Sundown Syndrome

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The term sundown syndrome, also known as sundowning, refers to an increase in agitation during the late afternoon and evening hours in individuals with Alzheimers Disease and related dementias. Agitation is a class of behavior problems that include disruptive vocalization, physical aggression, and motor restlessness. This syndrome is said to affect between 10 and 37 percent of dementia patients. Although it is observed in both community and nursing-home settings, it appears to be more common in nursing homes.

Sundowning has entered the common parlance of dementia caregivers and many professionals; however, researchers have questioned whether sundowning is as common as assumed. Agitation does appear to be associated with various temporal factors in many dementia patients, including factors occurring in the late afternoon and evening. The few methodologically sound studies that have examined temporal patterns of agitation show that some nursing-home residents are predictably more likely to display agitation in the evening hours; other residents, however, show higher probabilities of occurrence in the morning, and still others show peaks of agitation during more than one time period in the day.

Further complicating the situation is the fact that the term agitation refers to a class of different behavior problems that range from simple pacing to physical aggression. Preliminary data suggest that some components of agitation (e.g., physical aggression) do occur more often during the late afternoon and evening hours, while repetitive requests for attention occur more often in the late morning and afternoon. Whether or not an individual demonstrates reliable temporal patterns of agitation depends on his or her sensitivity to physiological and environmental factors that can influence the occurrence of agitation during a twenty-four hour cycle.

One hypothetical cause of sundowning and other temporal patterns of agitation is a dysfunction of circadian rhythms. Neurological damage associated with dementia can, in itself, affect these rhythms, which have also been shown to be affected by the presence of light. Thus, factors such as the lack of exposure to natural light and an overexposure to artificial light during the evening can result in an increase in dementia patients activity level and, perhaps, agitation during the evening and nighttime. Another hypothesized cause of sundowning is frequent nighttime awakenings, which are common with aging and even more common in dementia. In addition to biological causes of nighttime awakening, researchers have found that staff in nursing homes awaken nursing-home residents frequently to check for urinary incontinence or to take vital signs. When awakened, dementia patients are more likely to have problems distinguishing reality from a dream-state. Thus, agitation at nighttime can be related to these frequent awakenings and the resulting disorientation. It has also been reported that fractured nocturnal sleep can result in more frequent agitation during the day. In addition, temporal patterns of agitation might be affected by the dosing schedule of the tranquilizing drugs sometimes used for the control of agitation. For example, if the drug is administered once in the morning and once in the evening, peaks in agitation can occur before the next dosage of the drug has taken effect.

A host of environmental factors have been posited as possible determinants of temporal patterns of agitation. Essentially, any environmental event that has a reliable temporal pattern can influence patient disruptive behaviors and produce temporally patterned agitation. The pattern reported by researchers of increased agitation for some dementia patients during both morning and evening time periods might be related to morning and evening care routines (e.g., dressing and bathing) conducted by staff at those times. Several researchers have reported higher frequencies of agitation during the three to five P.M. time period, which coincides with change-of-shift for nursing-home staff. It is thought that the increase in staff activity and general confusion during this time might be responsible for an increase in agitation for susceptible patients.

In summary, although there are sufficient data to suggest that some dementia patients display sundowning, the data are not sufficient to suggest that sundowning is a prevalent syndrome. A more accurate description is that agitation does show reliable temporal patterns in an unknown but marked number of dementia patients, particularly in nursing-home settings. These patterns have been related to both physiological (e.g., disruption of circadian rhythms) and environmental events that display temporal patterns and can influence the expression of agitation.

Discovering a reliable temporal pattern in a dementia patients display of agitation can be beneficial for treatment. For example, if agitation is linked with the dosing or scheduling of tranquilizing drugs, the dosage or scheduling can be changed so that agitation is less likely to occur. For residents who become particularly agitated during care routines, staff can be taught verbal and nonverbal communication skills that are less likely to affect a resident negatively, and consequently are less likely to result in agitation.

Louis D. Burgio Rachel Rodriguez

See also Dementia.


Bliwise, D. L. What is Sundowning? Journal of the American Geriatrics Society 42, no. 9 (1994): 10091011.

Evans, L. K. Sundown Syndrome in Institutionalized Elderly. Journal of the American Geriatrics Society 35, no. 2 (1987): 101108.

Gallagher-Thompson, D.; Brooks, J. O. I.; Bliwise, D.; Leader, J.; and Yesavage, J. A. The Relations among Caregiver Stress, Sundowning Symptoms, and Cognitive Decline in Alzheimers Disease. Journal of the American Geriatrics Society 40, no. 8 (1992): 807810.

Taylor, J. L.; Friedman, L.; Sheikh, J.; and Yesavage, J. A. Assessment and Management of Sundowning Phenomena. Seminars in Clinical Neuropsychiatry 2, no. 2 (1997): 113122.