ビタミンB12・葉酸欠乏と認知症

Treatable Dementia due to Vitamin B12 and Folate Deficiency

「治せる認知症」の原因としてビタミン欠乏は頻度は稀ながら重要な課題である。とりわけ高齢者の認知症診療ではビタミンB₁₂欠乏が原因と考えられる症例に遭遇する頻度が高い。一方，葉酸はビタミンB₁₂と代謝経路上密接な関係を有し，その欠乏とビタミンB₁₂欠乏の間には共通点も多い。したがって本論では，ビタミンB₁₂欠乏と葉酸欠乏に焦点を絞り，これらの欠乏による認知症を診療するうえで必要な情報を概説する。

Abstract

Vitamin deficiency is one of the major causes of treatable dementia. Specifically, patients suffering from dementia frequentry display low serum levels of vitamin B₁₂. There is a close metabolic interaction between folate and vitamin B₁₂. Folate deficiency causes various neuropsychiatric symptoms, which resemble those observed in vitamin B₁₂ deficiency. This review summarizes, the basic pathophysiology of vitamin B₁₂ and folate deficiency, its clinical diagnosis, associated neuropsychiatric symptoms such as subacute combined degeneration and dementia, and epidemiological studies of cognitive decline and brain atrophy.