The link between type 1 diabetes and the brain matters most in childhood, when the central nervous system is still growing and organising itself and depends on glucose as its main source of energy. Type 1 diabetes is an autoimmune disease: the immune system destroys the cells in the pancreas that make insulin, so people with the condition need treatment for life. It usually starts in childhood or young adulthood, and the article on diabetes in young adults explains how to spot the first signs.
A study published in 2026 in The Journal of Clinical Endocrinology and Metabolism found some differences in the brains of children more exposed to high blood sugar (hyperglycaemia). The authors are paediatric diabetologists, neuroradiologists and psychologists from Vita-Salute San Raffaele University, IRCCS San Raffaele Hospital (IRCCS is the official title for research hospitals in Italy) and other centres, including the IRCCS Carlo Besta Neurological Institute and Politecnico di Milano. Professor Riccardo Bonfanti, a paediatric diabetologist, and Professor Anna Lucia Ogliari, a clinical psychologist, help explain what these results mean.
The study compared 16 children with type 1 diabetes and 8 children of the same age without diabetes. The children were about two years old when the disease began and were assessed at around ten, after years of regular metabolic check-ups.
The researchers used three types of MRI scan to look at the structure of the brain, the fibres that connect its different areas and the brain’s activity at rest. They then compared these data with glycated haemoglobin (HbA1c), the value that shows average blood sugar over the previous months, and with a working memory test.
Half of the children with diabetes had been treated from diagnosis with multiple daily insulin injections, the standard treatment until a few years ago. The other half had used an insulin pump from the start, a device worn on the body that releases insulin continuously.
In the first group, the scans showed lower grey matter and white matter integrity. Grey matter is the tissue that holds the cell bodies of neurons, while white matter is made up of the fibres that connect them. Communication between different areas of the brain was also altered, compared with both the children using a pump and their peers without diabetes. With the pump, exposure to high blood sugar was about 30% lower.
The study also points to a specific area, the right inferior frontal gyrus, a region of the frontal lobe that helps with attention and impulse control. Its volume varies with average blood sugar over the past few years, and these differences partly explain why the children with higher blood sugar scored lower on the memory test.
What many families fear most is hypoglycaemia, or low blood sugar: it can come on suddenly and cause a loss of consciousness. However, the sensors that measure blood sugar give an early warning when levels are falling, and mild hypoglycaemia is easy to correct with fast-acting sugars. «The real problem for the central nervous system, on the other hand, is hyperglycaemia», says Riccardo Bonfanti, Associate Professor of Paediatrics at UniSR and head of the Paediatric Diabetology and Metabolic Disorders Unit at IRCCS San Raffaele Hospital.
«The sample we analysed is small, and the results describe an association that needs to be confirmed in larger studies. Today, a comparison like this would also be hard to repeat, because almost all children with diabetes receive technologically advanced treatment from the start and more consistently have metabolic values close to normal. But having such effective technology available is one more reason to cut the time spent with high blood sugar as much as possible», he stresses.
Executive functions are the skills that let us plan, switch from one task to another, keep information in mind and hold back an impulse. «They’re what helps us stay on track during the day, and they mature throughout childhood and adolescence», notes Anna Lucia Ogliari, Associate Professor of Clinical Psychology at UniSR.
In type 1 diabetes, according to Ogliari, executive functions play a dual role: «they’re a very important tool for patients’ well-being and health, but they can also be a target of the disease». Bonfanti points out that in the study of 16 children, metabolic control was linked to executive functions, which Ogliari’s team assessed. He describes the mechanism as a vicious circle: «worse control leads to worse executive functions, which in turn lead to worse control: it becomes harder for the patient to follow the doctors’ instructions, and their health gets worse».
Researchers have studied the link between diabetes and executive function mainly in teenagers. In 2014, a review published in Current Diabetes Reports brought together the available research. According to the authors, executive functions are linked to how well patients stick to their treatment and to blood sugar control, although larger studies that follow patients over time are needed. A 2025 study in Pediatric Diabetes involved 88 teenagers aged 13 to 17 and their parents. Teenagers who had more difficulty with executive functions said they kept up with their daily care less consistently and felt more stress about their condition.
