The present invention addresses the problem of providing a chemical agent for suppressing the progression of Alzheimer-type dementia and a method for suppressing the progression of Alzheimer-type dementia. 1-(3-(2-(1-benzothiophen-5-yl)ethoxy)propyl)azetidin-3-ol or a salt thereof has an effect of suppressing brain atrophy, and is useful as a prophylactic or therapeutic agent for brain atrophy. Thus, it is possible to prevent or treat brain atrophy observed in the aging process or in neurodegenerative diseases by administering 1-(3-(2-(1-benzothiophen-5-yl)ethoxy)propyl)azetidin-3-ol or a salt thereof.
