Higher BMI in middle age linked to changes in brain thickness in later life
By Alex Smith | Thursday 25 July 2019
Neurology: Measures of obesity are associated with MRI markers of brain aging
Researchers from the University of Miami Miller School of Medicine have found a link between a high body mass index and brain features that are associated with a higher risk of developing Alzheimer’s disease.
The study, published in the journal Neurology on the 24 July, involved 1,289 men and women of different racial backgrounds with an average age of 64. The majority (66%) of the participants were from Hispanic and Latino backgrounds, and 60% of the people included in the study were women. Scientists measured people’s waist and hips as well as using their height and weight to calculate their Body Mass Index (BMI). After an average of six years the study participants had an MRI brain scan. Scientists used images from the MRI scan to measure the volume and the thickness of different regions of the brain.
The researchers were interested in the thickness of the outermost layer of the brain, often referred to as the grey matter. Having a thinner layer of grey matter has been linked to an increased risk of Alzheimer’s disease.
The scientists found that people who had a BMI of over 25, meaning they are considered overweight had a thinner layer of grey matter. The effect was more pronounced in obese people who had a BMI of over 30. The scientists reported that the link was strong even in those who were younger than 65 years old. As well as the association with BMI, a larger waist measurement was also linked to a thinner layer of grey matter.
Dr James Connell, Research Manager at Alzheimer’s Research UK, said:
“We know that the diseases that cause dementia cause changes to the brain years before symptoms start to show, so our health in midlife can have an impact on our brain later on. Living a healthy lifestyle, including maintaining a healthy weight, can reduce our risk of developing dementia. While BMI can help determine whether a person may be overweight, this measure is not a good indication of general health on its own. This study only shows a correlation between BMI and MRI measures of brain aging and does not suggest that being overweight causes dementia.
“Previous studies have shown a link between being overweight and increased dementia risk, and the amount of grey matter in the brain. While this study links a higher BMI and waist measurement to a thinner layer of grey matter in the brain, it does not report whether the participants were diagnosed with Alzheimer’s disease. Further studies are needed to investigate the exact relationship between weight and differences in grey matter both in normal aging and in people with Alzheimer’s disease.
“This study was conducted over a fairly short period of time, so couldn’t draw conclusions about the difference between people from different backgrounds, although the researchers suggest that future studies should look at the impact of obesity on the brains of different groups of people. A longer and larger study would be needed to unravel these differences.”