Brain health matters. We’ve learned much about the interactions between physical health and the health of the brain. Now, a new study found links between prediabetes, common among Western nations, and declining brain health. We might want to pay attention.
The study in question comes from the University College London Institute of Cardiovascular Science and the UCL MRC Unit for Lifelong Health & Aging. It was published in the journal Diabetes, Obesity and Metabolism.
For the study, researchers analyzed data from the UK Biobank of 500,000 people. Their average age was 58 years. Researchers found that people with higher than normal blood sugar levels were 42% more likely to experience cognitive decline over an average of four years. They were also 54% more likely to develop vascular dementia over an average of eight years (although absolute rates of both cognitive decline and dementia were low.)
Even after accounting for other influencing factors like age, smoking, deprivation, and the presence of cardiovascular disease, the results remained the same.
A person is said to have prediabetes if their blood sugar levels are higher than usual, but not high enough to warrant a diagnosis of Type 2 diabetes. It’s an indicator of being at risk of developing diabetes. It’s believed that 1 in 3 Americans has this condition.
Lead author Dr Victoria Garfield said: “Our research shows a possible link between higher blood sugar levels — a state often described as ‘prediabetes’ — and higher risks of cognitive decline and vascular dementia. As an observational study, it cannot prove higher blood sugar levels cause worsening brain health. However, we believe there is a potential connection that needs to be investigated further.
“Previous research has found a link between poorer cognitive outcomes and diabetes but our study is the first to investigate how having blood sugar levels that are relatively high — but do not yet constitute diabetes — may affect our brain health.”
The research team looked at how different glycemic states (blood sugar levels) were connected to performance on cognitive test over time, along with dementia diagnoses. They also used MRI scans of the brain to measure brain structure. Smaller subsets of the Biobank sample were used for each of these tests. For example, follow-up cognitive tests were performed on only 18,809 participants.
At the time of their recruitment, each participant was given an HbA1c test. This measures blood sugar levels over the previous two to three months. The results allowed the researchers to split the participants into five different groups. These were “low-normal” blood sugar, normoglycemia (normal blood sugar levels,) prediabetes, undiagnosed diabetes and diabetes. The prediabetes group was identified as those with blood sugar levels between 42 – 48 mmol/mol (6.0 – 6.5%.)
Using data from repeated assessments of visual memory, researchers determined if participants were suffering cognitive decline. Absolute rates of cognitive decline were low overall. However, those with diabetes and prediabetes exhibited higher likelihood of cognitive decline – 42% and 39% respectively.
Based on a review of dementia diagnoses, prediabetics appeared to have a higher likelihood of vascular dementia. This common form of dementia is caused by reduced blood flow to the brain. The diabetic group was three times more likely to develop vascular dementia than those with normal blood sugar. They were also at higher risk for Alzheimer’s disease.
Senior author Professor Nishi Chaturvedi (UCL MRC Unit for Lifelong Health & Ageing) said: “In this relatively young age group, the risks of cognitive decline and of dementia are very low; the excess risks we observe in relation to elevated blood sugar only modestly increase the absolute rates of ill health. Seeing whether these effects persist as people get older, and where absolute rates of disease get higher, will be important.
“Our findings also need to be replicated using other datasets. If they are confirmed, they open up questions about the potential benefits of screening for diabetes in the general population and whether we should be intervening earlier.”
35,418 participants received a MRI brain scan. Among these, prediabetes was moderately associated with a smaller hippocampus. It was also strongly linked with having brain lesions, or white matter hyperintensitied (WMHs.) These are associated with age-related cognitive impairment.
High blood pressure may contribute to some of the differences, according to the researchers. Those participants taking antihypertensive drugs were more likely to have smaller hippocampus volume and to have more WMHs. Researchers believed this was the result of earlier, untreated high blood pressure, rather than a side effect of the medications.
The good news is that prediabetics can reduce their risk of developing Type 2 diabetes, and even reverse their condition, by eating a healthy, balanced diet, maintaining a healthy weight and becoming more active. In other words, lifestyle choices matter when it comes to your weight, your blood sugar and, by extension, your brain health!
Keep the faith and keep after it!
Journal Reference – Victoria Garfield, Aliki‐Eleni Farmaki, Sophie V. Eastwood, Rohini Mathur, Christopher T. Rentsch, Krishnan Bhaskaran, Liam Smeeth, Nish Chaturvedi. Brain health across the entire glycaemic spectrum: the UK Biobank. Diabetes, Obesity and Metabolism, 2021; DOI: 10.1111/dom.14321