Diabetes mellitus in the young and the old: Effects on cognitive functioning across the life span.

Mild to moderate cognitive decrements are a well-known phenomenon associated with diabetes mellitus. In this review, we provide an overview of the cognitive consequences of type 1 and type 2 diabetes based on hallmark studies that follow patients over an extended period of time. In patients with type 1 diabetes, cognitive dysfunction appears soon after diagnosis and can be found in individuals of any age. The magnitude of these effects is generally modest, although their severity is especially pronounced in those with early onset type 1 diabetes (diagnosis before 7 years of age) or those who have developed microvascular disease, such as proliferative retinopathy. Rates of type 2 diabetes have increased dramatically over the past 20 years, in part driven by the world-wide epidemic of obesity, and this form of diabetes is appearing at a progressively younger age. Again, cognition may be disrupted, particularly in those who are in poorer glycemic control, and there is some evidence to suggest that with increasing diabetes duration, the rate of cognitive decline is accelerated and the risk of dementia is increased significantly.