Wednesday, March 11, 2015

Aging vs illness: what are the signs of cognitive dysfunction in dogs and cats?

older pets, cognitive dysfunction syndrome, senior pet, senior dog, senior cat
Older pets may change their behaviour. This is the late Little Man.What a beautiful soul he was.

Have you ever lived with a senior dog or cat? Ever noticed behavioural changes that you attributed to just “getting old”? How can you differentiate signs of aging from other ailments in companion animals?

I grew up with a tough old cat who had survived a number of motor vehicle accidents. As she got older, she started acting weirder. She would strike those who dared to pat her, lose control of her bladder inside and howl at the bathroom cupboard at 3am. In hindsight, in her latter years I believe she was suffering from a combination of medical conditions as well as behaviour changes caused by cognitive dysfunction syndrome.

I recently learned that the term “inflamm-aging” (a progressive increase in the body’s inflammatory response as we age) is believed to be responsible, at least in part, for cognitive dysfunction syndrome (CDS). (I do love it when scientists invent words. It also sounds like a good excuse for a day off, "sorry, I can't come to work today, I'm inflammaging").

Signs of CDS include (but aren't limited to):
  • Inappropriate toileting (e.g. a house-trained dog might go on a walk, then come back inside, then in front of everyone just go to the toilet in the house).
  • Disorientation/confusion (e.g. starring at the walls for no reason, getting stuck behind furniture).
  • Excess vocalisation
  • Changes in activity levels – for example, increased restlessless
  • Changes in amount of interaction with humans
  • Apparent failure to recognise familiar humans
  • Increased anxiety

But before we blame aging, other conditions can cause these signs. Diseases such as chronic renal disease, osteoarthritis, urethral sphincter mechanism incontinence, cardiovascular disease, immune mediated disease and cancer can cause the same signs. Age related vision and hearing impairment can lead to behaviour changes that are similar to CDS, and often occur concurrently with CDS.

It is estimated that around 22 per cent of dogs 9-17 years old, and 50 per cent of cats over 15 will have behavioural changes consistent with CDS. But many of those patients will have concurrent physical ailments. This can make diagnosis a bit tricky. Furthermore, not all owners tell their vet. While 75 per cent of owners felt their dog had at least one sign of CDS, only 12 per cent told their vet.

There is no definitive diagnosis for CDS, rather it is based on consistent behavioural signs and ruling out underlying disease. A full physical examination, complete blood count, biochemistry panel, urinalysis, thyroid testing and potentially imaging should be carried out to rule out underlying disease. In cats fed a diet high in sulphur dioxide preservatives (usually if pet mince is fed), either the cat’s thiamine levels or the levels of sulphur dioxide in the food can be tested.

A very important part of this investigation should be a comprehensive history. What do these animals do during the day and night? Has this been a gradual or sudden change? Do the animals seem worse in some situations, e.g. when the lights are off? Videos of the behaviour (such as those taken on smart phones and tablets) can be really helpful.

CDS and human dementia both result in changes to the brain, although we don’t routinely image or biopsy the brain. According to animal behaviour specialist and veterinarian Kersti Seksel, changes associated with CDS include but are not limited to:

  • Reduced frontal volume
  • Increased ventricular volume
  • Calcification of the meninges
  • Demyelination
  • Increased lipofuscin and apoptotic bodies
  • Neuroaxonal degeneration
  • Reduction in the total number of neurons

In cats, changes include:
  • Vascular insufficiency and subsequent hypoxia
  • Increased free radical damage
  • Deposition of beta amyloid plaques (although the association of amyloid deposition and signs of CDS in cats is not consistent).

For dogs, a validated questionnaire is available online here.

There is unfortunately no cure for CDS, however a few things might help.
  1. Treating or managing concurrent medical conditions can make a huge difference, for example diabetes or chronic kidney disease.
  2. Medication can help. Propentofylline is used in some human patients with Alzheimer’s and may benefit by increasing cerebral blood flow and inhibiting platelet aggregation and thrombus formation. Selegiline is an antidepressant drug (a monoamine oxidase inhibitor) that might also be helpful.
  3. Diets containing anti-inflammatory nutrients such as antioxidants and fatty acids may be helpful. There is a commercial diet for dogs but none for cats.
  4. Just like keeping our brains active is meant to keep some of the effects of aging at bay in people, ensuring pets are simulated may help. Environmental enrichment and structured activities can help.
  5. Avoid sudden changes (e.g. completely rearranging the furniture) and keep a structured daily routine where possible. In some cases I advise clients to block off stairs with a toddler gait or at least remove access as some animals do become disoriented and, like older people, are at increased risk of falls.

Simple changes can be enough to improve a senior pet's quality of life. Regular veterinary checkups are important in ensuring that all diseases are managed appropriately.

Don't forget to enter SAT's David Attenborough Giveaway. Its very easy, see here for details.


Salvin HE, McGreevy PD, Sachdev PS et al (2011) The canine cognitive dysfunction rating scale (CCDR): a data-driven and ecologically relevant assessment tool. Veterinary Journal 188:331-336.

Seksel K (2012) Senior care: Behavioural Disorders. Elsevier Australia Medical Communications for MSD Animal Health.