Michael J Fox has described Parkinson's as a "bully".

The 64-year-old actor - who was diagnosed with the neurodegenerative disease in 1991 - has reflected on the enduring popularity of Back To The Future, and how the modern world's "bully culture" means the time travel saga still resonates with people.

He told Empire magazine: "We live in a bully culture right now. We have bullies everywhere -- you don't need me to point the finger at who, but there are all these bullies.

"In this movie, Biff is a bully. Time is a bully. For me personally, Parkinson's is a bully.

"And it's all about how you stand up to them and the resolve that you take into the fight with them. It's about your resilience and your courage."

He pointed to the way the film has a David and Goliath story, which is something film fans can still take something from.

He added: "I think there's a lot to that right now.

"I think a lot of people are responding to the movie because it strikes chords they wouldn't otherwise recognise."

Michael previously explained how he tries to keep his sense of humour "intact" amid his battle with Parkinson's, which causes uncontrollable movements, such as shaking, stiffness, and difficulty with balance and coordination.

He told People magazine: "It's hard for me. But I gotta keep it intact."

In the years since his diagnosis, the Back to the Future star has established the Michael J. Fox Foundation - which is dedicated to finding a cure for Parkinson's and has gone on to fund $2 billion worth of research - and upon its annual gala, stars such as Stevie Nicks arrived to show their support.

He said: "I can't believe -- a lot of these people I've known for years and years -- they're so kind to me.

"I think because they see an opportunity for a win, for a big advancement, and that's what we're working toward."