Sundowning (dementia)

In medicine, sundowning, also known as sundown syndrome, is a syndrome involving the occurrence or increase of one or more abnormal behaviors in a circadian rhythm. Sundowning typically occurs during the late afternoon, evening, and night, hence the name. It occurs in persons with certain forms of dementia and psychosis, such as seen in Alzheimer's disease. Although not widely surveyed, sundowning is estimated to occur in 45% of persons diagnosed with Alzheimer's disease. A person who is sundowning may become abnormally demanding, suspicious, upset or disoriented, and see or hear things that are not there. After wandering, sundowning is the second most common type of disruptive behavior in institutionalized persons with dementia. Sundowning often co-occurs with wandering, and the combination of these two syndromes is an important contributing factor to an emergency situation: elopement at night. The cause of sundowning is unknown, but may be related to disturbed circadian rhythm.

Cause
Although the cause of sundowning is unknown, proposed causes include sensory deprivation from lower light conditions in the evening, and fatigue. Alzheimer's disease alters the normal daily cycle of changes in body temperature, and sundowning appears to be related to delay of those changes that normally occur in the evening. Contributing factors may include medications that can cause agitation or confusion, and sleep disorders.

Prognosis
In persons with early Alzheimer's disease, the presence of sundowning has been associated with faster decline in cognitive functions.

Treatment
Behavioural disturbance is often treated with antipsychotic medication such as haloperidol, risperidone, or olanzapine. However, these have significant side effects.