Why Do Diabetic Patients Develop Dementia Despite Managing Their Vascular Health? [Professor Ahn Cheol-woo's Encyclopedia of Hormones]

[Financial News]Hormones have been passed down and developed from species to species alongside the evolution of life. If there is a chemical substance that must exist as long as life exists, it is the hormone. In this sense, hormones are immortal. Through his column, Professor Ahn Cheol-woo aims to accurately explain hormones—the chemicals that govern the body—and offer ways to live a healthier and happier life. <Editor's note>


Diabetes has become a global epidemic, and another disease is increasing at an equally alarming rate: dementia. According to data from the World Health Organization (WHO), the number of people with dementia worldwide has reached 55 million and is increasing by 10 million each year. In 2021 statistics from OECD countries, South Korea's dementia incidence stood at 11 cases per 1,000 people, ranking 30th worldwide. By 2050, however, that figure is expected to jump to 41 cases, putting the country in fifth place globally. Even taking the aging population into account, this is an exceptionally rapid increase.
However, one surprising research finding has emerged. A joint study involving five European countries, including France, Italy and the United Kingdom, found that the probability of a person without diabetes developing dementia at age 70 was 8.9 per 1,000 people. Among those who had had diabetes for about five years, the probability rose to 10 per 1,000. It increased to 13 among those who had had the disease for six to 10 years, and to 18.3 among those who had had it for more than 10 years. In other words, if 1,000 people developed diabetes at age 50, 18 of them would develop dementia after turning 60.
The claim that diabetes is linked to cognitive function and accelerates the onset of dementia has been raised for many years. Diabetes is a disease in which high blood sugar makes the blood sticky, causing blood vessels to become blocked in various places. As the blood vessels narrow and blood pressure rises, it naturally becomes more difficult to deliver blood to the brain. Since the major complications of diabetes include cardiovascular disease and stroke, it is only natural that the disease affects brain function.
Another possible cause is the hypoglycemia that commonly occurs in people with diabetes. Because persistent high blood sugar is a problem for diabetic patients, they are expected to follow diets that consistently exclude carbohydrates and sugar. However, hypoglycemia can occur when such a diet is maintained too strictly or when the amount of insulin injected exceeds the amount of carbohydrates consumed. Hypoglycemia is fatal to the brain, which uses glucose as its sole energy source. It can damage the hippocampus and cause acute cognitive impairment, memory loss, dementia, dizziness and coma. Repeated episodes of hypoglycemia can completely eliminate the body's ability to regulate blood sugar, causing it to swing between high and low levels and greatly increasing the risk of death from acute coronary syndrome.
In addition, inflammation and oxidative stress caused by diabetes-related hyperglycemia and obesity may also contribute to the development of dementia.
However, these factors alone cannot fully explain the high incidence of dementia among people with diabetes. Dementia remains common even among diabetic patients who carefully manage their risk of stroke. Hypoglycemia also occurs mainly in patients with type 1 diabetes and in those with type 2 diabetes who use insulin, affecting about 25% of these groups. This makes it difficult to explain why dementia is more common among all diabetic patients. It is also puzzling that the incidence of Alzheimer's disease (AD)—dementia caused by the loss of brain nerve cells—is much higher than that of vascular dementia.
Could diabetes itself directly cause dementia? The link may lie in amyloid plaques and tau protein. In the early stages of Alzheimer's disease (AD), a small protein called amyloid is produced excessively in the brain. The tau protein then clumps together through hyperphosphorylation, eventually causing brain cells to die. Insulin plays a decisive role in the formation of amyloid plaques and the hyperphosphorylation of tau protein. It is possible that insulin acts directly on brain cells and causes AD.
/Ahn Cheol-woo, professor of endocrinology at Gangnam Severance Hospital

 


[email protected] Jung Myung-jin, medical specialist Reporter