Managing type 1 diabetes means making many small decisions every day, and almost all of them rely on executive functions. Planning comes first. The bolus, the insulin dose that covers a meal, is given before eating, at the time set by the diabetologist: usually 15 to 20 minutes before. People who use insulin pens give themselves an injection, while those with a pump enter the meal’s carbohydrate count into the device and start the bolus.
At a restaurant, if the food arrives late, blood sugar can drop quickly and the person has to act. Working memory is needed too, to keep track of the carbohydrates in each portion and work out the dose. Then there is impulse control, for example when friends offer an unplanned slice of pizza. Before and during the teenage years all this is harder, because the prefrontal cortex, which regulates impulse control, only finishes maturing in early adulthood.
Then there is organisation: sensors and pump sets have to be changed at fixed intervals, and supplies need checking often. Even a happy, exciting event such as a trip brings its own worries and needs careful thought. «Families, or young patients, have to think about how to pack their suitcase. How many spare sets should they take? How many sensors? Where should they keep the insulin? There are lots of questions», says Ogliari.
Until a few decades ago, blood sugar was measured by pricking a finger several times a day, even in children. To find out whether blood sugar had stayed stable over several months, families had to wait for the check-up and the HbA1c result. Today a continuous glucose monitoring (CGM) sensor, applied to the skin, measures blood sugar all the time, while the pump adjusts insulin directly. In the most advanced systems, known as hybrid artificial pancreas or hybrid closed-loop systems, the two devices work together. «They’re insulin pumps that talk to a sensor via Bluetooth, and inside the pump there’s a computer that can manage 50% of insulin delivery automatically», Bonfanti explains.
«This system lets us improve blood sugar levels while limiting these patients’ exposure to hypoglycaemia, which is a source of fear and worry for families», he adds. One limitation remains. Before every meal, the patient (or the parent, for younger children) still has to tell the pump how many carbohydrates they are about to eat and start the bolus. Researchers are working on a fully automatic system, known as a fully closed-loop system, but it will take time before these devices are in common use.
The sensor measures blood sugar every few minutes and stores all the readings. On a phone or computer, the data become graphs and reports. The most widely used measure in diabetes care is time in range: the percentage of time that blood sugar stays between 70 and 180 milligrams per decilitre (3.9–10 mmol/L). In 2019, an international group of experts, backed by the main diabetes societies, published general targets in Diabetes Care. They recommended more than 70% of the time in this range and less than 4% below 70 mg/dL (3.9 mmol/L), and stated that diabetologists should tailor the targets to each person. Parents can receive the readings on their phone even when they are away from their child, and so can the diabetes team.
At camps for young people with diabetes, Ogliari says, downloading the data becomes a game: «we look at the graphs and data together, but not to criticise». Reading the graphs together helps young people understand what changes their blood sugar, such as sport, periods or a stressful day. It also helps them recognise their body’s signals, which they often learn to read well enough to spot a change before the sensor alarm goes off.
Work on the link between type 1 diabetes and the brain continues. The aim is to understand how executive functions and blood sugar control affect each other. Another question is whether a tendency to be more introverted or more impulsive makes that circle more virtuous or more vicious. In the long term, the team would like to develop easy-to-use tools for children, such as tablet and smartphone apps, designed to train executive functions. The article on type 1 diabetes in children describes how children grow up with the condition and how families can be supported.
Training executive functions makes sense because the brain changes seen in these studies seem to be at least partly reversible. Bonfanti cites a US study of 42 teenagers with type 1 diabetes, published in 2022 in Nature Communications. After six months, those using a hybrid artificial pancreas had more stable blood sugar and brain development closer to what is typical in adolescence. Their scores on some reasoning tests were higher than those of teenagers on standard treatment. The authors describe the results as preliminary and in need of confirmation through longer studies, but conclude that good blood sugar control can prevent or partly reverse these effects.
At UniSR, Bonfanti also coordinates the Master in Paediatric Endocrinology and Diabetology, a second-level postgraduate course that trains doctors in these areas.