Jasper, the fifteen year old Labrador cross, knew that our consultation was finished. He went to the hinge side of the door (rather than the correct, opening side of the door) and he began to bark loudly. His owner commented on this: "He does that all the time now at home as well; it's as if he's forgotten which way doors open".
Jasper was suffering from Canine Cognitive Disorder; this is the elderly dog equivalent of human dementia, and it's very common in old dogs. Nearly 30% of 11-12 year old dogs show some signs, and this rises to nearly 70% of 15-16 year old dogs.
Cats are also affected by a similar condition, again with almost 30% of cats aged 11-14 years developing at least one behavioural problem caused by this, increasing to over 50% of cats over 15 years of age.
The main issue is gradual cognitive decline reflecting slowly progressive pathology of the brain, linked to old age. Often owners don't notice until the signs are very severe: the changes can be so subtle that nothing seems to change day to day, and it is only when it's pointed out, or when it has become quite advanced, that it becomes obvious.
There are many parallels with the human situation. Alzheimer's Disease, the most common type of dementia in humans, is a massive and growing problem for the human population: if we live to the age of 85, our risk of developing dementia is 50:50.
We still don't know why this disease is becoming so much more common: partly, it's because we are an ageing society, living for longer than ever before, as are our pets. And there are also concerns that aspects of our environment may be adding to the problem, with issues like pollutants, food additives, and other aspects of our contemporary lifestyles that are difficult to pinpoint. It's hard to know what we can do about this, other than to live the healthiest lives we can.
Nutrition, exercise, sleep and stress management are all thought to contribute to the gradual development of dementia, over our whole lifetimes.
What about the causes in pets? What causes dementia in dogs and cats, and is there anything that can be done to prevent it or treat it?
The main problem seems to be the simple fact that living tissues degenerate with advancing age. As animals grow older, the brain gradually shrinks, decreasing in weight and size. The numbers of active nerve cells decrease, while glial cells (the inactive, supportive framework of brain tissue) increase in number.
As well as that, there is an accumulation of beta amyloid in the brain; this is a neurotoxic protein that can form plaques that may interfere with the normal functioning of the brain. Research suggests that the more beta-amyloid accumulation, the greater the cognitive impairment, just as in humans with Alzheimer's.
There are also changes in the blood supply to the brain, with microscopic haemorrhages and infarcts (caused by blood clots), leading to damaged blood flow to parts of the brain, causing more degeneration of nervous tissue. There are also age-related changes in the neurotransmitters present in the brain, so that an old brain does not function in the same way as a young brain. And the overall changed metabolism caused by all of the above in the brain leads to inflammation and the release of cytotoxic free radicals, which cause further damage to the degenerating brain tissue.
There are many parallels with the human disease, and dogs have even been used as scientific models to try to understand more about what's happening in humans, and what can be done to help.
The diagnosis in pets is based on the signs shown by the animal in their daily lives, and ruling out other possible underlying diseases. The signs seen include changed behaviour (like going to the wrong side of the door), restlessness, staring oddly for no reason, pacing around randomly, dullness and lethargy, reduced interest in play or exercise, less interest in engaging with people and other pets, and sleep disturbances (e.g. sleeping more than usual in daytime, or being wide awake in the middle of the night).
Increased vocalisation (dogs barking, and cats yowling, for no particular reason) is also commonly seen. Many of these changes are exacerbated by age-related deafness and dimming vision, which is nearly always present in elderly pets at the same time.
Once other causes of these signs have been ruled out, treatment for dementia can be attempted, but there does not been to be any regime that makes a consistent, significant difference. No therapy can reverse the signs, and treatment is generally supportive, just aiming to slow progression of the disease.
A diet enriched with antioxidants, essential fatty acids and so-called mitochondrial co-factors may help, and commercial diets that are rich in these ingredients are marketed for elderly dogs with cognitive decline. Some neurotransmitter-altering drugs are also used sometimes, with variable impact.
Otherwise, as in humans, efforts are made to improve brain function using social interactions, regular exercise, and engaging pets with new toys and new activities. We can't stop the ravages of old age, but we can make it a bit easier for those who go through it.