::The two sources I added in my last edit (see quote above) were reviews: PMID 16687059 and PMID 18219824. There's another one: PMID 15493114. If the other numerous pathogenetic theories also have reviews, I don't see why we couldn't devote 2 sentences about them either. I wouldn't call the approach 'unusual', rather very useful. Although age may be a confounder, several primary sources establish an association in which that argument could not be used: PMID 18312403, PMID 15222691, PMID 11212132.