Former first lady Lady Bird Johnson was in stable condition Friday after suffering a mild stroke and losing her ability to speak, her doctor said.

"We are still not sure how permanent this is or how severe this is," Dr. Rodney Horton said of the stroke, which is at least the second for the 89-year-old Johnson since 1993. "It does appear that she has lost the power of speech."

Johnson was taken to a hospital Thursday afternoon after she awoke from a nap at her home and had trouble speaking and swallowing medication. Her doctor said she appears to have suffered damage to a small area on the left side of her brain.

"At the present time, she is fully understanding of everything that is being said, can nod appropriately, but she is unable to find the word," Horton said.

Luci Baines Johnson said her mother was alert Friday.

"She's seizing every moment of life and squeezing out the joy that is to be had," she said.

The only words Johnson has spoken since arriving at the hospital were "thank you," to a close family friend, her daughter said.

Sandra Morgan, a spokeswoman for Seton Medical Center, said there was no indication when Johnson would be released from the hospital. She said Johnson was scheduled to meet with a speech therapist as doctors try to determine if she suffered permanent speech damage.

She described Johnson as "alert and in good spirits" in the intensive care unit.

Johnson was admitted to the same hospital in 1999 after fainting at her home, and underwent cataract surgery that year. In 1993, she suffered what was described as a minor stroke.

While in the White House, from 1963 to 1969, Lady Bird Johnson served as honorary chairman of the national Head Start program and held a series of luncheons spotlighting women of achievement. But she was best known as the determined environmentalist who wanted roadside billboards and junkyards replaced with trees and wildflowers.

Her husband died in 1973. They had been married for almost 39 years.

Although she has been in failing health in recent years, Johnson makes periodic public appearances at the LBJ Library and Museum and at civic events in Austin.

She also has remained active in her family business, the privately held LBJ Holding Co., but has handed leadership duties of the broadcasting company to her daughter.