Video report by ITV Meridian's Malcolm Shaw
Around 850,000 people in the UK are living with dementia and the condition affects 1 in 6 people over 80.
But research shows that our pets can also develop a condition similar to Alzheimer's in humans, with symptoms including confusion and forgetfulness.
Vets say the majority of cases in pets go undiagnosed, which can deprive the animals of possible help.
The Collins family pet Mia was a much-loved companion throughout her long life, but the family say her behaviour started to change as she got older.
Mia passed away earlier this year from another condition.
Sarah Collins, Mia's owner
Vets believe around 85% of cases of pet dementia currently go undiagnosed, with more than one million elderly dogs and cats across the country suffering in silence.
Dr Julia Mewes, Veterinary surgeon
Now, an online symptom checker has been launched by Vets4Pets, helping owners to spot the signs, and seek advice if the score indicates there could be a problem.
Some symptoms of pet dementia include:
Inappropriate vocalisation (howling, barking or whining)
Repetitive behaviour, such as pacing
Staring at walls
Fewer social interactions
There's currently no cure for dementia in dogs and cats, but vets say some medications and changes to diet can help with symptoms.