People who have both Alzheimer’s and another brain condition called Lewy bodies show more severe energy loss in certain back parts of the brain than people with just Alzheimer’s, which means the two conditions together might mess up brain function in unique ways.

We analyzed the available evidence and found that people with both Alzheimer’s and Lewy bodies tend to show more severe energy loss in certain back regions of the brain compared to those with Alzheimer’s alone [1]. This energy loss, called brain hypometabolism, means those brain areas are using less glucose — their main fuel — which can affect how well they work. The evidence we’ve reviewed so far leans toward this pattern being more pronounced when the two conditions occur together. We did not find any studies that contradicted this observation. While we can’t say why this happens or what it means for symptoms or progression, the pattern suggests that having both conditions may affect the brain differently than Alzheimer’s by itself. This could help explain why some people with both diseases experience unique problems, like visual hallucinations or movement issues, that are less common in Alzheimer’s alone. Our current analysis is based on one assertion supported by 54.0 studies or data points, with no refuting evidence. More research is needed to understand how this energy loss connects to daily symptoms or how it might change over time. For now, the pattern points to a possible difference in brain function when Alzheimer’s and Lewy bodies occur together.