The film, made by Media Trust's production team, tells the stories of three older people who are defying the stereotypes often associated with their age.
Ena Mallet (79) is a 7th Dan jujitsu practitioner who teaches martial arts classes.
'Mamy Rock' (72) is a nightclub DJ who has toured all over the world since taking up DJ-ing at the age of 68.
And 72-year-old Geoffrey Palmer is a world-renowned grain scientist and university lecturer who proclaims there is no reason why an older person cannot still innovate.
The Age Old Excuse film finishes with Star Trek star Stewart who is aged 72 himself, stating that "age is just a number".
The film's director, Gavin Toomey, said: "I worked closely with Macmillan on this film and wanted it to be something they could use to really bring to life their Age Old Excuse campaign."
The film will be used by Macmillan to campaign to improve the care and treatment of older people. The charity is calling for older people to be offered treatment based on their fitness not their age.