APOC3 and dementia: However, in a substudy of GEMS participants who remained free of clinical dementia, the amount of apoE in subspecies of HDL that contained or lacked apoC3 or apoJ was uniformly inversely associated with amyloid β deposition on positron emission tomographic scans.34 Thus, the amount of apoE, rather than the amount of apoA1, might be particularly strongly associated with dementia risk.