[Early diagnosis and prevention of dementia in the aged].

From the view point of prevention and treatment of dementia, dementia can be classified into three main groups. The first is treatable or preventable dementia. Unfortunately, this group occupies only 10 or 20% of all demented patients. However, early diagnosis and treatment of diseases belonging to this group are particularly important. The other two groups are Alzheimer-type dementia (ATD) and vascular dementia. Early diagnosis of ATD is still rather difficult. We recently have found that alpha 1-antichymotrypsin (alpha 1-ACT) increases significantly in the serum and cerebrospinal fluid in ATD. Thus, alpha 1-ACT can be used as an antemortem biological marker of ATD. Positron emission CT (PET) is also useful for the early diagnosis of ATD, because decrease in CMRO2 in the unilateral temporo-parietal region occurs in a relatively early stage of this disease. On the other hand, vascular dementia can be said to be becoming one of the treatable or preventable dementias. Vascular dementia is mainly based on cerebral infarction. Therefore, prevention of initial stroke is most essential. For this purpose, correction of risk factors and use of antiplatelet agents in those cases suffering a transient ischemic attack or subjective symptoms are necessary.