Sundowning typically begins during the middle stages of dementia and often continues into the later stages. It affects roughly 20% to 50% of people with dementia, depending on the study, and is one of the most common reasons families seek nursing facility placement. Understanding when and why it happens can help you recognize what’s changing and respond effectively.
When Sundowning Typically Appears
Sundowning begins during the middle and later stages of Alzheimer’s disease, according to the Cleveland Clinic, and usually persists as long as its underlying triggers remain. In practical terms, this means it tends to emerge after the early, mild stage, when memory loss is noticeable but daily functioning is still mostly intact. By the moderate stage, the brain changes driving sundowning have progressed enough to disrupt the body’s internal clock and make a person more vulnerable to confusion as the day wears on.
It does not typically appear out of nowhere in early-stage dementia. Most caregivers first notice it when their loved one is already experiencing significant difficulty with daily tasks, increased confusion, and personality changes. As the disease advances further into severe stages, agitation and aggression can worsen, and sundowning may intensify alongside that progression. However, in the very latest stages, when a person becomes largely immobile and unresponsive, the visible behavioral symptoms of sundowning often diminish simply because overall activity declines.
How Common Sundowning Is
Prevalence estimates vary widely, from as low as 14% to over 60%, largely because sundowning lacks a single standardized definition. A 2022 review pooled data from multiple studies and found that roughly 49% of people with dementia experience it. An Italian study of 184 Alzheimer’s patients identified sundowning in about 21%, while other research groups have reported rates above 40%. The variation comes down to how researchers define it, whether they rely on caregiver reports or direct observation, and how severe the dementia is in the group being studied. People with more advanced cognitive decline, older age, and existing sleep problems consistently show higher rates. Some research also suggests sundowning is more prevalent among women.
What Sundowning Looks Like
Sundowning is not a single behavior. It is a pattern of worsening confusion, agitation, or emotional distress that emerges in the late afternoon or early evening. A person who was relatively calm during the morning may become restless, anxious, irritable, or aggressive as daylight fades. Some people pace, others yell or cry, and some try to leave the house. Increased suspicion, hallucinations, and resistance to help with routine tasks like bathing or getting ready for bed are also common.
Episodes can last minutes or hours. They tend to follow a rough daily pattern, though the severity can fluctuate from day to day depending on how tired the person is, how much stimulation they experienced earlier, and whether they are in pain or dealing with an underlying illness.
Why It Happens in the Evening
The brain has an internal clock that coordinates sleep, wakefulness, body temperature, and hormone release on a roughly 24-hour cycle. This clock sits in a tiny brain region that receives light signals directly from the eyes. In Alzheimer’s disease, this region deteriorates. The nerve cells that produce key signaling chemicals shrink in number, and the energy metabolism within the area breaks down. At the same time, the light-sensing cells in the retina that feed information to the brain’s clock also degrade.
The result is that the brain loses its ability to distinguish daytime from nighttime reliably. Body temperature rhythms shift, the sleep hormone melatonin is released at the wrong times or in insufficient amounts, and the normal evening wind-down process goes haywire. Instead of feeling naturally sleepy as the sun sets, a person with moderate or advanced dementia may feel disoriented and agitated.
This biological vulnerability is then amplified by environmental factors. Fading daylight creates low lighting and longer shadows, which can be confusing or even frightening to someone with impaired perception. A full day of activity leads to mental and physical fatigue, lowering the threshold for irritability. In care facilities, the late afternoon shift change around 3:00 PM brings more noise and less one-on-one attention. At home, caregivers themselves are often tired by evening, which can subtly change the emotional tone of interactions. Even unmanaged pain from conditions like arthritis tends to feel worse later in the day, adding another layer of distress.
Medications can contribute as well. Some drugs wear off by late afternoon, causing a rebound in symptoms. Others, particularly certain antidepressants and antipsychotics, can cause restlessness or involuntary movements as side effects that may be mistaken for, or worsen, sundowning.
How Light Therapy Can Help
Because the brain’s internal clock depends on light signals, bright light exposure is one of the most studied non-drug interventions for sundowning. Morning light therapy, typically using a light box delivering 2,500 to 10,000 lux for 30 minutes to two hours, has been shown to reduce evening agitation, improve nighttime sleep, and increase daytime wakefulness. Studies consistently find morning exposure more effective than afternoon sessions.
One study using 10,000 lux of late-morning light for two weeks showed measurable improvements on standard agitation scales. Another found that 30 minutes of morning light at 10,000 lux reduced agitation scores significantly. A third compared morning and afternoon bright light at 2,500 lux and found that while both helped, morning exposure produced better results for agitation, depression, and restless movement.
At night, the goal shifts from brightness to strategic low-level lighting. LED strips placed around doorframes and along hallways to the bathroom (providing about 5 to 10 lux) can help a disoriented person navigate without the confusion that total darkness or a single dim nightlight creates. These strips outline the shape of the room and pathways, giving visual cues that reduce falls and anxiety during nighttime waking.
Practical Strategies for Caregivers
Managing sundowning is largely about controlling the triggers you can control. Keep the late afternoon and evening calm and predictable. Reduce noise, turn on lights before sunset so there is no sudden dimming, and avoid scheduling demanding activities or outings for the second half of the day. A consistent daily routine, with more stimulating activities in the morning and quieter, structured wind-down time in the afternoon, helps reduce the fatigue that fuels evening agitation.
Limit caffeine and sugar after the morning. If possible, encourage a short rest (but not a long nap) in the early afternoon. Close curtains before sunset to eliminate confusing shadows, and keep rooms evenly lit rather than relying on a single lamp that creates dark corners. If the person becomes agitated, speak slowly and calmly, validate their feelings rather than arguing with confused perceptions, and gently redirect their attention. Playing familiar music, offering a simple snack, or going for a brief walk in a well-lit area can sometimes break the cycle.
Pay attention to pain. Someone with dementia may not be able to tell you they hurt, but grimacing, guarding a body part, or increased agitation at a consistent time of day can be clues. Addressing untreated pain often reduces sundowning episodes noticeably.
The Role of Melatonin
Because the brain’s natural melatonin production is disrupted in Alzheimer’s disease, supplemental melatonin has been tested in multiple studies with mixed but generally promising results. In several small trials, doses of 3 to 6 mg taken at bedtime reduced sundowning and improved sleep regularity. One long-term study followed 14 patients taking 6 to 9 mg nightly for two to three years and found that sundowning became undetectable in 12 of them over that period.
However, two larger placebo-controlled trials in institutionalized patients found no significant improvement in agitation or sleep from melatonin alone. A study comparing 2.5 mg slow-release melatonin, 10 mg immediate-release melatonin, and placebo over two months found that caregiver-rated sleep quality improved only in the slow-release group, suggesting that the formulation and timing matter. Melatonin appears most helpful when combined with other interventions like bright light therapy and consistent routines, rather than used in isolation.