A new research finds that lower weight in seniors is associated with an increased risk of dementia, and weight loss correlated with a more rapid decline in Alzheimer’s disease. Brigham and Women’s Hospital and Massachusetts General Hospital conducted a study that observed older people who were considered cognitively normal and had a lower body mass index (BMI) had more widespread deposits of beta-amyloid protein in the brain. This is a protein that is the primary component of plaques characteristic of Alzheimer’s disease.
The degradation of nerve cells in the brain, which causes the symptoms associated with Alzheimer’s disease, is thought to be through the formation of amyloid plaques and neurofibrillary tangles. The first stage of the preclinical form of Alzheimer’s disease is believed to be elevated cortical amyloid. This suggests that individuals who are underweight late in life may be at greater risk for this disease, according to senior author Dr. Gad Marshall, of the MGH and BWH Department of Neurology. Therefore, being underweight as you get older may not be a good thing when it comes to your brain health.
There are 3 stages to the hypothesized preclinical form of Alzheimer’s. The individual is cognitively normal but has raised amyloid deposits in the first stage. In the second stage they see an added level of evidence of neurodegeneration. Otherwise, elevated tau deposits or brain tissue loss typical of Alzheimer’s disease. The final and third stage adds cognitive changes within normal range but is a decline for the individual.
The findings of this study has been published in the Journal of Alzheimer’s Disease and part of the MGH-based Harvard Aging Brain Study (HABS), aiming to identify markers that predict those people most likely to develop Alzheimer’s and how soon their symptoms are likely to be noticeable. This study included 280 older adults from 62 to 90 years old, cognitively normal and in good health who were among the first to enroll in HABS.
Data was provided by the participants such as medical histories, physical exams, testing for APOE4 gene, a gene associated with a higher risk of late-onset Alzheimer’s disease, and PET imaging with Pittsburgh compound B (PiB), which can visualize amyloid plaques in the brain. After adjusting for age, sex education and APOE4 status, results showed lower BMI was associated with greater retention of PiB, which indicated a higher amount of amyloid brain deposits.
The weight and extensive amyloid deposits association was more prominent in normal-weight participants who had the lowest BMI of the groups. The lower BMI and greater PiB retention were most significant in those individuals with the APOE4 gene variant.
An explanation for the association is that low BMI is an indicator for frailty, a syndrome involving reduced weight, slower movement and loss of strength that is known to be associated with Alzheimer’s risk. There is also a study to show whether BMI is associated with any other clinical and imaging markers of Alzheimer’s disease.
-Dr Fredda Branyon