What Is Sundown Syndrome?

  • Alessia ZappaIntegrated Masters, Biomedical Sciences, University of York

If you have a loved one who suffers from Alzheimer’s disease or another type of dementia, have you ever noticed whether they exhibit anxious feelings as the sun starts to set? If the answer is yes, they could have a condition called sundown syndrome, also known as sundowning or late-day confusion. This term refers to a group of confused and paranoid behaviours and thoughts that people who have dementia can experience, usually in the late afternoon and lasting into the night (hence the name “sundown”).1 

This article will describe the variety of symptoms and triggers of sundowning, as well as who is more at risk of developing this syndrome, and which treatments are used to help alleviate these anxious behaviours and feelings.

Symptoms of sundown syndrome

The following list outlines the vast range of symptoms a patient may feel, particularly in the evening and into the night. It is not said that a patient will feel all these characteristics listed below, but it is likely they’ll experience some of them:1 

  • Feeling agitated and restless 
  • Feeling confused and disoriented – including not knowing where they are and who other people are
  • Reduced attention levels
  • Violent and aggressive tendencies
  • Becoming unusually and increasingly demanding
  • Feeling increasingly irritable
  • Apathy (a lack of interest in anything, or a loss of interest in previous hobbies)
  • Changes in eating patterns and appetite
  • Intense feelings of sadness
  • Fear, paranoia and suspiciousness
  • Anxiety
  • Depression
  • Visual and auditory hallucinations
  • Sleep disturbances such as insomnia

Risk factors for sundown syndrome

There are certain factors that can increase a person’s chances of developing sundown syndrome. The primary one, as mentioned previously, is if someone already has some form of dementia – in fact, the majority of sundowning patients suffer from dementia.1 Around 20% of diagnosed Alzheimer’s patients experience such late-day confusion, typically those who are in the middle and late stages of the disease. Studies have shown that sundown syndrome could speed up the mental decline of a person with Alzheimer’s disease.1

In particular, people with Alzheimer’s disease who have a specific gene called the Apolipoprotein Eɛ4 (ApoEɛ4) have a higher risk of developing sundown syndrome.2 ApoE is a protein that is produced in the brain and plays an important role in the regulation of normal, healthy processes and connections between the cells of the brain (neurons).3

However, the ɛ4 version of this protein is the strongest risk factor for developing Alzheimer’s disease, as it effectively helps the formation of the signature sticky plaques (known as beta-amyloid) found in the brains of patients, which cause neurons to die and leads to Alzheimer’s symptoms.4 Hence, having this gene not only increases the risk of developing Alzheimer’s disease but also subsequent sundown syndrome.

Other medical conditions that can contribute to the risk of developing sundowning in dementia patients include:1

Besides these medical conditions being risk factors for sundowning, old age can also make people more prone to developing the syndrome. The older a person gets, the more at risk they become of developing a form of dementia, and as previously mentioned, dementia in turn increases the risk of developing sundown syndrome.1 

Triggers for sundown syndrome

The cause of sundown syndrome remains unknown.1 However, there are various factors that have been shown to trigger the symptoms of sundown syndrome.

Disruption of our circadian cycle – the body’s “internal clock”

One of the most studied triggers for the development of sundown syndrome is the degeneration of a small part of the brain called the suprachiasmatic nucleus, found in the part of the brain called the hypothalamus.5 This part of the brain is what is referred to as the “biological internal clock” of our body, as it is responsible for an essential process called the circadian rhythm. This cycle is the physical, behavioural and mental changes that each human goes through during a 24-hour period; natural changes which occur due to our cells and organs responding to the light and dark throughout the day.

One important role of this cycle is to help make us feel sleepy at night – this is done by the suprachiasmatic nucleus signalling your brain’s pineal gland to produce and release a hormone called melatonin, in response to the dark. Melatonin is responsible for making us feel tired and helping us fall asleep.5 

Melatonin levels decrease with age and are particularly reduced in patients with Alzheimer’s and other dementia types. Moreover, dementia patients can also experience the degeneration of their suprachiasmatic nucleus.6

Hence, the degradation of this important part of the brain and the decreased levels of melatonin lead to disturbances in the circadian cycle, and these disturbances in turn can trigger the symptoms of sundown syndrome in Alzheimer’s patients. This can lead to disrupted sleep and/or the development of sleep disorders associated with sundowning.7 


If a patient is on medication to help treat their dementia symptoms, this unfortunately can have adverse effects and make them feel more agitated and restless at night and cause insomnia symptoms associated with sundowning.8

