Alzheimer's disease, which is a progressive degeneration of the brain, affects millions of lives worldwide. However, there was no awareness about the condition until very recently.

Some credit for spreading awareness about Alzheimer's disease goes to Seth Rogen, who started holding an annual event -- Hilarity for Charity -- where all his comedian friends perform to raise money for Alzheimer's research. His mother-in-law battled Alzheimer's for a long period and he wrote about it in an essay for Glamour magazine:

"It was a long process, but slowly, over years, caring for Adele became a 24/7 job for Lauren's father. At first she was fine at home alone; eventually she needed a wheelchair and someone to feed her and clean her. Lauren and I started to realize that caring for Adele occupied 100 percent of her father's life. We needed to try to help him. That's when we moved her parents to L.A., just a few blocks from where we live."

This year, the star of Rogen's upcoming movie "Neighbors 2: Sorority Rising" is also helping him out.

In commemoration of World Alzheimer's Day, we have compiled a list of famous celebrities, who battled the disease:

  •  William Asher: A prolific television director, best known for his work on "I Love Lucy" and "Bewitched".
  • Glenn Campbell: The country singer and guitarist, who made history by winning four Grammys in 1967.
  • Dana Andrews: Movie star best known for his Oscar-winning "The Best Years of Our Lives".
  • Ronald Reagan: The 40th President of the United States (1981 to 1989).
  • Mabel Albertson: Actress best known as Darrin's neurotic, interfering mother on the sitcom "Bewitched".
  • Arlene Francis: Radio talk show host and game show panelist who was part of the television game show, "What's My Line?"