Diabetes increased the risk for several associated diseases including heart disease, stroke, and kidney failure. Diabetes causes damage to the vascular system of the body and thus accelerates the atherosclerotic process primarily through increased inflammation. The chronic system inflammation that is caused by diabetes results in a pro-coagulant state which can lead to thrombus and micro-thrombus formation in the cerebral vasculature that result in clinical and subclinical stroke. This can lead to cognitive decline and accelerate the neuro-degeneration that is seen in the diseases of aging such as mild cognitive impairment and dementia. In fact, diabetes and high blood sugar levels are becoming increasingly seen as a risk factor for the development of dementia. We have previously discussed the toxic nature of excess sugar. We have also previously discussed the findings that diabetes is associated with increased risk of developing dementia and that newly diagnosed and poorly controlled diabetes accelerates cognitive decline. In addition, we have also discussed the finding that obesity decreases brain power and increases the risk of developing dementia in later life. Whether high normal blood sugars have a similar effect on cognition and brain function is unclear.
Researchers, led by Dr. Nicolas Cherbuin of the Australian National University in Canberra, Australia, have found that even high normal blood sugar levels are associated with atrophy of brain structures, the hippocampus and amygdala, involved in memory and cognitive function. The results of their study were published online in the journal Neurology. The researchers studied blood glucose levels and hippocampal and amygdalar atrophy in 266 cognitively healthy individuals aged 60 to 64 years without diabetes. Fasting plasma glucose levels and brain MRI imaging were recorded at the study start and four years later. The investigators found that blood glucose levels in the high normal range were strongly associated with hippocampal and amygdalar atrophy and accounted for 6 to 10% in the change in size after controlling for age, sex, body mass index, hypertension, alcohol, and smoking.
The authors wrote, “Given the robust prospective nature of this investigation and the detailed conservative controls undertaken, the present findings strongly suggest that higher glucose levels within what is considered the normal range are associated with greater hippocampal and amygdalar atrophy”.
A possible mechanism was given by the authors when they wrote, “Support for the involvement of inflammatory processes is available from a study which found that experimentally raised plasma glucose levels were associated with increased plasma cytokine levels (tumor necrosis factor, interleukin-6, and interleukin-10), both in healthy control subjects and in individuals with impaired glucose tolerance (IGT). However, inflammatory reactions peaked higher and lasted longer in subjects with IGT. These findings indicate that control of plasma glucose levels modulates systemic inflammatory responses and that individuals with [type 2 diabetes] are more likely to be exposed to longer lasting and stronger inflammatory states. Because chronic systemic inflammation has been shown to be associated with cerebral atrophy, particularly in the hippocampus, it is likely that consistently higher glucose levels within the normal range may be associated with neurodegeneration”.
The authors concluded, “These findings suggest that even in the subclinical range and in the absence of diabetes, monitoring and management of plasma glucose levels could have an impact on cerebral health. If replicated, this finding may contribute to a reevaluation of the concept of normal blood glucose levels and the definition of diabetes”.
This article adds to the growing body of evidence that high blood glucose levels caused by ingesting excess sugar or by diabetes/pre-diabetes is detrimental to health. In particular, even high normal blood sugar levels are detrimental to cognitive function and cause negative effects on important brain structures such as the hippocampus and amygdala. Future studies should focus on determining whether high normal blood glucose levels accelerated the progression of dementia and whether keeping blood glucose levels at a lower level prevents the changes observed in this study.
Nicolas Cherbuin et al. “Higher normal fasting plasma glucose is associated with hippocampal atrophy: The PATH Study” Neurology September 4, 2012 vol. 79 no. 10 pages 1019-1026 doi: 10.1212/WNL.0b013e31826846de