Diabetes-Associated Cognitive Impairment – Not Just For the Elderly




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The prevalence of type 2 diabetes is on the rise; it can actually be regarded as an epidemic propagating as a consequence of poor lifestyle choices – bad feeding habits and sedentarism. The International Diabetes Federation (IDF) estimates that there are over 380 million cases of diabetes throughout the world and predict that it may rise to around 600 million in the next 20 years.

One of the consequences of diabetes is cognitive decline. There are several studies showing that diabetes causes an acceleration of age-related cognitive decline. But it’s not just age-related cognitive decline – patients with diabetes also have a higher risk of developing cognitive decline associated with different brain pathologies. Diabetes increases the likelihood of developing vascular diseases, Alzheimer’s disease, mild cognitive impairment and dementia. Although these diseases have different onset mechanisms, they can all be potentiated by diabetes.

Hyperglycemia is known to increase neuronal cell death through oxidation processes and generation of free radicals, thereby having neurodegenerative effects. Hyperglycemia can also cause damage to blood vessels through inflammatory mechanisms, leading to reduced blood flow to the brain and, consequently, reduced oxygen delivery, which results in the development of brain injuries.

If we add hypertension to the equation, which is commonly observed in patients with diabetes, vascular deficits become even worse, increasing the risk of stroke, for example, which is indeed more common in diabetic patients.

Younger diabetics are also at risk

This effect of diabetes is not only observed in the elderly. Although type 2 diabetes accelerates age-related cognitive decline, younger patients also show signs of cognitive impairment. In a study that followed dementia-free diabetic patients with a mean age of 40 years at the start of the study it was shown that, seven years later, diabetes had led to a degradation of memory, visual perception, and attention performance, as well as to a loss of brain integrity. Diabetes and higher fasting blood glucose levels were correlated with gray matter loss in the brain. This shows that cognitive decline is clearly anticipated in diabetes patients.

Another study, which followed patients with an average initial age of 54 throughout 10 years, showed that, compared with healthy participants, those with diabetes had a 45% faster decline in memory (10 year difference in decline), a 29% faster decline in reasoning, and a 24% faster decline in the global cognitive score. Furthermore, diabetes patients who had a poorer glycemic control had a faster decline in memory and reasoning, while participants with pre-diabetes or newly diagnosed diabetes had similar rates of decline to those with normal glycaemia.

It seems that the earlier the onset of diabetes, the higher the risk of accelerated cognitive decline. And even teenagers can be affected by the neurological consequences of type 2 diabetes. A pilot study following adolescents with type 2 diabetes showed that there are significant volume losses in a number of areas of the brain, as well as reduced white matter integrity. Given the fast increase in the incidence of type 2 diabetes (and other metabolic diseases) that is being observed in teenagers, this is clearly a reason for concern.

Therapeutic strategies designed to control glycaemia will most likely help reduce the effects of diabetes on the brain. Many of the mechanisms of diabetes-associated dementia and cognitive impairment can be counterbalanced by a good diet and by exercise. Early intervention is fundamental.

Just to show how important diet and exercise are to diabetes care: there is scientific evidence showing that lifestyle changes are actually more effective than antidiabetic drugs. But instead of using diet and exercise as a way to control all the detrimental effects of diabetes, it would actually be better to use them to prevent it.

References

Cheng, G., Huang, C., Deng, H., & Wang, H. (2012). Diabetes as a risk factor for dementia and mild cognitive impairment: a meta-analysis of longitudinal studies Internal Medicine Journal, 42 (5), 484-491 DOI: 10.1111/j.1445-5994.2012.02758.x

Chiu, W., Ho, W., Liao, D., Lin, M., Chiu, C., Su, Y., Chen, P., & , . (2015). Progress of Diabetic Severity and Risk of Dementia The Journal of Clinical Endocrinology & Metabolism, 100 (8), 2899-2908 DOI: 10.1210/jc.2015-1677

Rofey, D., Arslanian, S., El Nokali, N., Verstynen, T., Watt, J., Black, J., Sax, R., Krall, J., Proulx, C., Dillon, M., & Erickson, K. (2015). Brain volume and white matter in youth with type 2 diabetes compared to obese and normal weight, non-diabetic peers: A pilot study International Journal of Developmental Neuroscience, 46, 88-91 DOI: 10.1016/j.ijdevneu.2015.07.003

Sheen, Y., & Sheu, W. (2016). Association between hypoglycemia and dementia in patients with type 2 diabetes Diabetes Research and Clinical Practice, 116, 279-287 DOI: 10.1016/j.diabres.2016.04.004

Tuligenga, R., Dugravot, A., Tabák, A., Elbaz, A., Brunner, E., Kivimäki, M., & Singh-Manoux, A. (2014). Midlife type 2 diabetes and poor glycaemic control as risk factors for cognitive decline in early old age: a post-hoc analysis of the Whitehall II cohort study The Lancet Diabetes & Endocrinology, 2 (3), 228-235 DOI: 10.1016/S2213-8587(13)70192-X

van Praag, H., Fleshner, M., Schwartz, M., & Mattson, M. (2014). Exercise, Energy Intake, Glucose Homeostasis, and the Brain Journal of Neuroscience, 34 (46), 15139-15149 DOI: 10.1523/JNEUROSCI.2814-14.2014

Weinstein, G., Maillard, P., Himali, J., Beiser, A., Au, R., Wolf, P., Seshadri, S., & DeCarli, C. (2015). Glucose indices are associated with cognitive and structural brain measures in young adults Neurology, 84 (23), 2329-2337 DOI: 10.1212/WNL.0000000000001655

Image via TesaPhotography / Pixabay.

Sara Adaes, PhD

Sara Adaes, PhD, has been a researcher in neuroscience for over a decade. She studied biochemistry and did her first research studies in neuropharmacology. She has since been investigating the neurobiological mechanisms of pain at the Faculty of Medicine of the University of Porto, in Portugal. Follow her on Twitter @saradaes
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