Sometimes, the symptoms occur quite late into the evening, said Dr. Victor Diaz, a neurologist at Orlando Health Neuroscience Institute. Approximately 1 in 5 people with dementia experience sundowning. It affects people with different forms of dementia, like Alzheimer's and Lewy body dementia, Diaz said. "Episodes can last anywhere from a few minutes to a few hours, and in some cases, can extend into the night."