Other triggers

Other potential triggers of sundown syndrome in dementia patients include the following:1 

  • Being dehydrated or hungry
  • Being overstimulated by a busy day
  • Too little light exposure throughout the day
  • A lack or loss of a routine
  • Spending a day in an unfamiliar place
  • Developing an infection

Diagnosis of sundown syndrome

There are no formal criteria for a diagnosis of sundown syndrome, due to how varied the symptoms of this disorder can be. Hence, this can make diagnosis of the syndrome quite difficult.1

The diagnosis of sundowning is purely clinical – a doctor will assess the symptoms of the patient via a physical examination and questions, and take their medical history to assess whether their sundown syndrome can be connected to other medical conditions.1 

Differential diagnosis of sundown syndrome and delirium

It can sometimes be difficult to distinguish between sundown syndrome and delirium, which is defined as a state of sudden confusion and change in a person’s mental function. This is because both sundowning and delirium patients can experience similar agitated and confused behaviours. However, the difference is duration. Delirium tends to be sudden, temporary, and fluctuates throughout the day. Sundown syndrome, on the other hand, is ongoing and becomes more pronounced as the sun sets.1 

Management and treatment of sundown syndrome

Although there is no cure for sundown syndrome, there are various treatments and management techniques which can be used, all of which aim to help alleviate symptoms patients may feel, ensuring the person does not live in fear at night time or accidentally injure themselves or others.1 

Non-pharmacological interventions

Non-pharmacological (non-drug) management is advised before any sort of pharmacological (drug) therapy is attempted.1 

1. Routine and structure

Ensuring there is a routine and structure to a patient’s day and night helps them feel more settled and less anxious. Examples of things to do to help structure a sundown syndrome patient’s day include:1

  • Limiting caffeine and sugar intake to the morning hours
  • Limiting naps during the day
  • Planning outside activities during the day, allowing the patient to be exposed to daylight
  • If they must go to a new, unfamiliar place, the patient can bring familiar items (such as photographs) to help them feel more relaxed and prevent overstimulation
  • Taking evening walks to reduce restlessness before bed
  • Finding relaxing activities to do during the time of day that they usually experience symptoms
  • Low light exposure during the evening and whilst preparing for bed (e.g. no phones or TV screen time)
  • Reducing stimulating background noise in the evening (e.g. loud noises from the TV, or loud conversations)
  • Setting and practising good sleep habits (getting ready for bed and going to bed at the same time and same place every night)

2. Light therapy

Light therapy consists of exposing the patient to direct sunlight during the day, or artificial light at controlled wavelengths at a calculated distance which mimics outdoor light. The exposure to light induces chemical changes in the brain that help the patient feel less confused and agitated, as well helping to improve their sleep quality.9 

3. Music therapy

Music therapy draws on the relationship the patient may have with certain sounds and styles of music to help them feel more relaxed and less anxious.10 

4. Aromatherapy

Aromatherapy uses essential oils and other plant compounds to help promote patients’ feelings of well-being and calm their anxious and fearful thoughts.11 

5. Caregiver education

Caregivers of patients with sundown syndrome and dementia should be educated on the disorder, to know what they can do to help their patient. Caregivers should also listen to their patients to try to understand what is specifically triggering their sundowning symptoms, in order to help alleviate them. For instance, if the patient’s agitation is due to being hungry, then offering a snack can ease their symptoms and reduce any behavioural disruptions.

Any of these non-pharmacological treatments can also be used to try to help prevent someone from developing sundown syndrome.1 

Pharmacological interventions

If non-pharmacological (non-drug) interventions do not work, then symptoms of sundowning can also be treated with medications.

1. Melatonin

As mentioned previously, melatonin is the naturally-occurring hormone that is released during the night which helps us feel sleepy. In certain sundown syndrome patients with dementia, their melatonin secretion (release) levels can be low, playing a role in making them feel panicked and alert at night. Hence, these patients can take melatonin as oral medication, helping them sleep better, as well as helping reduce any nocturnal agitated behaviours.12 

2. Other medications

Other types of medications patients can take to alleviate symptoms include:

  • Low-potency antipsychotics – The most widely used medication to help sundowning symptoms, specifically to help hallucinations. However, these should be used with caution, as they have a long-term risk of stroke1
  • Antidepressant medications1 
  • Anti-anxiety medications1 
  • Hypnotics – These are used to induce, extend, and improve the quality of sleep of patients, and to reduce disturbances during sleep13 

Sundown syndrome patients should not be given pharmacological treatments without first consulting with a doctor, in order to discuss all possible side effects and come up with a personalised, suitable treatment plan. If a patient’s symptoms worsen when taking the medication, then adjustments or discontinuation of medication must be made.1 


Sundown syndrome, also known as sundowning and late-day confusion, is a disorder that primarily affects people with dementia, causing anxious and possibly aggressive behavioural changes in the late afternoon into night. Symptoms include confusion, anxiety, sadness and aggression. Although there is limited data on the syndrome itself, and there is no cure, there are various non-pharmacological and pharmacological treatments that can be used in order to manage someone’s symptoms. However, a doctor must be consulted before any medication is used. 


