Betty White's cause of death has been revealed.
The Golden Girls star, who passed away on Dec. 31 at age 99, died due to a cerebrovascular accident, according to her death certificate obtained by PEOPLE on Monday. TMZ was the first to report the news.
A cerebrovascular accident, commonly known as a stroke, is a loss of blood flow to part of the brain, which damages brain tissue. It is typically caused by blood clots and broken blood vessels in the brain.
According to the death certificate, White suffered a stroke six days before her death.
A source tells PEOPLE "It was a mild stroke. She died peacefully in her sleep."
White's longtime agent and friend Jeff Witjas also tells PEOPLE: "Betty passed in her sleep peacefully without pain. To me this is the most important thing and brings me comfort as her dear friend. Anything else is private to Betty."
getty Betty White
White's agent and close friend Jeff Witjas first confirmed to PEOPLE in a statement on Dec. 31 that the beloved actress "died peacefully in her sleep at her home" that morning.
"Even though Betty was about to be 100, I thought she would live forever," Witjas said. "I will miss her terribly and so will the animal world that she loved so much. I don't think Betty ever feared passing because she always wanted to be with her most beloved husband Allen Ludden. She believed she would be with him again."
"People are saying her death was related to getting a booster shot three days earlier but that is not true," Witjas said in a statement to PEOPLE on Jan. 3. "She died of natural causes. Her death should not be politicized — that is not the life she lived."
Vivien Killilea/Getty Betty White and Jeff Witjas
White, who was preparing to celebrate her 100th birthday on Jan. 17, recently opened up to PEOPLE about her feelings about the milestone occasion.
"I'm so lucky to be in such good health and feel so good at this age," she said at the time. "It's amazing."
In 2012, White said she had "no fear or dread of death" in a TimesTalks conversation with New York Times columnist Frank Bruni. She credited her mother's approach for impacting her view of the subject, adding that she was "happy as a lark to stay around as long as I can."
"My mother had a wonderful approach to death," White told Bruni. "She always thought of it as — she said, 'We know we have managed to find out almost anything that exists, but nobody knows ... what happens at that moment when it's over.' "
"And she said, 'It's the one secret that we don't know.' So whenever we would lose somebody very close and very dear, she would always say, 'Well, now he knows the secret.' And it took the curse off of it somehow."
getty Betty White
On Friday, Witjas told PEOPLE that she knew of the love fans had for her during her finals days, adding that he would remind her of it "often."
"Even when she wasn't working, I said, 'Betty, millions of people out there are still asking for you. You're getting your fan letters, I'm getting offers for you,'" he said. "I don't know if she ever embraced it, [or] really, really felt it. The extent of it. I really don't. I would always reinforce it with her because I always felt she should know that. I never wanted her to think while she was sitting at home, that the world has passed her by. It never did."
"Betty lived a great life and she lived a life that she chose," he added. "She was happy. Every time I told her, 'Betty, you're loved,' she would look at me with a wry smile and say, 'Really?' I hope she knew. I think she did. It was something beyond love."