A prodrome is an early set of non-specific symptoms that herald a particular disease. Here, researchers point to chronic inflammation as a prodrome of Alzheimer's (AD): "Recently, the term 'inflammaging' was coined [to] characterize a widely accepted paradigm that ageing is accompanied by a low-grade chronic up-regulation of certain pro-inflammatory responses. Inflammaging differs significantly the from [traditional] acute inflammation in that it is characterized by a relative decline in adaptive immunity ... While the over-active innate immunity characteristic of inflammaging may remain subclinical in many elderly individuals, a portion of individuals (postulated to have a "high responder inflammatory genotype") may shift from a state of "normal" or "subclinical" inflammaging to one or more of a number of age-associated diseases. ... Although conditions of enhanced innate immune response with overproduction of pro-inflammatory proteins are associated with both healthy aging and AD, it is suggested that those who age 'well' demonstrate anti-inflammaging mechanisms and biomarkers that likely counteract the adverse immunity of inflammaging. Thus, opposing the features of inflammaging may prevent or treat the symptoms of AD."

Link: http://www.ncbi.nlm.nih.gov/pubmed/19014446