Low blood sugar impairs brain function ‘A hypo disrupts more than just the daily rhythm’

People with diabetes who use insulin regularly have a hypo. This low blood sugar level impairs information processing by the brain, according to PhD research by Clementine Verhulst of the Radboud university medical center. By activating the immune system, hypos may also cause damage to the heart and blood vessels.

A hypo. People with diabetes know all too well what this means. Due to a low blood sugar level, they experience all kinds of symptoms. These range from sweating, nervousness, and disturbed vision to confusion, muscle spasms, and even epileptic seizures. PhD research by Clementine Verhulst of the Radboud university medical center reveals that the brain is less able to process information during a hypo. She also shows that hypos have a long-term impact on the immune system.

Surprisingly discomforting

In her research, Verhulst induced hypos through controlled administration of insulin and sugar, taking over the sugar regulation of the body. She did this in people with diabetes as well as in healthy subjects. This was quite something for the latter group. ‘These people experienced a hypo for the first time’, says Verhulst. ‘They were really surprised how discomforting it is.’

She then investigated whether a hypo affects the processing of information by the brain. This revealed that people score much worse during a hypo, regardless of whether they have diabetes or not. The type of diabetes also makes no difference. Verhulst: ‘That is striking. Because type 1 diabetes often manifests itself at a young age, people have lived with their disease for so long that they become accustomed to hypos. They are less aware of hypos and think that they function just fine. That turns out not to be the case.'

Verhulst also shows that a hypo activates the immune system. For example, the abundance of a certain type of immune cell in the blood increased. And not only during the hypo, but also a week later. This cell type aggravates the immune response by producing much more inflammatory proteins compared to other immune cells. Finally, the research shows that the effects on the immune system also occur upon repeated exposure to hypos. So there was no habituation effect apparent here either.

Cardiovascular diseases

Internist Bastiaan de Galan, who led the studies, explains what these findings mean for people with diabetes: 'They should be aware that they function much worse during a hypo, even though they may be used to it. Consider, for example, driving a car. There are also plenty of people who say that they can still drive perfectly after three beers, because they are used to it. But that is also not the case.’

The influence of hypos on the immune system may contribute to the development of cardiovascular diseases. These are very common in people with diabetes, but the underlying cause has not yet been fully elucidated. De Galan: 'Inflammation is known to damage the heart and blood vessels, so hypos may indeed play a role. Our research makes it clear that a hypo is much more than just an annoying disruption of the daily rhythm.’

More information about this PhD thesis defense

PhD thesis defense of Clementine Verhulst on June 20th at 10.30 p.m. Title of dissertation: Effects of hypoglycaemia on cognition and inflammation (available online after June 20th). (Co-)supervisors: prof. dr. B.E. de Galan, prof. Dr. C.J.J. Tack, and dr. ir. R. Stienstra. The defense can be followed via this livestream.
 

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