Sundown Syndrome · What It Is, Causes, Signs and Symptoms, Diagnosis, and More

The exact mechanisms of sundown syndrome are poorly understood, however, it is thought to be a complex interplay between various factors including neurobiological and physiological disruptions, underlying medical conditions, environmental factors, and medications.  

In terms of neurobiological factors, alterations in neurotransmitters such as acetylcholine (i.e., which is abnormally low in dementia) and melatonin levels may influence the individual’s circadian rhythm and alter their body clock. These neurotransmitter imbalances and alterations may contribute to sundowning.  

Unmet physiological needs, like hunger, fatigue, or needing the bathroom may not be expressed clearly, leading to agitation which could exacerbate sundown syndrome. Underlying medical conditions like insomnia and uncontrolled pain may also contribute to irritability and agitation. As natural light fades, visual perception can worsen, creating misinterpretations of surroundings and increasing confusion or fear.  

Additionally, other environmental factors like overstimulation during the day or complete boredom could make someone more agitated in the evening. Some individuals may pick up on staff or family caregiver changes in the evening, which can increase anxiety or insecurity.    

Finally, some of the medications used to manage symptoms like anxiety, agitation, depression, psychosis, or sleep problems can unintentionally worsen sundowning or other behavioral symptoms, especially if not used carefully. These medications include antipsychotics (e.g., haloperidol), anticholinergics (e.g., donepezil, diphenhydramine), and benzodiazepines (e.g., diazepam, lorazepam).  

Diagnosis of sundown syndrome is clinical and begins with a thorough review of symptoms and medical history that is often obtained from family members or caregivers depending on the stage of dementia. This involves careful observation and documentation of the individual’s behaviors throughout the day, with a focus on the late afternoon, evening, and night hours. Cognitive questionnaires (e.g., mini-mental state exam or MMSE) may be administered to evaluate the individual’s cognitive function and to diagnose or assess the progression of dementia. Other diagnoses may present with similar symptoms, such as depression and sleep disorders, therefore a pertinent history related to mood symptoms, changes in habits and routines, and sleep patterns should be elicited.  

While routine laboratory tests are not required for diagnosis, they can help exclude underlying conditions that may mimic sundowning behaviors, such as a urinalysis to exclude urinary tract infections. If the individual is presenting for the first time with sundowning behaviors, a dementia work-up can be pursued to exclude reversible causes (e.g., vitamin B12, thyroid function tests, HIV screening). Neuroimaging (e.g., computed tomography or magnetic resonance imaging) may not be required but can be helpful when excluding neurologic conditions like a stroke or a brain tumor. The diagnosis is made when a temporal pattern of characteristic behaviors is established in conjunction with a known history of dementia and secondary causes (e.g., infection, medications, brain lesions) are excluded.  

There is currently no cure for sundown syndrome and treatment consists of a multidisciplinary approach that is aimed at slowing the progression of dementia, reducing neuropsychiatric symptoms, and improving the individual’s quality of life.   

Individuals diagnosed with dementia can be initiated on medications aimed at slowing the progression of the disease. Early and middle-stage dementia can initially be treated with anticholinergics (e.g., donepezil), while NMDA-receptor antagonists (e.g., memantine) may be indicated for more advanced stages. Measures should be taken to reduce polypharmacy and to titrate dementia medication doses appropriately, as they may also cause side effects that could exacerbate symptoms of sundowning.  

Non-pharmacological ways to prevent sundowning include maintaining a consistent daily routine and sleep schedule, as well as avoiding naps during the day. Exposure to natural light during the mornings can help support healthy sleep-wake cycles, whereas creating a calm and familiar environment in the evenings may reduce anxiety. Activities like listening to soothing music, gentle stretching, watching familiar TV shows, or spending quiet time with a familiar caregiver can also reduce restlessness.