Sundowning in Old Dogs: Night-Time Restlessness and What Helps

When an old dog sleeps most of the day and paces, pants or vocalizes through the night, the most common cause is canine cognitive dysfunction, the dog version of dementia. The AAHA 2023 senior care guidelines list daytime sleeping and night-time restlessness among its most common signs, and the people who care for these dogs often call it “sundowning.” The first step is a vet visit to rule out other causes; after that, a day full of activity, a predictable night, and sometimes diet, supplements or medication can make a real difference for the dog and for you.

What “sundowning” means in dogs

It isn’t a formal diagnosis. Cornell’s Riney Canine Health Center mentions owners describing “sun-downer syndrome,” meaning worse symptoms and irritability at night, but most veterinary sources describe it as a change in the sleep-wake cycle, one of the six DISHAA areas vets use for cognitive dysfunction. VCA puts it plainly: dogs sleep more during the day and then become restless, often pacing during the night. In a 2025 survey of US vets, changes in sleep and wake cycles were the most used sign for diagnosing the condition.

It is common. The AAHA guidelines estimate that about 14–22.5% of dogs older than 8 have age-related cognitive impairment, and a study cited by Merck found signs in 28% of dogs aged 11 to 12 and 68% of dogs aged 15 to 16. The free dog dementia signs checklist helps you note the other signs to bring to your vet.

Rule out the other causes first

Cognitive dysfunction is a diagnosis of exclusion (AAHA). Before calling it dementia, your vet will look for other reasons an old dog can’t settle at night:

• Pain, especially arthritis. A 2023 study of 802 senior dogs found a strong link between musculoskeletal and neurological conditions and cognitive scores, and its authors advise screening dogs with cognitive signs for pain.
• Needing to urinate more, from a bladder infection or other illness (Cornell, ASPCA).
• Vision or hearing loss, which can make sleep lighter (ASPCA).
• Other illness, including brain disease; the AAHA guidelines mention imaging when a structural cause is suspected.

Reset the day and night

The Merck Veterinary Manual describes the core of management: more light during the day, a dark room at night, and a consistent place and time for sleeping, inside a predictable daily routine. In practice:

• Fill the day. Walks at your dog’s comfortable pace, sniffing, puzzle feeders and other gentle enrichment; Merck says treatment should focus first on environmental enrichment.
• A short walk before bed. Cornell notes an extra walk right before bedtime can lead to longer, deeper sleep for some dogs.
• Extra potty breaks, including one late in the evening (Cornell, VCA).
• Night-lights so your dog can see and is less likely to get stuck (Cornell).
• A calm room. The AAHA guidelines list temperature control, nightlights, sound machines and access to sunlight among home aids.
• Keep things where they are. Bed, food and water in the same places, clutter cleared, and traction on slippery floors (Cornell, AAHA).

The AAHA guidelines make a point worth remembering: if a dog is pacing and panting all night, easing the sleep problem first can relieve the whole household.

Diet and supplements

Some therapeutic diets, rich in antioxidants and medium-chain triglycerides, have been studied for cognitive dysfunction, and the AAHA guidelines note they worked best combined with environmental enrichment. VCA says any benefit is typically seen within 6 to 12 weeks, and that if nothing improves after 12 weeks, diet alone is unlikely to help.

Melatonin is the supplement people ask about most. Cornell says it helps some dogs but there aren’t many studies to confirm it, and a 2025 review notes it hasn’t been studied specifically in dogs with cognitive dysfunction. The AAHA guidelines add two cautions: some melatonin products contain xylitol, which is toxic to dogs, and melatonin can contribute to serotonin syndrome when combined with certain medications, including selegiline. Ask your vet before giving it.

Medication

Selegiline is the only drug labeled for canine cognitive dysfunction, the AAHA guidelines say, and Cornell notes many owners report it helps with night-time symptoms. It must not be combined with certain antidepressants (Merck). For nights, the AAHA task force prefers short-acting medications such as trazodone where an anxiolytic is needed. All of these are your vet’s decisions, matched to your dog’s other conditions and medications; never give your dog human sleep aids.

Looking after yourself

Broken nights wear down everyone in the house. Keep a simple log of how each night goes, so you and your vet can see whether changes are working, and lean on your vet for a plan rather than waiting it out. The dog dementia signs guide covers the wider picture, and the senior dog wellness tracker helps you keep the dated notes your vet needs.