Type 2 diabetes and its impact on the brain


Diabetes has detrimental consequences on brain function and mental state in the elderly, since it accelerates cognitive decline and increases the risk of the onset of depressive symptoms and cerebrovascular accidents (CVA) of ischemic origin in the elderly.

In the general population, diabetes prevalence is around 5% and 10% in subjects over 65, with an increasing proportion as the population ages (25% in those over 75 ).

However, with the improvement of our lifestyle and the existence of effective preventive measures against stroke, diabetics are able to live longer with fewer major complications.

Diabetes decreases the faculties of the brain

There is growing evidence that diabetes impairs brain function.

Diabetes increases the risk (by about 100%) of seeing decline in cognitive functions, compared to non-diabetics.

The association between diabetes and arterial hypertension – which is associated with a more pronounced decline in cognitive abilities – being very frequent, it is difficult to assess the exact role of diabetes.

In 2014, researchers found that people who develop diabetes or hypertension between the ages of 40 and 64 are more likely to have neuronal loss and/or cognitive disorders (memory problems, thought disorders)

According to one of the study authors (Mayo Clinic), « if we prevent diabetes and hypertension, we can prevent or delay brain damage that occurs decades later ».

To reach this conclusion, the researchers recruited 1,437 people with an average age of 80 who underwent neuroimaging examinations to detect markers associated with brain damage.

Results: people with diabetes have an average brain volume 3% smaller than that of non-diabetic subjects. Such a reduction in volume is also observed in patients who suffer from hypertension.

The researchers conclude that these diseases take decades to produce their deleterious effects on the brain, leading to cognitive impairments that affect memory and thinking.

In the same year, another group showed that type two diabetes could be associated with premature brain aging, according to a study carried out on 614 patients (average age = 62 years) followed for an average of 10 years.

This conclusion is in line with previous studies that reported a link between type 2 diabetes and ischemia affecting small vessels, a disease during which the brain does not receive enough oxygenated blood.

« These patients show less brain tissue, suggesting the presence of cerebral atrophy, » said one of the study’s authors.

The authors used the magnetic resonance imaging technique to assess the patients’ brain volume. The results further reported a positive association between duration of diabetes and loss of brain volume, particularly in gray matter. More specifically, the results suggest that a person with diabetes for 10 years exhibits premature brain aging (of a period of 2 years) compared to a non-diabetic patient.

These results are in line with those of previous longitudinal studies, confirming that the cognitive functions of diabetics deteriorate more rapidly.

In a six-year follow-up study of a group of 9679 women over the age of 65, diabetics whose disease had been evolving for more than 15 years had a 57 to 114% increased risk of presenting with cognitive decline.

Several hypotheses have been put forward to explain this link:

  • Hyperglycemia affects neurons in the hippocampus, a key brain region involved in learning and remembering events.
  • Diabetes is accompanied by inflammation in the brain – called neuroinflammation  – which also damages neurons.
  • Dysregulation of glucose levels affects neurons in the brain that produce a neurotransmitter called acetylcholine. This neurotransmitter is necessary to obtain a memory.
  • The microalbuminuria (low amounts of albumin in the urine) present in diabetics reflects a dysfunction of the vascular system which prevents poor oxygenation of the brain.

Research is investigating the possible beneficial effects of treating diabetes with insulin in preventing cognitive decline. This is particularly the case of intranasal insulin injections which would provide protection to the brain.

Watch out for hypoglycaemia

The brain is particularly sensitive to changes in blood sugar – especially hypoglycemia. The consequences of hypoglycaemia can be serious in elderly diabetics. Thus, elderly people with diabetes are five times more likely to be hospitalized than younger people due to a greater risk of hypoglycaemia.

A study suggests that hypoglycemia, which occurs frequently in patients with diabetes, can negatively influence cognitive performance. These cognitive disorders will in turn compromise the management of diabetes and lead to hypoglycemia.

These are the conclusions of an American study (University of California, San Francisco) involving 783 adults (average age 74 years) with diabetes. After 12 years of follow-up, 8% had a reported episode of hypoglycaemia and 19% developed dementia.

Patients who had a hypoglycemic event had a twice as high risk of developing dementia compared to those who did not (34% versus 17%).

In addition, elderly diabetics who have developed dementia have a greater risk of subsequently having an episode of hypoglycemia compared to patients who have not developed dementia (14% versus 6%).

Obtaining a normal blood sugar level would improve – or at least maintain – his cognitive performance.


Diabetes: a risk factor for vascular dementia ?

Diabetes is a risk factor for cerebrovascular accident (CVA) which promotes the development of vascular dementia, with a risk multiplied by 2 to 2.6 according to studies. If the individual has suffered a stroke, this risk can be multiplied by eight. The presence of hypertension in diabetics plays an important role in this increase.

Alzheimer’s disease

Diabetes could also be a cardiovascular risk factor in the onset of Alzheimer’s dementia, with an estimated increased risk of between 45% and 90% depending on the studies.

However, this link is questioned by other studies.

Better prevention of dementia would be possible thanks to a normalization of blood sugar, in the same way as arterial hypertension.

The Depression

Depression can be mistaken for dementia or, conversely, can be one of the first symptoms of Alzheimer’s disease. It is therefore important to detect it, which is often difficult.

According to scientific data, about 20 to 30% of elderly diabetics suffer from depression, including 10% from major depression. There would be at least one depressive symptom in half of elderly diabetics.

According to a study conducted in 2015 on people with diabetes (average age = 54 years), they have difficulties with family functioning and a lower quality of life.


