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Studies have linked type 2 diabetes to dementia at a later age, but the link between the two conditions, causal or otherwise, still needs to be clarified.
A review by researchers from the Department of Geriatric Medicine, Peninsula Health, Central Clinical School, published in the highly impressive International Journal of Clinical Endocrinology & Metabolism, highlighted the need to further explore potential mechanisms and pathways linking the two conditions.
The article “New Horizons-Cognitive Dysfunction Associated with Type 2 Diabetes” also emphasizes the importance of physicians who identify and manage treatment in people with coexisting type 2 diabetes and cognitive dysfunction.
Professor Velandai Srikanth, director of the National Center for Healthy Aging, was invited by the magazine to conduct a review. It is a topic that his group has been researching intensively. “Connection is not something that is usually talked about, but people have become more aware of it in the last 10 or 15 years,” said Professor Srikanth.
“Several studies about 15 years ago showed that type 2 diabetes was associated with a twofold increase in dementia in later years – but what could be the cause? Is diabetes the cause of an increasing risk of dementia, or is there another set of mechanisms?
The answers are important. Type 2 diabetes is widespread and affects approximately 463 million people worldwide. One in five adults over the age of 65 has diabetes, mostly type 2, according to the review.
Increasing age is also associated with an increased incidence and prevalence of cognitive dysfunction and dementia. In 2015, an estimated 46.8 million people with dementia lived worldwide, and this number is expected to double every 20 years.
Clinicians will increasingly be tasked with managing older people with type 2 diabetes and cognitive dysfunction. There is also great research interest in whether type 2 diabetes is a direct causal factor in the pathogenesis of cognitive decline and dementia, the review states.
A narrative review, written from a clinical evaluation basis in 164 articles, discusses the potential mechanisms and pathways linking these two comorbidities and factors such as high blood glucose, blood pressure, and lifestyle changes.
“My theory is that the effect of diabetes, the way diabetes is related to the brain, goes through several pathways, and each of these pathways may play a small role in the overall effect,” said Professor Srikanth. “If you just try to deal with one path or one treatment for a single path, such as blood pressure tablets or cholesterol tablets, then you may not be dealing with the whole package, so the treatment may not be successful.”
Advances in brain dysfunction measurement technology will help in understanding potential mechanistic pathways and lead recommendations for clinical practice, the review said.
“There may be better ways to capture the effects of diabetes on the brain in the future with much more sensitive brain measurements using MRI or PET scans.”
Professor Srikanth said he hoped the article would help inform physicians about the problems associated with treating people with comorbidities.
Challenges for researchers and physicians in the future include the development of: testable frameworks for the early identification of people with type 2 diabetes at risk for future cognitive problems; feasible and sustainable clinical response models for caring for such people to prevent future cognitive decline; and a strong evidence base for the ideal treatment of diabetes and its complications in patients with predominant cognitive dysfunction or dementia.
The first author is geriatrician / research assistant associate professor Chris Moran.
To read a previous review on a topic first written by Professor Srikanth, see Lancet Diabetes and Endocrinology.