Sundowning in dogs is a pattern of increased confusion, restlessness, and anxiety that emerges in the late afternoon or evening, closely tied to canine cognitive dysfunction (CCD), a neurodegenerative condition that shares striking similarities with Alzheimer’s disease in humans. Just as people with dementia often become more agitated as daylight fades, older dogs with cognitive decline can show a predictable worsening of symptoms around dusk. The phenomenon is rooted in disrupted circadian rhythms and progressive brain changes, and while it cannot be reversed, a combination of veterinary treatment, dietary adjustments, and environmental management can meaningfully ease the burden on both the dog and the household.
What Sundowning Looks Like in Dogs
Sundowning is not a separate diagnosis from canine cognitive dysfunction but rather a timing pattern within it. Dogs experiencing sundowning tend to be relatively calm during the daytime, then begin showing distress as the light changes in the evening. The most common signs include aimless pacing or wandering, especially along walls or in circles; staring blankly at walls or into corners; vocalizing (whining, barking, or howling) for no apparent reason; seeming lost or disoriented in familiar rooms; increased clinginess or, conversely, withdrawing from family members; and difficulty settling down to sleep. Some dogs stand at doors as if they need to go outside, then appear confused once they get there.
These behaviors overlap heavily with the broader signs of CCD, which include disorientation, changes in social interaction, disrupted sleep-wake cycles, house soiling, and reduced interest in play or learning. Sleep-wake cycle disturbances and aimless wandering are among the hallmark features, and researchers have linked them to amyloid-beta deposits in the cortex and hippocampus, the same brain regions affected in Alzheimer’s disease.1Journal of Veterinary Internal Medicine. An Observational Study with Long-Term Follow-Up of Canine Cognitive Dysfunction: Clinical Characteristics, Survival, and Risk Factors What distinguishes sundowning from general CCD symptoms is the clock: if your dog’s worst episodes cluster in the hours around sunset and into the night, you are likely seeing the sundowning pattern specifically.
Why It Happens
Two intertwined processes drive sundowning in dogs. The first is the accumulation of amyloid-beta protein in the brain. As dogs age, this protein builds up in plaques throughout the cortex, hippocampus, and around blood vessels, much the way it does in humans with Alzheimer’s.2PubMed. Heterogenous deposition of β-amyloid in the brain of aged dogs Research measuring amyloid-beta 42 levels in companion dog brains has found significant positive correlations between these levels and age across the prefrontal cortex, temporal cortex, and hippocampus, and those levels also correlated with scores on cognitive dysfunction scales.3PubMed Central. Canine Cognitive Dysfunction (CCD) scores correlate with amyloid beta 42 levels in dog brain tissue In plain terms, the more plaque in the brain, the worse the cognitive symptoms tend to be.
The second process is the breakdown of the body’s internal clock. In healthy adult dogs, cortisol (a hormone closely tied to the sleep-wake cycle) follows a predictable daily rhythm, rising and falling at consistent times. Studies of aging dogs have found that this circadian rhythm in cortisol essentially disappears in old animals, with no significant changes detectable across a 24-hour period.4Experimental Gerontology. The effects of aging on the circadian rhythm of serum cortisol in the dog When the brain’s clock stops running properly, the dog loses the hormonal cues that normally distinguish day from night. The transition around sunset, when light levels change rapidly, seems to act as a trigger point for confusion in a brain that can no longer smoothly navigate that shift.
This is why sundowning tends to appear in older dogs and why it worsens over time. The amyloid buildup is progressive, and the circadian disruption deepens alongside it. Dogs are not simply “getting old”; their brains are undergoing a neurodegenerative process that parallels human dementia in both the proteins involved and the behavioral consequences.5PubMed Central. Canine Cognitive Dysfunction and Alzheimer’s Disease – Two Facets of the Same Disease?
Which Dogs Are Most at Risk
CCD is primarily a disease of aging. Most screening tools are designed for dogs aged eight and older, and risk climbs steeply with each additional year. Smaller breeds, which tend to live longer than larger breeds, may accumulate more years of exposure to the neurodegenerative process.6Applied Animal Behaviour Science. Prevalence and risk factors of canine cognitive dysfunction syndrome in South Korea That does not mean large dogs are immune; it means they often succumb to other age-related conditions before CCD becomes obvious. Any senior dog can develop cognitive dysfunction, regardless of breed.