Diabetes is usually considered one of the major risk factors for stroke, with an increased risk of 50% to 100%. The risk of stroke is all the higher when the subject is hypertensive, has atrial fibrillation, carotid stenosis or a history of stroke. In addition, the occurrence of a stroke in a diabetic is strongly associated with a high risk of disability and higher mortality.

In 2016, researchers showed that type 2 diabetics have a greater risk (+60%) of developing dementia, compared to those without diabetes. Additionally, women with type 2 diabetes have a much higher risk of developing vascular dementia than men with diabetes. Indeed, the risk of vascular dementia is multiplied by 2.3 in women and by 1.7 times in men, compared to those who do not have diabetes. The analysis included data from 14 studies with more than 2.3 million people and more than 100,000 cases of dementia.

These results suggest that diabetes increases the risk of developing vascular dementia and that women with diabetes are particularly vulnerable. A previous study reported that people with diabetes had a 70% increased risk of dementia. However, these results are limited by the fact that most cases of dementia were reported in people of Asian origin.

The researchers were unable to analyze the links between the duration of diabetes, glycemic control and dementia. They suggest, however, that treatment differences in diabetes management – ​​particularly poor care for women – may play a role in these results.

Further physiological studies are needed to examine how blood sugar interacts with the vasculature and whether there are notable gender differences.

On the other hand, diabetes seems to protect against the occurrence of hemorrhagic strokes, with a risk of stroke of hemorrhagic origin reduced by a factor of 4 to 10.


Stroke prevention is possible through risk factor control and better blood sugar control. Controlling blood pressure is an essential part of stroke prevention. However, too great a decrease in blood pressure can lead to a stroke through a drop in cerebral circulation.

The use of statins is also found to be very beneficial. Thus, simvastatin (40 mg) or atorvastatin (10 mg) can reduce strokes by 25% to 50%.

In addition, antiplatelet drugs are recommended to reduce the risk of stroke. Aspirin is very frequently used in elderly diabetics at high risk of stroke.

The surgical management of carotid stenosis does not differ from that of non-diabetic subjects. The occurrence of a stroke and the operative risk are higher, but the benefit of an intervention is greater in diabetics. The indication for surgery must therefore be established according to the general condition of the elderly subject and the severity of the stenosis.

 Diabetes increases the risk of heart and brain disease

The risk of developing cardiovascular disease is almost twice as high in patients who develop type 2 diabetes before age 40, compared to those who develop the disease later. The age of diagnosis of type 2 diabetes is getting younger around the world, mainly due to rising rates of obesity.

“Given the increasingly frequent onset of type 2 diabetes at an early age, it is hardly surprising that cardiovascular complications also appear earlier and earlier due to an increasingly unfavorable environment. a long time,” explains the lead author of the study.

The researchers used a large diabetes database, with participation from 630 hospitals and 222,773 patients. The average age of the cohort is 58.3 years. Patients who had early-onset diabetes were on average 34 years old, compared to 55 for those who developed diabetes later in life.

Early-onset type 2 diabetes was associated with a greater risk (+91%) of diseases associated with the brain and heart system (coronary heart disease and stroke), compared to late-onset diabetes.

According to some experts, the best way to measure risk in young patients with type 2 diabetes is to identify and treat cardiovascular risk factors. A very high proportion – around 80% – of young people with type 2 diabetes have at least two cardiovascular risk factors.

Septuagenarians are healthier than their elders

Americans with diabetes born in the 1940s live longer without major complications and with fewer disabilities than those born 10 years earlier.

These major complications are heart attack, stroke and amputations.

The three types of disability were reduced mobility, inability to carry out activities of daily living and total or partial inability to carry out essential activities (use of the telephone, shopping, meal preparation, etc.).

The messages of the medical authorities aiming to sensitize the individuals to have a better hygiene of life are undoubtedly for something.

This health improvement also concerns people who are not necessarily diabetic. The data analysis focused on Americans born in the 1930s and 1940s, more than 10% of whom had diabetes.

However, this improvement may not last in the United States due to rising obesity rates and poorer lifestyles. In this country, the incidence of type 2 diabetes has more than doubled in the last 20 years

Diabetes and brain disease article references

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Bardenheier BH et al. Compression of disability between two birth cohorts of US adults with diabetes, 1992–2012: a prospective longitudinal analysis. The Lancet Diabetes and Endorinology, June, 2016.  

Bryan RN et al. Effect of diabetes on brain structure: the action to control cardiovascular risk in diabetes MR imaging baseline data. Radiology. July 2014: 210-6.    

Chatterjee S et al. Type 2 Diabetes as a Risk Factor for Dementia in Women Compared With Men: A Pooled Analysis of 2.3 Million People Comprising More Than 100,000 Cases of Dementia. Diabetes care, December 2015.

Huo X et al. Risk of non-fatal cardiovascular diseases in early-onset versus late-onset type 2 diabetes in China: a cross-sectional study. The Lancet Diabetes & Endocrinology, Volume 4, No. 2, p115–124, February 2016.

Roberts RO et al. Association of type 2 diabetes with brain atrophy and cognitive impairment. Neurology, 2014. 

Saedi E et al. Diabetes mellitus and cognitive impairments. World J Diabetes 2016 September 15; 7(17): 412-422.

Wang J et al. Depressive Symptoms, Family Functioning and Quality of Life in Chinese Patients with Type 2 Diabetes. Can J Diabetes 39 (2015).

Yaffe K et al. Association Between Hypoglycemia and Dementia in a Biracial Cohort of Older Adults With Diabetes Mellitus, Hypoglycemia and Dementia in Older Adults With DM. JAMA Internal Medicine, June 2013.