This article is about the psychological phenomenon. For the album, see Sundowning (album).

Sundowning, or sundown syndrome[1] 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.[2][3][4] 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.[2][3] Research shows that 20–45% of Alzheimer's patients will experience some sort of sundowning confusion.[2]


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.

Disturbances in circadian rhythms

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).[4] 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.

Another cause can be oral problems, like tooth decay with pain. When the time a meal is served comes close, a patient can show symptoms of sundowning. This cause is not widely recognized.[6]



  1. Khachiyants N, Trinkle D, Son SJ, Kim KY (2011). "Sundown syndrome in persons with dementia: an update". Psychiatry Investig. 8: 275–87. doi:10.4306/pi.2011.8.4.275. PMC 3246134Freely accessible. PMID 22216036.
  2. 1 2 3 4 5 6 7 8 9 Smith, G. (April 28, 2011). "Sundowning: Late-day confusion". Mayo Clinic. Retrieved August 30, 2016.
  3. 1 2 3 4 5 6 7 8 9 Alzheimer's Association, "Sleeplessness and Sundowning.", 2011. Web. 14 May 2012.
  4. 1 2 3 de Jonghe A; Korevaar J. C; Munster B. C Van (2010). "Effectiveness of melatonin treatment on circadian rhythm disturbances in dementia. Are there implications for delirium? A systematic review". International Journal of Geriatric Psychiatry. 25 (12): 1201–08. doi:10.1002/gps.2454.
  5. Keller, S. "Sundowning." WebMD. WebMD LLC, 2012. Web. 14 May 2012.
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