Correction Appended

LOS ANGELES, June 6— Nancy Reagan once said, ''My life really began when I met Ronnie,'' and she often played the role of adoring wife and political spouse. But as Ronald Reagan weakened over the years at their Bel-Air home and he saw almost no one except a live-in nurse and his wife, Mrs. Reagan seemed to grow stronger.

On the one hand, Mrs. Reagan was physically drained and sometimes despondent over the fact that, as she told friends, her husband no longer recognized her because of Alzheimer's disease.

On the other hand, Mrs. Reagan, whose early White House years were marked by her interests in designer clothes and social events, turned into nothing less than an advocate for Alzheimer's causes and stem-cell research. Supporters say such research could aid the fight against Alzheimer's, diabetes, Parkinson's disease, spinal cord injuries and other serious health problems. The Bush administration has limited how government money can be spent on embryonic stem-cell research because it involves the destruction of human embryos.

Casey Ribicoff, a close friend of Mrs. Reagan's whose husband, the former Senator Abraham A. Ribicoff of Connecticut, died in 1998 after suffering from Alzheimer's disease for many years, said in a telephone interview: ''Even when Nancy went out to lunch or dinner, she was never more than five minutes away. She always had to be very near. It's a long goodbye, a very long goodbye. Nobody knows what it's like. There's no communication. Silence. It's devastating.''

Mrs. Ribicoff said that Mrs. Reagan's involvement with stem-cell research led to meetings with doctors and researchers, motivating the former first lady to call Republican leaders and others in Washington over the last two years to press the case for research behind the scenes. ''She made calls without hesitation,'' Mrs. Ribicoff said. ''She would ask, 'Why are you not supporting this?' ''

Betsy Bloomingdale, one of Mrs. Reagan's closest friends, said Sunday that the stem-cell issue had in essence given Mrs. Reagan, 81, a meaning to her life. Beyond this, Mrs. Bloomingdale said, Mrs. Reagan and her daughter, Patti Davis, reconciled after a strained relationship. ''The wonderful thing that has come into her life is stem cell,'' Mrs. Bloomingdale said. ''Her life has been that, and she's had the children around, which is a wonderful thing, because Patti is in the fold. That's been very special for her, and that's been helpful.''

Though Mrs. Reagan never publicly criticized President Bush on the issue, several friends of hers said Sunday that Mrs. Reagan had been especially disappointed that Mr. Bush, and the Senate majority leader, Bill Frist, were not as supportive on stem-cell research as she had hoped. ''It angered her,'' Mrs. Ribicoff said. ''And I think when Nancy gets her body and heart back together, she's going to work feverishly for stem-cell research and the Ronald Reagan library.''

On Sunday, Betty Adams, a Los Angeles friend of Mrs. Reagan's for nearly 50 years, said of the stem-cell work: ''She's going to work for that very hard from now on.''

Mrs. Reagan grew interested in the issue through Douglas Wick, a film producer who was named a pallbearer for the funeral and whose father, Charles Z. Wick, ran the United States Information Agency under Mr. Reagan. One of the producer's daughters, Tessa Wick, became ill with diabetes in 1999 at the age of 8. Mrs. Reagan soon became engaged in the stem-cell issue after talking to Mr. Wick and his wife, Lucy Fisher, also a producer.

Three years ago, Mrs. Reagan quietly wrote to Mr. Bush saying that she hoped to spare other families what hers had suffered and that stem-cell research could be part of her husband's legacy. Since then, Mrs. Reagan has operated discreetly, making phone calls, sending letters and trying to avoid colliding with the Bush White House.

But early last month, in an unusual public appearance, Mrs. Reagan told a dinner sponsored by the Juvenile Diabetes Research Foundation: ''Ronnie's long journey has finally taken him to a distant place where I can no longer reach him. Because of this, I'm determined to do whatever I can to save other families from this pain. I just don't see how we can turn our backs on this.''

Mr. Wick said that Mrs. Reagan's support on the issue had been ''incalculable, certainly profound.''

He said, ''To some degree, it has really changed the debate.''

Joanne Drake, a Reagan family spokeswoman, was asked by a reporter if there was a sense of relief as well as sadness on the part of Mrs. Reagan at the death of her husband. Ms. Drake said: ''Most certainly. While it is an extremely sad time for Mrs. Reagan, there is definitely a sense of relief that he is no longer suffering and that he has gone to a better place.''

Ms. Drake said that Mrs. Reagan was spending the day resting at her home in advance of the next six days, which will take her from the Reagan library in Simi Valley to Washington and back to Simi Valley for the burial of the former president on Friday.

By all accounts, Mrs. Reagan's life changed irrevocably even before her husband made the public announcement, on Nov. 5, 1994, that he had been told he had Alzheimer's disease, a neurological illness that is characterized by disorientation, a loss of memory and irrecoverable detachment from reality.

Mrs. Reagan's busy social life stopped. She went out infrequently, usually to lunch with friends or visitors from New York at the nearby Hotel Bel-Air.

She rarely discussed her husband's condition and preferred, instead, to distract herself by listening to the latest gossip or discussing the O.J. Simpson trial, which she avidly watched on television.

Michael K. Deaver, Ronald Reagan's image czar, is a longtime friend of Mrs. Reagan and the author of ''Nancy: A Portrait of My Years with Nancy Reagan.''

Mr. Deaver said: ''As the years progressed, she really didn't go anyplace. She was simply there. She might go to lunch or out for an evening occasionally, but basically she was there with him.''