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
