Sundowning, or sundown syndrome,[1] is a neurological phenomenon associated with increased confusion and restlessness in people with delirium or some form of dementia. It is most commonly associated with Alzheimer's disease but also found in those with other forms of dementia. The term "sundowning" was coined by nurse Lois K. Evans in 1987 due to the timing of the person's increased confusion beginning in the late afternoon and early evening.[2][3] For people with sundown syndrome, a multitude of behavioral problems begin to occur and are associated with long term adverse outcomes.[4][5][6][7] Sundowning seems to occur more frequently during the middle stages of Alzheimer's disease and mixed dementia and seems to subside with the progression of the person's dementia.[4][5] People are generally able to understand that this behavioral pattern is abnormal. Research shows that 20–45% of people with Alzheimer's will experience some variation of sundowning confusion.[4][8] However, despite lack of an official diagnosis of sundown syndrome in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), there is currently a wide range of reported prevalence.[2]
The following social, economic, and physiological adverse outcomes are correlated with individuals affected by sundowning and their caregivers:
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.[11] 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,[1] which may interrupt other neurotransmitter systems.
Other causes or precipitating factors that may lead to sundown syndrome may include hormonal changes, disturbances in REM sleep, individual and/or caregiver fatigue, inappropriate medication use, or being predisposed to behavioral disorders from chronic neurological diseases.[12] Resources in an institution's environment can also play a role as a symptom trigger. A reduced number of staff in the evening can attribute to more unmet needs and a lower threshold for agitation for individuals with sundown syndrome.[13]
Sundowning should be distinguished from delirium, and could be presumed to be delirium when it appears as a new behavioral pattern until a causal link between sunset and behavioral disturbance is established.[14] People 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). Delirium is generally an acute event that can span over a time period of hours to days.[1]
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).[6] The SCN is located in the hypothalamus and 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 analyze this disruption properly. By the time a person experiencing Alzheimer's 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. The pineal gland produces melatonin when signaled by the SCN to help maintain circadian rhythms. Melatonin supplementation can be administered to older adults as their natural hormonal production decreases over time.[12]
Another cause can be oral problems, like tooth decay with pain. When the time a meal is served comes close, a person can show symptoms of sundowning. This cause is not widely recognized;[15] however, anticipation of food can increase dopamine levels, and dopamine and melatonin have an antagonistic relationship.
Serotonin has also been observed to potentially have a key role in the regulation of circadian rhythm as research has shown that serotonergic agonism in the SCN results in "phase shifts" in portions of the light-dark cycle.[2][16][17] In addition to the effects on circadian rhythm, serotonin is also known to be involved in the regulation of aggression.[2] Due to the serotonergic signaling deficiencies of Alzheimer's disease, it has been commonly reported that deficiencies in serotonin have been associated with worsening circadian rhythm or aggression.[2][18]
Elderly people often experience multiple comorbidities that may contribute to the phenomenon of sundowning syndrome through neurodegeneration.
Treatment of sundown syndrome may vary based upon when agitated behavior is observed throughout the day.[21]
There are several pathways in the pipeline for scientists seeking therapeutic options for sundowning syndrome.
In addition to sundown syndrome not being officially recognized in the DSM-5, there is also the thought that sundown syndrome may be a phenomenon of caretakers' perception of patient agitation in the early afternoon to evening.[2] Some studies have observed sundown syndrome occurring at times other than sunset which may suggest the symptoms associated with sundown syndrome are time-dependent rather than occurring specifically at sundown.[2][31]