Parkinson’s disease: signals, mechanisms, and uncertainty

Parkinson’s disease probably has multiple pathways. Real-world data can reveal associations worth testing, but observational findings must be separated from evidence that an intervention prevents or slows disease.

Start here

Read the evidence companion on tetanus–diphtheria vaccination and Parkinson’s disease. It covers the matched cohort, the progression signal, the proposed Clostridium tetani hypothesis, and the limitations that make prospective replication essential.

Questions this topic follows

• Can an old vaccine reveal a testable biological clue?
• Could gut or oral microbial exposures influence a subset of Parkinson’s disease?
• Which findings are associations, and which would require a randomized or prospective study?