Demographic changes require an adapted approach to managing type 1 diabetes (T1D) and age-related conditions such as dementia. While associations between T1D, structural brain changes and cognitive decline have been documented, their interplay has been insufficiently understood. “Prior studies on dementia subtypes have been inconsistent, so there was a need to replicate both the link between T1D and all-cause dementia, as well as its subtypes,” says Naveed Sattar (University of Glasgow, UK), co-author of a recently published study led by Thomas van Sloten (University Medical Center Utrecht, Netherlands).

The results of their nationwide, register-based analysis were published in Diabetes Care. Overall, the study showed that people with T1D were about two times more likely to develop all-cause dementia, with a median age of detection that was almost 5 years younger. All examined subtypes of dementia (Alzheimer’s disease, vascular dementia, and non-Alzheimer–nonvascular dementia) were elevated in the T1D group, with vascular dementia showing the highest hazard ratio.

Van Sloten says: “I believe our study provides the clearest evidence to date that T1D increases the risk of all-cause dementia and its major subtypes, and it identifies potentially modifiable risk factors that could help mitigate this risk.”

All-cause dementia two times more likely

The study used data from the Swedish National Diabetes Register (n = 43,440) and matched it to the Swedish Total Population Register (n = 217,109) by age, sex, and county. The investigators examined the incidence of all-cause dementia as the primary outcome, and the incidence of dementia subtypes as the secondary outcome. They also evaluated risk factors specifically within the T1D population.

Over a median follow-up period of 14.3 years, dementia developed in 530 (1.2 %) of participants living with T1D versus 1,867 (0.9 %) of controls, yielding a hazard ratio (HR) of 2.02 (see Figure 1). The median age at first dementia diagnosis was 71.1 years for people with T1D, compared with 75.9 years for controls. The risk of all-cause dementia was similar for men and women.

Vascular dementia emerges as the dominant subtype

The excess risk for vascular dementia stood out clearly in the analysis: the HR reached 3.7, far exceeding the increase observed for Alzheimer’s disease with an HR of 1.38, van Sloten notes.

“This strong finding suggests that cerebrovascular injury – ranging from large-vessel stroke to microvascular dysfunction or small-vessel disease – is a major pathway linking T1D to dementia.”

A central driver of this vascular vulnerability is chronic hyperglycaemia, the authors suggest based on their findings.

As Sattar explains: “The short- and long-term effects of elevated glucose on both large and small vessels, including those supplying the kidneys, heart, and importantly the brain, are well established. People with T1D experience decades of higher glucose levels, a major risk factor for accelerated kidney and heart damage, and similar injury may occur in the cerebral blood vessels and neural tissue. Kidney damage can further accelerate the risks of heart disease and stroke, which in turn can speed up cognitive decline.”

Risk factors highlight vascular pathways

In addition, the authors assessed risk factors for dementia within the T1D group. Older age, being single, higher systolic blood pressure and HbA1c levels, and a history of cardiovascular events, stroke or transient ischaemic attack (TIA) were all significantly linked to an increase of all-cause dementia risk. Longer diabetes duration, in turn, showed a link to vascular dementia.

“The association of vascular risk factors is consistent with chronic hyperglycaemia causing microvascular damage, neurovascular dysfunction, and metabolic stress, all of which contribute to cognitive decline,” notes van Sloten.

Interestingly, achieving guideline targets for HbA1c, blood pressure, body mass index, and albuminuria at baseline was not associated with a reduced risk of dementia in the study. 

 “Although meeting the recommended clinical targets for risk factors at baseline was not statistically significantly associated with a lower dementia risk, reducing or meeting those risk factor targets over time may be more informative regarding dementia risk,” Sattar explains, emphasizing that this point remains uncertain and requires further investigation. “As outlined in our paper, our findings suggest that preventing cardiovascular disease in individuals with T1D may help protect against dementia,” he adds.

What’s in it for the clinic?

Clinicians should be aware of the increased risk of dementia, particularly vascular dementia, in people with T1D. Yet systematic screening remains challenging, van Sloten and Sattar both emphasise.

“Currently, we cannot predict who among people with T1D is at the highest risk of late-life dementia, and there are no ‘diabetes-specific’ red flags,” says van Sloten. Sattar adds: “Many people with T1D are simply too young to be affected, so there is no clear consensus on screening for cognitive risk factors. General risk signals for dementia include early symptoms such as memory loss, difficulty concentrating, and struggling with familiar tasks.”

Looking ahead, more research is needed to develop T1D-specific guidance. In the meantime, Sattar recalls the importance of well-established measures:

“We can all work to lower dementia risks in people with T1D by keeping glucose levels as good as possible – modern pumps and devices for continuous glucose monitoring help with this whilst limiting side effects – as well as keeping cholesterol, blood pressure and smoking down or at target levels. These are the keys. The rest of the advice applies to everyone: try to keep your weight down, stay active, and keep your mind engaged – although this is not always easy.”

Key Points:

• People with type 1 diabetes (T1D) face more than double the risk of all-cause dementia, with the greatest increase seen in vascular dementia.

• Vascular risk factors, including stroke/transient ischaemic attack (TIA) and elevated blood pressure, appear central to dementia risk in T1D. The authors suggest long-term hyperglycaemia as the major driver behind the vascular pathogenesis.

• Despite the rising incidence of dementia in ageing populations with T1D, there are no T1D-specific early markers and more research is needed to improve predictive tools.

To read this paper visit: Jancev M, Eliasson B, Gerstein HC, et al. Dementia Risk in People With Type 1 Diabetes and Associated Risk Factors: A Nationwide, Register-Based Cohort Study. Diabetes Care. 2025;48(11):1888-1895. doi:10.2337/dc25-0773

Author: Hanna Gabriel, BA MSc. Any opinions expressed in this article are the responsibility of EASD e-Learning.