Why Do Many People With Alzheimer's Experience Strong Mood Swings Late in the Day?

Many people with Alzheimer's experience a clinical phenomenon called "sundowning," or the emergence or worsening of neuropsychiatric symptoms like agitation, aggression, and disorientation in the late afternoon or early evening, reports the Washington Post . Some physicians suggest sundowning is related to reduced visibility that comes with darkness and shadows, or the shift change of hospital staff in the late afternoon; more recent studies imply a possible connection to disruption of the brain's suprachiasmatic nucleus (SCN), which regulates circadian rhythms. Investigations have shown the phenomenon's prevalence in 10 percent to 25 percent of those with moderate to severe dementia in nursing communities and up to 66 percent of people with Alzheimer's living at home. Its occurrence in some cognitively intact seniors also could be construed as a sign of approaching dementia. Circadian disruptions are one of the earliest symptoms observed in Alzheimer's, with such disturbances happening years before the emergence of more classical symptoms. Moreover, a recent study published in Nature Neuroscience found the SCN also regulates aggression. "This may mean that the body's internal clock regulates emotional patterns, and if you disrupt the circadian pathway that would keep that within the right timing, you can have really profound changes in behavior at certain times of the day," notes Harvard Medical School's William Todd.