There is no single blood test or brain scan that veterinarians routinely use to diagnose CCD in a clinical setting. Instead, diagnosis relies on behavioral screening questionnaires filled out by owners, combined with a veterinary exam to rule out other conditions that can mimic cognitive decline (pain, vision loss, hearing loss, thyroid disease, urinary tract infections, brain tumors). Several validated questionnaires exist. The Canine Dementia Scale (CADES), for example, scores dogs across four domains: spatial orientation, social interaction, sleep-wake cycles, and house soiling, and classifies them into normal aging, mild, moderate, or severe cognitive impairment. Another tool, the Canine Cognitive Dysfunction Rating scale (CCDR), uses 13 questions focused on both current behaviors and changes over the previous six months.7PubMed Central. Comparing standard screening questionnaires of canine behavior for assessment of cognitive dysfunction If your vet has not brought up cognitive testing for your senior dog, it is worth asking, especially if you are noticing evening-specific behavioral changes.
Ruling Out Other Causes
Before attributing nighttime restlessness to sundowning, you and your vet need to consider other explanations. Pain is a big one. Dogs with arthritis or other chronic pain conditions often become more restless at night because lying in one position for hours aggravates their joints. A dog pacing at 10 p.m. might be hurting, not confused. Vision problems can also worsen in low light, making a dog anxious in the dimmer conditions of evening. Urinary tract infections or kidney disease can cause nighttime urgency that looks like disorientation. Thyroid dysfunction, particularly hypothyroidism, can produce lethargy and behavioral changes that overlap with cognitive decline.
The CADES screening protocol, for instance, was developed from a study in which dogs were given clinical exams including blood analysis, urine analysis, radiography, and ultrasound specifically to exclude underlying conditions that could explain behavioral changes.7PubMed Central. Comparing standard screening questionnaires of canine behavior for assessment of cognitive dysfunction This matters practically: if your dog starts acting confused at night but has not had recent blood work or a thorough exam, it is too early to call it sundowning. The behavioral questionnaires are only meaningful once medical causes have been addressed or ruled out.
Veterinary Treatments
The most studied medication for CCD is selegiline hydrochloride (sold under the brand name Anipryl in the United States). Selegiline works by increasing dopamine levels in the brain, which can help with alertness and cognitive function. In a large open-label study of 641 dogs with signs of CCD, about 77% showed overall improvement after 60 days of daily treatment. Improvement rates ranged from roughly 68% for activity and sleep-wake cycle problems to about 78% for disorientation and reduced interaction with family members. Side effects were relatively mild: diarrhea in about 4% of dogs, loss of appetite in about 4%, and vomiting or excessive salivation in about 3%.8PubMed. A noncomparative open-label study evaluating the effect of selegiline hydrochloride in a clinical setting
Those numbers come from a study without a placebo control group, so the true effect size could be somewhat smaller than it looks, since some dogs might have improved on their own or responded to the extra attention of being in a study. Still, it remains one of the few medications with substantial evidence behind it for CCD, and many veterinarians consider it a first-line option. Improvement was already apparent by day 30 in most dogs that responded, so you typically do not need to wait months to know whether it is helping.
Beyond selegiline, veterinarians sometimes prescribe other medications to address specific symptoms. Anti-anxiety drugs can help dogs whose sundowning involves significant distress. Melatonin is sometimes used to reinforce the sleep-wake cycle, though rigorous evidence for its use in dogs specifically for CCD is limited. Your veterinarian may also trial pain medications if there is any suspicion that discomfort is contributing to nighttime restlessness.
Diet and Supplements
Nutrition has emerged as a meaningful part of managing cognitive decline in dogs, particularly when intervention starts early. Research in aged dogs has shown that diets enriched with antioxidants led to significant improvements in the ability to acquire progressively more difficult learning tasks, while younger dogs on the same diet saw no additional benefit, suggesting the antioxidants were specifically counteracting age-related oxidative damage in the brain.9PubMed. Brain aging in the canine: a diet enriched in antioxidants reduces cognitive dysfunction The key antioxidants studied include vitamins C and E, fruits and vegetables rich in flavonoids, and mitochondrial cofactors like alpha-lipoic acid and L-carnitine.
Various studies have shown that diet and dietary supplementation can positively influence the clinical signs of CCD, especially when started at an early stage of the disease.10PubMed Central. Investigating Owner Use of Dietary Supplements in Dogs with Canine Cognitive Dysfunction Medium-chain triglycerides (MCTs), often derived from coconut oil, have attracted particular attention because they provide the brain with an alternative energy source (ketones) when glucose metabolism becomes impaired. Several commercial senior dog diets now include MCTs for this reason. Omega-3 fatty acids, especially DHA, also have some evidence supporting brain health in aging dogs.
The practical takeaway: switching an older dog to a high-quality senior diet formulated for brain health, or adding a veterinarian-recommended cognitive supplement, is a reasonable and low-risk step. These approaches work best as part of a broader management plan and are more effective before the disease has progressed to a severe stage. They are not a substitute for veterinary assessment or medication when symptoms are pronounced.
