Obesity accelerates onset of Alzheimer’s disease, study finds

Obesity may hasten the development of Alzheimer’s disease, according to new research that sheds light on how excess weight affects the brain.

Dementia currently affects an estimated 982,000 people in the UK and obesity is already recognised as a significant risk factor. The Alzheimer’s Society notes that being obese between the ages of 35 and 65 can raise the likelihood of developing dementia later in life by around one-third. This may be due to obesity’s links with high blood pressure and type 2 diabetes, both of which are known contributors to dementia risk.

Now, scientists in the United States have, for the first time, demonstrated a direct connection between obesity and the progression of Alzheimer’s disease using blood tests.

A new study reports that blood biomarkers associated with Alzheimer’s increased up to ninety-five per cent faster in individuals with obesity compared with those of a healthy weight. The findings will be presented at the annual meeting of the Radiological Society of North America (RSNA).

Researchers analysed five years of data from 407 participants, including brain scans and blood samples. Lead author Soheil Mohammadi, a postdoctoral research associate at the Mallinckrodt Institute of Radiology, said the lower levels of blood biomarkers (BBMs) observed in obese participants were likely due to dilution caused by greater blood volume.

Dr Mohammadi noted that, at first glance, these lower biomarker levels might suggest a reduced risk of Alzheimer’s in people living with obesity. However, long-term tracking revealed the opposite: participants living with obesity showed significantly faster accumulation of amyloid plaques, the protein deposits that characterise Alzheimer’s.

Those living with obesity experienced a twenty-nine per cent to ninety-five per cent faster increase in plasma pTau217 ratio levels — a strong indicator of the presence and progression of Alzheimer’s disease.

Senior author Dr Cyrus Raji said the study demonstrated that blood tests were more sensitive than brain scans in detecting the impact of obesity on Alzheimer’s development. He suggested that combining blood biomarker tracking with brain imaging is likely to become standard practice for monitoring treatment effectiveness and the use of anti-amyloid drugs.

The study focused on a blood test that measures p-tau217, a protein strongly linked to amyloid plaque formation. Although initial cross-sectional data showed higher body mass index (BMI) correlated with lower BBMs and reduced amyloid plaques, the longitudinal findings revealed that obesity was associated with markedly faster Alzheimer’s-related changes over time.