Minireview: mechanisms by which the metabolic syndrome and diabetes impair memory

Type 2 diabetes is associated with an increased risk of cognitive dysfunction. These effects seem particularly true for memory functions. This article examines how diabetes and the biological changes that occur with diabetes such as hyperglycemia, changes in insulin concentration, hypertension, and changes in lipid levels might lead to these alterations in cognitive functioning, with an emphasis on the mechanisms leading to changes in memory. OTH type 1 (insulin-dependent diabetes mellitus, or IDDM) and type 2 (non-insulin-dependent diabetes mellitus, or NIDDM) diabetes have detrimental effects on cognitive functioning (measures of verbal and numerical reasoning, attention, concentration, verbal and visual memory, and verbal fluency) and may increase the risk of dementia. In type 1 diabetes, chronic hyperglycemia and the recurrence of hypoglycemia appear to be associated with loss of cognitive ability (1‐3). A recent review of cognition in type 2 diabetes concluded that despite the poor design and lack of statistical power in many studies, type 2 diabetes appears to be associated with an increased risk of cognitive dysfunction in a wide array of cognitive tests (4). These findings are borne out in larger epidemiological studies (5,6). In particular, in those studies that examined it, loss of verbal memory was most consistently associated with diabetes. This article examines how diabetes and its risk factors might lead to these changes in cognitive functioning, with a particular focus on memory. M EMORY