sundowning
noun
sun·down·ing
| \ ˈsən-ˌdau̇n-iŋ
\
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Medical Definition of sundowning
: a state of increased agitation, confusion, disorientation, and anxiety that typically occurs in the late afternoon or evening in some individuals affected with dementia
Sundowning is a major problem in the middle and late stages of disorders, such as Alzheimer's disease, that cause dementia.— Patricia N. Prinz et al., The New England Journal of Medicine, 23 Aug. 1990