Your elderly dog's sleep habits have changed so gradually you don't know when it began. Where he used to sleep through the night and be active during the day, you now find that he sleeps most of the day and not only is awake, but agitated for a few hours at night. This behaviour is called sundown, and it is part of a larger medical condition called canine cognitive dysfunction syndrome (CDS), or age-related dementia.
Canine Cognitive Dysfunction Syndrome
Canine Cognitive Dysfunction Syndrome (CDS) is a medical condition often compared to human Alzheimer's disease. It involves the breakdown of brain tissue. The disease is progressive and irreversible, and can happen to any dog in the last third of her lifespan, typically over age 8. Sundowning is one symptom of CDS.
Symptoms of sundown include decreased activity during the day followed by increased, purposeless activity at night. Your dog may pace or wander around the house, or may bark at night for no reason.
Symptoms of CDS, in addition to sundown, may also include other behavioural changes. Your dog may get stuck in corners or behind furniture. He may need to be led back into the house after going outside. He may stare into space or seem confused. He may not greet family members or seem to recognise familiar people. He may walk away while being petted. He may begin to eliminate waste inside the house, even having just come in from outside.
Diagnosis and Treatment
Your veterinarian will take a full history of your dog's general health and recent changes. She may perform blood and urine tests to check for metabolic disorders, kidney and liver disease. Decreased acuity of the senses may also account for behavioural changes. After ruling out all these possibilities, your veterinarian may diagnose CDS. She may prescribe a once-a-day pill called Anipryl, which does not reverse CDS, but does alleviate the symptoms.