-line anti-diabetic drug treatment in patients with type 2 diabetes mellitus (T2DM), is suggested to be anti-inflammatory, antioxidative, and improve cognitive function, making it a promising contribution to treating Alzheimer´s disease (AD). However, the effect of metformin on behavioral and psychological symptoms of dementia (BPSD) in patients with AD has not been explored.

Objective: To investigate the associations between metformin and BPSD in patients with AD and T2DM and explore possible interaction with other antidiabetic drugs.

Methods: This cross-sectional study was based on data from the Swedish BPSD register. A total of 3745 patients with AD and antidiabetic drug treatment were included. Associations and interactions between antidiabetic drugs and BPSD were investigated by binary logistic regression.

Results: The use of metformin was associated with lower odds for symptoms of depression (OR 0.77, CI (95%) 0.61-0.96, p = 0.022) and anxiety (OR 0.74, CI (95%) 0.58-0.94, p = 0.015) after adjustment for age, gender, specific diagnosis, and drugs. We could not demonstrate this association with another antidiabetic drug. Interaction effects were limited to an increasing association in eating and appetite disorders using metformin and other antidiabetic drugs (i.e., drugs other than insulin, sulfonylurea, or dipeptidyl peptidase-4 inhibitors).

Conclusion: The result of this study suggests that metformin could be beneficial for patients diagnosed with AD, other than for blood glucose control. Although, more knowledge is needed before assigning metformin a role in treating BPSD.