People with poor metabolic health are more likely to have problems with memory and thinking, as well as poorer brain health, according to a new study by researchers at Oxford Population Health. The study, published in the journal Diabetes Care, is the largest study to date on metabolism and brain health.
Poor metabolism, also known as “metabolic syndrome,” is defined as three or more of the following: large waist circumference, high triglycerides, high blood pressure, high blood sugar, and low high-density lipoprotein (HDL) cholesterol (also known as “good” cholesterol). Worldwide, metabolic syndrome affects one in four adults.
Previous studies have shown that poor metabolism may increase the risk of developing dementia, but it was unclear whether poor metabolism also leads to poor brain health in people without dementia. Preserving both brain structure and cognitive ability is crucial for healthy aging, and loss of both can negatively impact brain health and signal the progression of dementia.
The researchers investigated whether poor metabolic health affects brain volume and cognitive performance by analysing the results of 37,395 UK Biobank participants who did not have dementia, 7,945 of whom had poor metabolic health at the time they entered the UK Biobank study.
Key findings:
Poor metabolic health can lead to:
A decrease in total brain volume and in the volume of gray matter, which is responsible for processing information in the brain; An increase in white matter hyperintensities, an indicator of vascular brain damage that has previously been associated with dementia; Memory impairment, indicated by a decrease in hippocampal volume and poorer performance on cognitive tests of working memory (a type of short-term memory) and verbal declarative memory (the ability to recall and repeat information); Poorer performance on cognitive tests of processing speed (how quickly information is processed), verbal and numerical reasoning (the ability to understand and manipulate words and numbers), nonverbal reasoning (the ability to understand information that is not represented in words or numbers, such as pictures and diagrams), and executive function (involved in planning and problem solving).
Daniel Qureshi, a PhD student at Oxford Population Health and lead author of the study, said: “Our findings indicate that poor metabolic health is associated with reduced brain volume and impaired cognitive performance, which may contribute to the development of dementia later in life. It is estimated that up to 40% of dementia could be prevented by changing diet and lifestyle. Maintaining metabolic health may therefore be crucial to reducing the risk of dementia and related brain disorders.”
Dr Thomas Littlejohns, senior epidemiologist at Oxford Population Health and lead author of the study, said: “Poor metabolic health is thought to play an important role in the future risk of developing dementia. Interestingly, our findings show that poor metabolic health is associated with poor brain health even in people without dementia. These findings were consistent across different age groups, including people in their 50s, 60s and 70s. The next step will be to see whether better prevention, treatment and management of metabolic conditions can lead to improved brain health in both middle age and old age.”
Madeleine Wolpert, researcher at Dementia UK, said: “This large-scale study highlights the importance of being aware of conditions that can increase the risk of dementia and present with dementia-like symptoms. Our findings show that metabolic syndrome reduces grey matter volume and increases vascular damage in the brain, affecting cognitive performance across domains such as memory and processing speed, mimicking some of the hallmark symptoms of dementia.”
“This evidence supports the need to understand how multiple conditions interact and manifest together, particularly as nine in 10 people with dementia also have another long-term health condition. It is important to treat and care for people holistically, addressing not only each individual condition but also the interactions between co-existing conditions and the impact they have collectively on their overall health and wellbeing.”
The researchers used data from the UK Biobank, a collection of more than 500,000 men and women aged 40 to 69 who took part in studies between 2006 and 2010. Since 2014, more than 50,000 participants have undergone additional assessments, including undergoing brain imaging and a range of cognitive tests. Combining these data with other information has allowed scientists to provide unprecedented insight into how age-related diseases develop.
Detailed findings Total brain volume: β = -0.06 (95% CI: -0.08, -0.04) Gray matter volume: β = -0.10 (95% CI: -0.12, -0.08) Left hippocampal volume: β = -0.03 (95% CI: -0.05, -0.01) Right hippocampal volume: β = -0.04 (95% CI: -0.07, -0.02) White matter hyperintensity volume: β = 0.08 (95% CI: 0.06, 0.11) Working memory: β = -0.10 (95% CI: -0.13, -0.07) Verbal declarative memory: β = -0.08 (95% CI: -0.11, -0.05) Processing speed: β = -0.06 (95% Verbal and Numerical Reasoning: β = -0.07 (95% CI: -0.09, -0.04) Non-Verbal Reasoning: β = -0.03 (95% CI: -0.05, -0.01) Executive Function*: β = 0.03 (95% CI: 0.01, 0.06); β = 0.05 (95% CI: 0.03, 0.08)
*Higher scores indicate poorer cognitive ability
This study used standardized beta coefficients to assess the strength and direction of the relationship between metabolic syndrome (MetS) and various indices of brain health. Indices were standardized to allow for comparison of effect sizes across outcomes. For example, a beta value of -0.06 for total brain volume indicates that having MetS is associated with a 0.06 standard deviation reduction in total brain volume compared to not having MetS.
Beta coefficients measure how much the dependent variable changes with a one-unit change in a predictor variable, holding all other predictors constant. They measure the strength of the relationship between each predictor variable and the dependent variable, and the direction of that relationship (positive or negative).
