Betty White died from a stroke ... a stroke she suffered nearly a week before she passed ... TMZ has learned.
Betty's cause of death is listed as a cerebrovascular accident, according to her death certificate, which is a loss of blood flow to part of the brain, resulting in brain tissue damage.
It's interesting ... the certificate, obtained by TMZ, says Betty suffered the stroke 6 days before her death.
Sources with direct knowledge tell TMZ ... Betty was alert and coherent after the stroke, and she died peacefully in her sleep at home.
A cerebrovascular accident can be caused by blood clots or broken blood vessels in the brain.
TMZ broke the story ... Betty passed away at her home on the final morning of 2021 ... less than 3 weeks before she would have celebrated her 100th birthday.
Betty's birthday -- January 17 -- will still see the debut of a movie honoring the milestone, "Betty White: 100 Years Young -- A Birthday Celebration" ... and it features tons of stars, including Ryan Reynolds, