The Playboy founder insisted that he is "consistent" in his relationships because he has been dating 20-year-olds for 65 years.
He told Metro: "If you're in good health, age is just a number. I'm consistent; when I was 20 I was dating 20-year-old girls and now I'm 85 I'm still dating them.
"We have lots in common. A very similar sense of humour. I can't foresee having a happier relationship than this one in the years ahead for me."
Hefner also explained that he has fought racism, sexism and is now battling ageism.
He told Time: "To begin with I fought racism, then sexism, now I'm fighting ageism. One defines oneself in one's own terms. If you let society and your peers define who you are, you're the less for it."
Hefner has claimed that the women's movement in America has a puritanical element to it.