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Lower weight in older people may increase their risk of Alzheimer’s

A new study carried out by researchers from Brigham and Women’s Hospital and Massachusetts General Hospital has suggested that there may be a link between a lower body mass index (BMI) and an increased risk of Alzheimer’s in older people.

From their study, the team found that greater deposits of beta-amyloid plaques normally associated with Alzheimer’s disease were found in older people with a low BMI. This association was seen particularly in those people who had been identified as carrying the APOE4 gene variant, which is associated with an increase in the risk of developing the disease. As elevated amounts of cortical amyloid are believed to be first stage in the preclinical form of the disease, the research team have suggested that people who are underweight may be at a greater risk of developing Alzheimer’s.

This study was undertaken as part of the Harvard Aging Brain Study which is based in Massachusetts General Hospital. Through the identification of specific markers, the team aim to predict the people most likely to develop the disease, and to forecast the time frame for development of typical Alzheimer’s symptoms.

At present, the concept of a preclinical version of Alzheimer’s is still in the theory stage. However, scientists suggest that there are likely to be 3 phases. The first being where individuals are still classed as cognitively normal but have an increased amount of amyloid deposits. In the second phase the individual exhibits some evidence of degeneration of the neurons although cognition is not affected; while in the third preclinical stage, changes in cognition are seen although individuals still fall within the normal cognition range.

As part of their research the team explored the association between body mass index and the levels of beta amyloid in the brain. There were 280 participants in total, ranging in age from 62 to 90, all of whom were in good general health and classed as cognitively normal. As part of their enrolment, details of their medical histories were taken and participants underwent various physical exams and tests, including testing for the presence of APOE4. They also underwent PET imaging to check for amyloid plaques within the brain.

After the results had been adjusted for various factors, it was found that a lower body mass index was associated with a larger amount of amyloid plaques, and that this association was most significant in those people who also had the APOE4 gene.

While future research is needed to offer an explanation for these findings, the team believe that people with a lower BMI are generally more frail, a factor which is known to be associated with the risk of developing the Alzheimer’s.

The results of the study were reported in a recent edition of the Journal of Alzheimer’s Disease.


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