Sundowning in dogs is a pattern of restlessness, confusion, and agitation that flares up in the evening or nighttime hours. It’s part of a broader condition called Cognitive Dysfunction Syndrome (CDS), the canine equivalent of dementia. Just as people with Alzheimer’s disease often become more disoriented as the sun goes down, older dogs with cognitive decline can pace, bark without reason, or wander aimlessly once evening arrives, even if they seemed relatively normal during the day.
CDS is common. One study found it affected 28% of dogs aged 11 to 12 and jumped to 68% of dogs aged 15 to 16. Sundowning is one of its most disruptive symptoms because it robs both the dog and the household of sleep, creating a cycle of exhaustion and worsening behavior.
What Happens in a Sundowning Dog’s Brain
The underlying cause is physical damage to the brain, not simply “getting old.” Dogs with CDS accumulate sticky protein deposits called beta-amyloid plaques throughout their cerebral cortex, the same type of plaque seen in human Alzheimer’s patients. These plaques interfere with normal brain signaling. Over time, the brain’s chemical messaging systems deteriorate: the system responsible for alertness and focus loses neurons, and the system involved in learning and memory shrinks measurably in cognitively impaired older dogs compared to healthy ones of the same age.
Alongside these chemical changes, the brain’s support cells become inflamed and swollen, adding further damage. The net result is a brain that increasingly struggles to process its environment, regulate emotions, and maintain a normal internal clock. That broken internal clock is what drives sundowning specifically. The circadian rhythm, which tells a dog when to sleep and when to be awake, loses its anchor. Dogs sleep more during the day, then find themselves alert, confused, and anxious when the house goes dark and quiet.
How Sundowning Looks at Home
Sundowning episodes typically begin in the late afternoon or early evening and can last well into the night. What you’ll see varies from dog to dog, but common behaviors include:
- Pacing and wandering: Walking the same path repeatedly, sometimes into corners or behind furniture where they get stuck.
- Vocalization: Barking, whining, or howling with no obvious trigger.
- Disorientation: Staring at walls, failing to recognize familiar people, or standing at the wrong side of a door waiting for it to open.
- Anxiety and clinginess: Following you from room to room, trembling, or seeming frightened by nothing in particular.
- Restlessness: Inability to settle, getting up and lying down repeatedly.
These episodes can be mild at first, maybe just some extra pacing a few nights a week. Over months, they tend to intensify and become nightly. Many owners initially mistake the behavior for pain, a need to go outside, or a reaction to a noise they can’t hear. The distinguishing feature of sundowning is its timing: the behavior clusters in the evening hours and follows a recurring pattern.
Sundowning as Part of a Larger Picture
Veterinarians evaluate cognitive decline using a checklist sometimes abbreviated as DISHAA. Each letter represents a category of symptoms: disorientation, altered social interactions, sleep-wake cycle disruption, loss of housetraining, changes in activity level, and increased anxiety. Sundowning falls under the sleep-wake category, but most dogs showing sundowning behavior also have symptoms in other categories.
You might notice your dog forgetting commands they’ve known for years, having accidents indoors despite a lifetime of reliable housetraining, or losing interest in greeting family members. Some dogs become unusually clingy while others withdraw. Activity changes can go either direction: some dogs become restless and pace during the day too, while others become unusually passive and stare into space. If you’re seeing nighttime agitation alongside any of these daytime changes, CDS is the likely explanation.
There’s no single blood test or scan that confirms the diagnosis. Your vet will rule out other causes of nighttime restlessness (pain, urinary infections, vision loss, hormonal disorders) and rely on your description of the behavioral changes to make the call.
The Only FDA-Labeled Medication
Selegiline is the only drug specifically labeled for canine cognitive dysfunction. It works by protecting certain brain chemicals from being broken down too quickly, which helps maintain whatever signaling capacity the brain still has. It’s effective in up to 70% of dogs with cognitive dysfunction, though “effective” means improvement in symptoms, not a cure. The typical approach is a 30-day trial at a starting dose, with an adjustment upward if the initial response is underwhelming.
One important safety note: selegiline can cause dangerous interactions if combined with certain other medications, including some antidepressants. If your dog takes any other prescriptions, your vet needs the full list before starting treatment.
Beyond selegiline, vets sometimes use melatonin to help reset the sleep-wake cycle. Melatonin has a calming effect and can help dogs rest more comfortably at night, though published research on its use specifically for canine sundowning is still limited. Dosing depends on the dog’s size and the severity of symptoms.
Dietary Support for Brain Health
The aging canine brain becomes less efficient at using glucose, its primary fuel. Medium-chain triglyceride (MCT) oil offers an alternative energy source. MCTs are converted into ketones, which the brain can use even when its glucose metabolism is impaired. In a controlled six-month trial, dogs supplemented with MCT oil at about 9% of their caloric intake showed measurable improvement in spatial memory, problem-solving, and trainability scores.
Several prescription and over-the-counter senior dog diets now include MCTs, antioxidants, and omega fatty acids designed to support cognitive function. These diets won’t reverse brain damage, but they may slow the pace of decline, particularly when started early. Antioxidants help counteract the oxidative stress that accelerates neuron loss in aging brains. Combining dietary changes with medication and environmental adjustments tends to produce better results than any single approach alone.
Managing Sundowning at Home
Environmental changes can make a real difference in how severe and frequent sundowning episodes become. The goal is to support your dog’s failing internal clock and reduce the confusion that triggers anxiety after dark.
Light is one of the most powerful tools. Full-spectrum or warm lighting that mimics natural sunlight can help regulate circadian rhythms. Keeping the house well-lit during the day and using soft, ambient night lights in hallways and your dog’s sleeping area reduces the disorientation that comes with sudden darkness. Some owners find that a consistent “wind-down” routine, dimming lights gradually in the evening rather than switching them off abruptly, eases the transition.
Daytime activity matters too. A dog who sleeps all day is more likely to be restless at night. Gentle walks, puzzle feeders, and short play sessions during daylight hours help burn energy and reinforce the idea that daytime is for being awake. Keep these activities appropriate to your dog’s physical abilities. The point is mild stimulation, not exhaustion.
At night, minimize surprises. Keep furniture in the same place so your dog doesn’t bump into unfamiliar obstacles. Block off stairways or tight spaces where a disoriented dog could get stuck or injured. White noise or calming music designed for pets can mask the sudden sounds (a car door, a neighbor’s dog) that startle a confused dog into a barking episode. Pheromone diffusers, which release synthetic versions of the calming chemical nursing dogs produce, help some dogs settle more easily.
Consistency is the thread running through all of this. Feed at the same times. Walk at the same times. Sleep in the same spot. A dog whose cognitive map of the world is deteriorating relies heavily on routine to feel safe. The more predictable the environment, the less their damaged brain has to work to make sense of it.
What to Expect Over Time
CDS is progressive. The brain changes driving sundowning will continue, and symptoms generally worsen over months to years. That said, the rate of decline varies enormously between individual dogs, and intervention makes a meaningful difference. Dogs started on a combination of medication, dietary support, and environmental management often stabilize for months or even improve noticeably before the condition advances again.
Tracking symptoms week to week helps you and your vet make better decisions. Note when episodes happen, how long they last, and what seems to make them better or worse. Patterns that emerge from a simple log are often more useful than a single vet visit snapshot. Adjustments to medication, lighting, or routine can be fine-tuned based on what the log reveals, keeping your dog as comfortable as possible through each stage.