Sundowning typically starts in the late afternoon, often between 4:00 and 5:00 p.m., and can persist well into the night. The exact timing varies from person to person, but the pattern is consistent: as daylight fades, confusion and agitation rise. Up to 66% of people with dementia experience some form of sundowning, making it one of the most common behavioral challenges caregivers face.
Why Late Afternoon Is the Trigger Point
The brain has an internal clock, a small cluster of cells that keeps your sleep-wake cycle, body temperature, and hormone levels on a 24-hour schedule. In Alzheimer’s disease and other forms of dementia, this internal clock deteriorates. The damage is physical: the disease creates tangles and chemical changes in the part of the brain responsible for keeping rhythms synchronized with the outside world.
One measurable result is that the body’s temperature cycle shifts later in the day, a sign that internal timing has drifted out of alignment with the actual light-dark cycle. When the brain can no longer read environmental cues correctly, the transition from afternoon to evening becomes disorienting. The body doesn’t get the right signals about what time it is or what should happen next, and the result is a window of heightened confusion that typically opens as natural light starts to dim.
Hormonal Changes That Fuel the Timing
Two hormones play a central role. Melatonin, which normally rises in the evening to promote sleep, is produced at significantly lower levels in people with Alzheimer’s. Without that reliable signal, the brain loses one of its strongest cues for winding down. At the same time, cortisol (the body’s stress hormone) runs unusually high at night in dementia patients, when it should be dropping. The combination of too little calming signal and too much stress signal creates the perfect setup for evening agitation, anxiety, and restlessness.
These hormonal disruptions don’t just affect one evening. They feed a cycle: poor nighttime sleep caused by these imbalances can make the following day’s sundowning worse, which then disrupts sleep again.
What Sundowning Looks Like as It Begins
Sundowning doesn’t always arrive as a dramatic outburst. Early signs can be subtle. You might notice pacing, rocking in a chair, or “shadowing,” where the person follows their caregiver from room to room and won’t let them out of sight. Restlessness and irritability often come first, sometimes hours before the more intense symptoms set in.
As the episode progresses, behaviors can escalate to crying, yelling, or wandering. Emotionally, the person may express fear, deep sadness, or sudden anxiety that seems to come from nowhere. Confusion, paranoia, delusions, and hallucinations are all possible during a full sundowning episode. Not every person experiences all of these, and the pattern can change from day to day, which makes it especially difficult for caregivers to predict.
Environmental Factors That Make It Worse
The fading of natural light is the most obvious trigger, but it’s not the only one. Several environmental conditions can push sundowning earlier or make it more intense:
- Low or uneven indoor lighting. Shadows and dim corners can create visual confusion. Reflective surfaces like uncovered TV screens or mirrors can be particularly disorienting.
- Too little daylight exposure during the day. Without sufficient bright light earlier in the day, the brain’s already-damaged clock has even fewer cues to work with.
- Overstimulation. A noisy, busy household during the day can leave the person mentally exhausted by late afternoon, lowering their threshold for confusion.
Simple adjustments can help. Closing curtains before it gets dark outside removes the visual transition that often kicks off an episode. Keeping indoor lighting bright and even through the late afternoon smooths over the contrast between day and evening. Covering mirrors or TV screens when they’re not in use reduces unexpected reflections that can startle or confuse.
How Light Therapy Can Shift the Window
Because sundowning is rooted in a broken internal clock, one of the most studied interventions is bright light therapy. The goal is to give the brain a strong, consistent daytime signal that reinforces the difference between day and night.
The standard approach is 30 minutes of exposure to 10,000 lux from a full-spectrum light box, usually in the morning. The light should be placed at or above eye level, positioned about one to three feet away. If 10,000 lux isn’t available, lower intensities can work with longer sessions: 60 minutes at 5,000 lux or 90 minutes at 2,500 lux. Some people respond better to evening sessions, and others benefit from light exposure twice a day.
Light therapy won’t eliminate sundowning entirely, but consistent use can help stabilize the sleep-wake cycle enough to reduce the severity and delay the onset of evening symptoms.
Why the Timing Can Vary
While late afternoon is the most common starting point, the exact hour differs based on several factors. The season matters: in winter, when daylight fades earlier, symptoms can begin earlier too. The stage of dementia plays a role, since the brain structures governing circadian rhythm deteriorate further as the disease progresses. A person’s daytime activity level, sleep quality the night before, and even how much natural light they were exposed to during the day all influence when the window of confusion opens.
For caregivers tracking patterns, it helps to note the time agitation begins each day. Over a week or two, a consistent window usually emerges. Knowing that window lets you adjust the environment, lighting, and activity levels in advance rather than reacting once symptoms have already escalated.