The research on blood sugar levels and cognitive decline
For the study, published in the journal Diabetes, Obesity and Metabolism, the researchers analyzed data from the UK Biobank including 500,000 people aged 58 on average, and found that people with higher than normal blood sugar levels were 42% more likely to experience cognitive decline for an average of 4 years, and they were 54% more likely to develop vascular dementia for an average of 8 years (although the absolute rates of cognitive decline and dementia were low).
The associations remained true after factoring other influencing factors, including age, sleep deprivation, smoking, BMI, and whether or not the participants suffered from cardiovascular disease. People with prediabetes had higher than usual blood sugar levels, but not high enough to be diagnosed with type 2 diabetes. It means they were at higher risk of developing diabetes. There are roughly five to seven million people with prediabetes in the UK.
Lead author Dr. Victoria Garfield (UCL Institute of Cardiovascular Science and UCL MRC Unit for Lifelong Health & Aging) said: “Our research shows a possible association between higher blood sugar levels, a condition that is often referred to as “prediabetes”, and increased risk of cognitive impairment and vascular dementia. Being an observational study, higher blood sugar levels couldn’t be shown to impair brain health. Nonetheless, we believe there is a potential connection that needs to be researched further.
“Previous research has found an association between poor cognitive outcomes and diabetes, but our study is the first to examine how having high blood sugar levels, although not yet diabetes, can affect our brain health.” In the study, the researchers looked at how different blood sugar levels, or glycemic states, were associated with performance on cognitive tests over time, dementia diagnoses, and brain structure measured by MRI brain scans. Each of these tests was limited to smaller subsets of the Biobank sample (for example, only 18,809 participants had follow-up cognitive tests).
At the time of recruitment, all UK Biobank participants underwent an HbA1c test, which determined their average blood sugar levels over the past two to three months. The participants were divided into five groups based on the results: “low-normal” blood sugar, normoglycemia (having a normal blood sugar level), prediabetes, undiagnosed diabetes, and diabetes. A result between 42-48 mmol/mol (6.0 – 6.5%) was deemed as prediabetes.
The researchers used data from repeated visual memory assessments to determine whether or not the participants were experiencing cognitive decline. Although the absolute rates of cognitive decline were low, people with prediabetes and diabetes had a similarly higher chance of cognitive decline: 42% and 39% respectively.
The findings
When looking at dementia diagnoses, the researchers found that prediabetes was associated with an increased likelihood of vascular dementia, a common form of dementia caused by reduced blood flow to the brain, but not Alzheimer’s disease. Moreover, people with diabetes were 3 times more likely to develop vascular dementia than people whose blood sugar levels were deemed as normal, and they were more likely to develop Alzheimer’s disease.
Lead author, Professor Nishi Chaturvedi (UCL MRC Unit for Health and Lifelong Aging) said: “In this relatively young age group, the risks of cognitive decline and dementia are very low; the excessive risks observed, associated with high blood sugar levels are minor.” It will be important to see whether these effects persist as people age and when absolute rates of disease increase.
“Our findings need to be replicated using other data sets as well. If confirmed, they open up questions about the possible benefits of diabetes detection among the general population and about whether we should intervene earlier”. Among the 35,418 UK Biobank study participants who underwent MRI brain scans, the researchers found that prediabetes was somehow associated with a smaller hippocampus and it was more strongly associated with brain lesions (white matter hyperintensities, WMH), both associated with age-related cognitive impairment.
The researchers affirmed that some of these differences could be explained by a high blood pressure, since participants taking antihypertensive medications are likely to have more WMH and smaller hippocampal volume. Rather than the treatment having an adverse effect on the brain, the researchers said that the use of such a drug could be an indicator of previous untreated high blood pressure. People with prediabetes can reduce their risk of developing type 2 diabetes by eating a healthy and balanced diet, by being more active, and by maintaining a healthy weight.
Link: https://www.sochob.cl/web1/12959-2/
Date: February 13th, 2021
Source: https://medicalxpress.com
Reference: Garfield V, Farmaki AE, Eastwood SV, et al. Brain health across the entire glycaemic spectrum: the UK Biobank. Diabetes Obes Metab. 2021 Jan 19. doi: 10.1111/dom.14321.
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