"He's always been a very calm, gentle person but he started to develop a temper which he had never had before.
"He had sudden spurts of anger that have increased over a period of 10 or so years."
Dementia sufferers' anger often stems from frustration, said Kāpiti dementia adviser Sheena Farquhar.
"When people can't quite say what they want to do, or you are doing things slower because your brain is working slower you get really frustrated. It's been a long process," Katy said.
"He slowly started to not seem like himself."
They eventually started talking to doctors about three years ago and received a diagnosis two years ago after a final brain scan.
"We were reluctant because we knew he would eventually lose his licence.
"While it didn't happen straight away, when it did it hit us badly."
"Since losing my licence it has cut us off," said Andrew. "That has been the biggest hurdle."
There has been history of dementia in Andrew's family - his brother and aunt also have the condition.
However, according to Sheena, dementia was usually not genetic.
Andrew and Katy have been attending Cog Cafe at Lindale, a programme for people with dementia to socialise and connect.
There were five aspects to keeping your brain healthy which are especially relevant to dementia patients, Sheena said. They were keeping healthy, exercising, having a healthy diet, challenging your brain by learning something new and being social.
For Andrew having a new granddaughter has kept him on his toes.
"It really takes him out of himself, it's like learning something new again, we've forgotten what babies are like," Katy said.
"With children they are very accepting as well, they don't see the changes."
Andrew's day-to-day memory has been the first thing to go.
"It sends you crazy having to repeat yourself constantly.
"He never knows whether he's had breakfast or lunch."
But Andrew keeps up with the gardening and will happily help out around the house, and even enjoys doing the vacuuming.
Andrew and Katy say the hardest thing has been less contact with people.
"No contact is the hardest," Andrew said.
"I enjoy social contact so I'm glad that I'm physically healthy as otherwise it would be a lot harder for us."