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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 other forms of 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][5]


Symptoms are not limited to but may include:

  • Increased general confusion as natural light begins to fade and increased shadows appear.[2][6]
  • Agitation and mood swings. Individuals may become fairly frustrated with their own confusion as well as aggravated by noise. Individuals found yelling and becoming increasingly upset with their caregiver is not uncommon.[2][3]
  • Mental and physical fatigue increase with the setting of the sun. This fatigue can play a role in the individual's irritability.[2][3]
  • Tremors may increase and become uncontrollable.[citation needed]
  • An individual may experience an increase in their restlessness while trying to sleep. Restlessness can often lead to pacing and or wandering which can be potentially harmful for an individual in a confused state.[3]


While the specific causes of sundowning have not been empirically proven, some evidence suggests that circadian rhythm disruption increases sundowning behaviors. In humans, sunset triggers a biochemical cascade that involves a reduction of dopamine levels and a shift towards melatonin production as the body prepares for sleep. In individuals with dementia, melatonin production may be decreased,[7] which may interrupt other neurotransmitter systems.

Sundowning should be distinguished from delirium, and should be presumed to be delirium when it appears as a new behavioral pattern until a causal link between sunset and behavioral disturbance is established. Patients with established sundowning and no obvious medical illness may be suffering from impaired circadian regulation, or may be affected by nocturnal aspects of their institutional environment such as shift changes, increased noise, or reduced staffing (which leads to fewer opportunities for social interaction).

Disturbances in circadian rhythms[edit]

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 SCN 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 analyse this disruption properly. By the time an Alzheimer's patient has died, they have usually surpassed the level of brain damage (and associated dementia) 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,[8] however anticipation of food can increase dopamine levels, and dopamine and melatonin have an antagonistic relationship.


  • If possible, a consistent sleeping schedule and daily routine that a sufferer is comfortable with can reduce confusion and agitation.[2]
  • If the patient's condition permits, having increased daily activity incorporated into their schedule can help promote an earlier bed time and need for sleep.[2][3]
  • Check for over-napping. Patients may wish to take naps during the day, but unintentionally getting too much sleep will affect nighttime sleep. Physical activity is a treatment for Alzheimer's, and a way to encourage night sleep.[3]
  • Caffeine is a (fast-working) brain stimulant, but should be limited at night if a night's sleep is needed.[2][3]
  • Caregivers could try letting patients choose their own sleeping arrangements each night, wherever they feel most comfortable sleeping, as well as allow for a dim light to occupy room to alleviate confusion associated with an unfamiliar place.[3]
  • Some evidence supports the use of melatonin to induce sleep.[4]


  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 3246134. PMID 22216036.
  2. ^ a b c d e f g h i Smith, G. (April 28, 2011). "Sundowning: Late-day confusion". Mayo Clinic. Retrieved August 30, 2016.
  3. ^ a b c d e f g h i "Sleeplessness and Sundowning". Alzheimer's Association.
  4. ^ a b c 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. ^ "Il demente e la sindrome del tramonto" [The demented and the sunset syndrome]. (in Italian). April 2, 2014.
  6. ^ Keller, S. "Sundowning." WebMD. WebMD LLC, 2012. Web. 14 May 2012.
  7. ^ Khachiyants N, Trinkle D, Son SJ, Kim KY (2011). "Sundown syndrome in persons with dementia: an update". Psychiatry Investigation. 8 (4): 275–87. doi:10.4306/pi.2011.8.4.275. PMC 3246134. PMID 22216036.
  8. ^ Erik Scherder. "Waarom vernietigt vanillevla onze hersenen? - Universiteit van Nederland" [Why does vanilla custard destroy our brains?].