[Dementia--causes, diagnosis, treatment, and care]

The prevalence of dementia in the elderly (65 years old and over) was estimated at 6.3% (men 5.8%, women 6.7%) in Japan in 1985. Epidemiological studies done in several prefectures in 1989 and later showed a tendency for patients with Alzheimer's disease (AD) to outnumber those with vascular dementia (VD); the VD/AD ratio was less than 1.0 in over half of the surveys. A pathologic study (Kosaka 1996) of 79 patients with dementia revealed that AD was more common than VD, although clinical diagnoses were the reverse, which indicated that VD is still overdiagnosed in Japan. Diffuse Lewy body disease was observed in 15% of those patients without correct clinical diagnosis. Many biological markers for AD have been reported. We used 1H-magnetic resonance spectroscopy of the brain and found that the ratio of N-acetyl aspartate to creatine in AD patients was significantly smaller than that in age-matched controls without dementia. Based on genetic studies, AD is classified into five types. These are related to chromosomes 14 (presenilin-1), 21 (beta APP gene), 1 (presenilin-2), 19 (epsilon 4 alleles), and other. The causes of most sporadic cases remain unclear. Tacrine is the only drug authorized in the U.S.A. for treatment of AD, but it is not used in Japan because of its side effects. Many other drugs to treat dementia are now in nationwide clinical trials although only four are in phase III. Therefore, rehabilitation therapy is mandatory and details of that therapy should be individualized. A new system of public insurance for nursing care may be implemented by the government.