We will examine the mTBI patients in a long-term follow-up manner by cognitive tests and A-PET. This is a novel study for linking mTBI and AD by solid, reliable methods, in terms of A-PET and cognitive function tests. In addition, we will figure out the importance of APOE genotypes for amyloid accumulation and cognitive impairment. These results should shed light on the further clinical studies and amyloid-cleaning therapy for prevention and treatment for dementia after mTBI.