Poor Glucose Control Linked To Brain Volume Shrinkage In The Elderly

Older adults suffering from either pre-diabetes or full blown diabetes show significantly greater rates of brain volume shrinkage according to the results of a study presented this month at the joint conference of the International Congress of Endocrinology and European Congress of Endocrinology.

The research, led by Dr. Katherine Samaras, Associate Professor of Medicine at the University of New South Wales in Australia, focussed on 312 adults aged between 70 and 90 who were followed up over 2 years. MRI scans were taken of the participants at the beginning and end of the study to determine total brain volume.

The participants were divided into 4 groups: normal glucose levels at both the beginning and end of the study, impaired fasting glucose (prediabetes) at beginning and end of study, worsening glucose levels during the study (progression from normal glucose to IFG or diabetes, or progression from IFG to diabetes), and full blown diabetes at beginning of the study.

While every group experienced brain shrinkage over the course of the study, decreases in brain volume occurred at a slower rate in the group that maintained normal glucose levels throughout the study. Brain shrinkage in this group was measured at 18.4cm3, compared to 26.6cm3 in the stable pre-diabetic group, 41.7cm3 in the group that experienced a decline in glucose control, and 42.3cm3 in the diabetic group.

A decrease in brain volume is a normal feature of old age and not necessarily an indicator of dementia however substantial reductions in brain size can result in memory loss, mood swings, an inability to pick up new information, and a general decline in cognitive ability.

The researchers believe that the results are likely due to either a direct toxic effect of high blood sugar on the brain similar to the damage high blood sugar does to the peripheral nervous system, or from other factors that are associated with diabetes such as chronic inflammation and high body fat levels.

Furthermore, insulin promotes the development of atherosclerosis, which can impair the flow of blood to the brain, leading to multiple micro-strokes in the brain and the development of vascular dementia. Insulin resistance is a common finding in diabetics and is characterized by chronic high insulin levels.

Previous studies have linked diabetes with a substantially higher risk of developing dementia, particularly vascular dementia. A Dutch study, conducted in 1999 found that individuals with diabetes had 1.9 times greater risk of developing dementia compared to non-diabetics. The risk was greatest for diabetics who were receiving insulin to treat their condition, this group had a 4.3 fold increased incidence of dementia.