Environmental and Behavioral Management
Environmental changes can make a real difference for a sundowning dog, and they cost nothing. The core principle is to reduce confusion and reinforce predictable routines. Here are the strategies that matter most:
- Consistent routine: Feed, walk, and settle for bed at the same times every day. Dogs with cognitive decline lean heavily on habit, and unpredictability makes confusion worse.
- Evening lighting: Keep lights on as the sun goes down so the transition from day to night is less abrupt. A sudden shift to darkness can trigger or intensify sundowning episodes. Night lights in hallways and near the dog’s sleeping area can reduce disorientation during nighttime waking.
- Daytime activity: Gentle physical exercise and brief mental stimulation during the day (puzzle feeders, short training sessions, sniff walks) help promote better nighttime sleep. A dog that naps all day is more likely to be restless at night.
- Safe space: Keep the dog’s sleeping area in a familiar, enclosed space. Moving beds to different rooms or rearranging furniture adds to disorientation. Some dogs do better in a smaller room at night where they cannot wander into unfamiliar territory.
- Calm evenings: Reduce household noise and stimulation in the hours before bedtime. Loud television, visitors, or high-energy play in the evening can heighten anxiety in a dog already struggling with the transition to nighttime.
These environmental adjustments parallel advice given to families caring for humans with Alzheimer’s-related sundowning: structure, predictability, gentle lighting transitions, and reduced stimulation. They will not stop the underlying disease from progressing, but they can significantly reduce the frequency and intensity of distressing episodes.
The Toll on Owners
Living with a sundowning dog is genuinely hard, and the emotional and practical burden on owners deserves acknowledgment. Research has found that owners of dogs with CCD report higher levels of caregiver burden compared to owners of cognitively healthy senior dogs.11PubMed. Owners of dogs with canine cognitive dysfunction report higher levels of caregiver burden About 16% of guardians experience a clinically significant level of burden, and the factors that make it worse include the severity of the dog’s CCD, where the dog sleeps (presumably because nighttime disruptions affect the owner’s own sleep), the owner’s employment situation, and household size.12PubMed. Guardians’ perceptions of caring for a dog with canine cognitive dysfunction
Nighttime is where caregiver burden hits hardest. A dog that paces, whines, or barks through the night disrupts the owner’s sleep, and chronic sleep deprivation affects mood, decision-making, and patience. Owners often describe feeling guilty (for being frustrated with a dog that cannot help it), grief-stricken (watching a beloved companion lose themselves), and isolated (because the problem is hard to explain to people who have not experienced it).
There is some encouraging evidence that participating in structured group activities can help. A study of group training classes for dogs with CCD found that caregiver burden decreased significantly over time in owners who participated, regardless of the specific type of class. Owners reported enhanced confidence and social support as key benefits of participation, even though the classes did not change the dogs’ overall CCD severity scores.13PubMed. Group training classes for dogs with canine cognitive dysfunction: effects on sleep, activity, and caregiver burden The social connection of being around other people navigating the same challenges appears to be therapeutic in itself, much like support groups for caregivers of human dementia patients. If a class like this is available in your area, it is worth considering for your own wellbeing as much as for your dog.
Emerging Blood Tests for Early Detection
One of the frustrations with CCD is that by the time owners notice clear symptoms, the disease has often been progressing for years. Researchers are working on blood-based biomarkers that could detect cognitive decline earlier, potentially allowing treatment to begin before significant damage accumulates.
The most promising candidate so far is neurofilament light chain (NfL), a protein released into the bloodstream when nerve cells are damaged. A systematic review of biomarkers for cognitive dysfunction in aging dogs found that while amyloid-beta 42 results were mixed across studies, NfL was consistently elevated in dogs with mild cognitive impairment, suggesting it may have real diagnostic value for catching the disease early.14Journal of Veterinary Behavior. Current and emerging biomarkers of cognitive dysfunction in aging dogs: A systematic review Separate research using an advanced detection method called immunomagnetic reduction showed that plasma NfL levels in dogs with CCD were significantly higher than in cognitively normal dogs.15PubMed Central. Plasma Neurofilament Light Chains as Blood-Based Biomarkers for Early Diagnosis of Canine Cognitive Dysfunction Syndrome
These tests are not yet available as routine clinical tools at your local vet, but the research is moving quickly. The appeal of a simple blood draw that could flag early cognitive decline is obvious: it would allow dietary interventions, environmental changes, and possibly medication to start years earlier than they currently do. Given that antioxidant diets and supplements appear most effective in the early stages of the disease, a reliable early-detection test could substantially change outcomes for aging dogs. For now, regular behavioral screening by owners and veterinarians remains the best tool for catching CCD before it reaches an advanced stage, which is one more reason to bring up any subtle changes in your senior dog’s evening behavior at the next vet visit.