NRL great Royce Simmons says it’s only a matter of time until dementia completely takes over his life, a reality being faced by almost half a million Australians right now.

Those 433,000 Australians living with dementia are the reason why the Penrith legend will set out on his fourth annual “Big Walk” next month, hoping to raise funds for dementia research programs.

Simmons, accompanied by fellow ex-players including Terry Lamb and Luke Goodwin, will walk from Penrith for 11 days and more than 200km, beginning on August 13.

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He’ll arrive at Glen Willow Oval in Mudgee for Penrith’s Round 25 clash against Canberra - a fitting destination for the hero of the Panthers’ inaugural grand final win over the Raiders in 1991.

But the walk is about much more than footy for Simmons, who was diagnosed with dementia in 2022 at only 61 years of age.

“When I was diagnosed, I sat around whingeing, really frustrated and cranky with the world,” he told AAP.

“After I did that for a few months, I thought, get off your bum and get out and try to do something positive.

“That’s the reason why I’m in it now, trying to help out as much as I can before the dementia gets me any worse.

“I know it’s only a matter of time until I go down that track.”

Even now, as he lies in bed in the morning, it can take Simmons more than half an hour to remember what he did the previous day.

“You wake up in the morning and you think to yourself, ‘What did I do yesterday?’ You lie there for half an hour and you think and you think and gradually you work it out,” he said.

“Then I suppose the stage comes where you don’t.”

Simmons has despaired at seeing his mates go down that path, so he has helped create a “virtual steps” program that allows donors to pay $30 to complete 30 steps “alongside him” this year.

“I’m not just crying out to Penrith fans, I’m crying out to all rugby league fans,” he said.

Simmons is hopeful he’ll arrive in Mudgee for another Penrith win, with the four-time reigning premiers currently on a five-game winning streak that has revived their season.

The 66-year-old said a fifth consecutive premiership shouldn’t be out of the question.

“They gradually just build their way into it every year, pick up some momentum, and things are looking positive again this year, but there’s still a fair way to go,” Simmons said.