People with Alzheimer’s who also have abnormal protein clumps called Lewy bodies tend to have worse memory, thinking, and language skills at the start of their diagnosis, compared to those with only Alzheimer’s changes in the brain.

We analyzed the available evidence and found that people with Alzheimer’s who also have Lewy bodies—abnormal protein clumps in the brain—tend to show more severe memory, thinking, and language problems when first diagnosed, compared to those with Alzheimer’s alone [1]. This pattern was observed across all 54 studies or assertions we reviewed, with none contradicting it. Lewy bodies are made of a protein called alpha-synuclein, and while they’re most commonly linked to Parkinson’s disease, they can also appear in the brains of people with Alzheimer’s. When both are present, the brain faces two types of damage at once, which may make it harder to process information, recall memories, or find the right words. Our current analysis shows this combination is often tied to stronger symptoms early on, but we don’t yet know if Lewy bodies speed up decline over time or affect how someone responds to treatment. The evidence we’ve reviewed so far leans toward the idea that having Lewy bodies alongside Alzheimer’s changes is associated with a more challenging symptom profile from the start. However, we don’t have enough data to say whether Lewy bodies cause the worsening or if they simply appear together with other factors. For someone living with Alzheimer’s or caring for someone who is, this means that if memory or language problems seem unusually severe early on, it could be worth asking a doctor about the possibility of Lewy bodies being involved. It doesn’t change the overall approach to care, but it may help explain why symptoms feel more intense than expected.