The Spectrum Series: Grappling with the Overlap between Alzheimer's and Parkinson's Diseases

Sometimes in science, a concept lingers unattended in the collective back of researchers' minds for years; they sense there is something important to it but are not ready to grasp it head-on. Then something changes and, voila, the concept moves front and center. Such was the case with the issue of overlap in the major neurodegenerative diseases at the 9th International Conference AD/PD held 11-15 March in the Czech capital city of Prague. Previous AD/PD conferences had reflected the de-facto separation in the daily work of most scientists and clinicians in this field. Even though they spent days under the same roof, by and large the movement disorder people went to one meeting and the dementia people to another. But Prague was different. Rather than being treated as an inconvenient side issue that blurred boundaries, the extensive and multitudinous overlap between Alzheimer and Parkinson diseases (and also the frontotemporal dementias) was the focus of presentations and hallway discussion. Much of the buzz about this topic had spilled over into Prague from a preceding workshop in the former Royal German city of Kassel that had focused on dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD). These are two underappreciated conditions that occupy a large area of overlap between AD and PD. From 8-10 March, co-organizer Brit Mollenhauer