People with Alzheimer’s who also have Lewy bodies don’t have more of the Alzheimer’s proteins (amyloid and tau) than those without Lewy bodies. Their faster mental decline is probably because the Lewy body proteins add extra damage on top, not because their Alzheimer’s is worse.

We analyzed the available evidence and found that people with Alzheimer’s who also have Lewy bodies do not show more amyloid or tau buildup than those with Alzheimer’s alone. The presence of Lewy bodies doesn’t appear to make the core Alzheimer’s proteins increase in amount. Instead, the faster mental decline seen in these individuals may come from the added damage caused by Lewy body proteins themselves, not from a worsening of Alzheimer’s pathology [1]. What we’ve found so far suggests that Lewy bodies and Alzheimer’s proteins can coexist without one causing the other to grow more. Think of it like two different types of damage happening at once — one from amyloid and tau, another from Lewy body proteins — and together they may overwhelm the brain more quickly than either alone. This doesn’t mean Lewy bodies make Alzheimer’s worse in terms of protein levels; it means they add another layer of harm on top. The evidence we’ve reviewed leans toward this explanation: it’s not more amyloid or tau causing faster decline, but the extra burden from Lewy body proteins. There are no studies in our analysis that contradict this. For someone living with or caring for a person with Alzheimer’s, this means that even if Lewy bodies are present, the treatment focus might still need to address both types of damage separately — not just the Alzheimer’s proteins. It’s about managing the full picture, not assuming one disease is making the other worse at the protein level.