Is metformin the only culprit for cognitive impairment in diabetes?

Background
As diabetic patients conventionally are on a long-term prescription for metformin, it is important to identify any increase in their risk for developing cognitive disorders. Hence, an attempt was made here to study cognitive impairment by using the Montreal Cognitive Assessment test (MoCA) as a possible predictor of development of cognitive impairment in type 2 diabetics on metformin therapy.
Methods
400 Type 2 diabetics on metformin-containing anti-diabetic regimen were enrolled and data recorded. A cognitive test, MoCA, was administered and a score of less than 26 was considered abnormal. 
Results
In this study, the participants on metformin had a statistically significant correlation with age > 65 years, duration of diabetes (>5 years), metformin dose (1 gm and more) and presence of diabetes complications. Ordinal regressions showed significant correlation between abnormal MoCA scores and older age, longer duration of DM, and presence of one of the DM complications.
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