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The amyloid hypothesis asserts that excess production or reduced clearance of the amyloid - beta ( A beta ) peptides in the brain initiates a sequence of events that ultimately lead to Alzheimer ' s disease and dementia .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None