Sundowning

Sundowning, or sundown syndrome is a neurological phenomenon associated with increased confusion and restlessness in patients with delirium or some form of dementia. Most commonly associated with Alzheimer's disease, but also found in those with mixed dementia, the term "sundowning" was coined due to the timing of the patient's confusion. For patients with sundowning syndrome, a multitude of behavioral problems begin to occur in the evening or while the sun is setting. Sundowning seems to occur more frequently during the middle stages of Alzheimer's disease and mixed dementia. Patients are generally able to understand that this behavioral pattern is abnormal. Sundowning seems to subside with the progression of a patient's dementia. Research shows that 20–45% of Alzheimer's patients will experience some sort of sundowning confusion.

Symptoms are not limited to but may include:

While the specific causes of sundowning have not been empirically proven, some evidence suggests that circadian rhythm disruption increases sundowning behaviors. It is a frequently seen but poorly understood phenomenon of behavioral deterioration in the evening hours, most commonly in demented, institutionalized patients. Sundowning should be distinguished from delirium, and should be presumed to be delirium when it is a new pattern. Patients with established sundowning and no obvious medical illness may be suffering the effects of impaired circadian regulation, or be affected by nocturnal factors in the institutional environment, such as shift changes, noise, and reduced staffing.

It is thought that with the development of plaques and tangles associated with Alzheimer's disease there might be a disruption within the suprachiasmatic nucleus (SCN). The suprachiasmatic nucleus is associated with regulating sleep patterns by maintaining circadian rhythms, which are strongly associated with external light and dark cues. A disruption within the suprachiasmatic nucleus would seem to be an area that could cause the types of confusion that are seen in sundowning. However, finding evidence for this is difficult, as an autopsy is needed to definitively diagnose Alzheimer's in a patient. Once an Alzheimer's patient has died, they have usually surpassed the level of dementia and brain damage that would be associated with sundowning. This hypothesis is, however, supported by the effectiveness of melatonin, a natural hormone, to decrease behavioral symptoms associated with sundowning.

...
Wikipedia