Additional Study Information: The aim of this study is to understand the mechanisms of secondary effects of traumatic brain injury on the blood-brain barrier and to understand the biochemical differences in the blood of people with Alzheimer's disease and the volunteer group. We will compare biochemical blood differences between a healthy group and traumatic brain injury patients and Alzheimer's disease. Our aim is to identify biochemical changes in the blood that may worsen the prognosis in traumatic brain injury and Alzheimer's disease. We are looking for healthy volunteers in certain age groups (35-55, 60-80) who meet our eligibility criteria, such as not having a major illness. All you need to do is to come at the requested time and give blood only once. In return, we will give you 25 dollars (in form of a pay-card) for participating in the study.