Former President Ronald Reagan turns 90 Tuesday, as he battles Alzheimer's disease and recovers from a broken hip he suffered in a fall last month. The celebration will be a subdued one, spent with his wife of nearly 49 years, Nancy, at his home in Bel Air, Calif., where he recovering from his Jan. 12 fall. "We will celebrate Ronnie's 90th birthday very quietly here at home with a birthday cake (likely his favorite chocolate), of course!" Mrs. Reagan told The Associated Press. "He looks fine. I mean, you know, his skin, and he's got a full head of hair . . . I mean, when the barber comes to cut his hair, he has to thin it!" Mrs. Reagan said on a "Larry King Live" show scheduled for broadcast Tuesday. She added that Reagan seems to be on the road to recovery. "Right now he is involved in simple physical therapy that has him sitting up twice a day in a special orthopedic chair that helps to keep his leg straight," Mrs. Reagan said. "He has been sitting in it longer each day and the doctors and physical therapists are encouraged that this is giving him the strength to begin with weight-bearing therapy in the next seven to 10 days." Reagan learned that he had Alzheimer's in 1994, when he withdrew from public view with a poignant letter about his diagnosis. . "I only wish there was some way I could spare Nancy from this painful experience," he wrote. Since then, Mrs. Reagan has vigilantly guarded his privacy. One close friend, Merv Griffin, fondly remembers past Reagan birthdays. "Ronnie's birthday was always the fun event of the year . . . sometimes at the ranch with cowboy clothes and the horses milling around, sometimes at Chasen's (restaurant) with the Washington leadership," Griffin said. "But always his acknowledgment of his birthday was the same. This year it would have been, 'Thank you for acknowledging the 51st anniversary of my 39th birthday.' "Reagan is one of only three presidents to reach 90. John Adams and Herbert Hoover are the others.