  1. Khachiyants N, Trinkle D, Son SJ, Kim KY. Sundown syndrome in persons with dementia: an update. Psychiatry Investig [Internet]. 2011 Dec [cited 2023 Oct 12];8(4):275–87. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3246134/
  2. Todd WD. Potential pathways for circadian dysfunction and sundowning-related behavioral aggression in Alzheimer's disease and related dementias. Front Neurosci [Internet]. 2020 Sep 3 [cited 2024 Feb 16];14:910. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7494756/
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  4. Kim J, Basak JM, Holtzman DM. The role of apolipoprotein e in alzheimer’s disease. Neuron [Internet]. 2009 Aug 13 [cited 2023 Oct 12];63(3):287–303. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3044446/
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  7. Menegardo CS, Friggi FA, Scardini JB, Rossi TS, Vieira TDS, Tieppo A, et al. Sundown syndrome in patients with Alzheimer’s disease dementia. Dement neuropsychol [Internet]. 2019 Dec [cited 2024 Apr 4];13(4):469–74. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1980-57642019000400469&tlng=en
  8. Rogers SL, Doody RS, Mohs RC, Friedhoff LT, and the Donepezil Study Group. Donepezil improves cognition and global function in alzheimer disease: a 15-week, double-blind, placebo-controlled study. Archives of Internal Medicine [Internet]. 1998 May 11 [cited 2024 Feb 19];158(9):1021–31. Available from: https://doi.org/10.1001/archinte.158.9.1021
  9. Hanford N, Figueiro M. Light therapy and alzheimer’s disease and related dementia: past, present, and future. JAD [Internet]. 2013 Jan 21 [cited 2024 Apr 4];33(4):913–22. Available from: https://www.medra.org/servlet/aliasResolver?alias=iospress&doi=10.3233/JAD-2012-121645
  10. Moreno-Morales C, Calero R, Moreno-Morales P, Pintado C. Music therapy in the treatment of dementia: a systematic review and meta-analysis. Front Med (Lausanne) [Internet]. 2020 May 19 [cited 2023 Oct 12];7:160. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7248378/
  11. Li BSY, Chan CWH, Li M, Wong IKY, Yu YHU. Effectiveness and safety of aromatherapy in managing behavioral and psychological symptoms of dementia: a mixed-methods systematic review. Dementia and Geriatric Cognitive Disorders Extra [Internet]. 2021 Dec 2 [cited 2024 Feb 16];11(3):273–97. Available from: https://doi.org/10.1159/000519915
  12. Asayama K, Yamadera H, Ito T, Suzuki H, Kudo Y, Endo S. Double blind study of melatonin effects on the sleep-wake rhythm, cognitive and non-cognitive functions in alzheimer type dementia. J Nippon Med Sch [Internet]. 2003 [cited 2024 Apr 4];70(4):334–41. Available from: http://www.jstage.jst.go.jp/article/jnms/70/4/70_4_334/_article
  13. Duckett S. Managing the sundowning patient. Journal of Rehabilitation; Washington, D.C. [Internet] Jan 1, 1993 [cited 2023 Oct 12]; 59(1):24. Available from: https://www.proquest.com/openview/89805bfbbdd45d6c98a19d555db6f85c/1?pq-origsite=gscholar&cbl=1819158
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Alessia Zappa

Integrated Masters, Biomedical Sciences, University of York

Alessia (bilingual in both English and Italian) has recently graduated from the University of York with a Master of Biomedical Science in Biomedical Sciences. Throughout her degree, she has had significant practice in a variety of written communication styles – from literature reviews, grant proposals, laboratory reports, to developing a series of science revision activities aimed for 12-13 year olds. She also has had extensive experience in collecting data, both within a laboratory setting (particularly in cell culture experiments) and online through survey-based projects. She has a particular passion for cancer research and immunology, with her final year project focusing on how the immune cell macrophage can be manipulated in order to target melanoma.

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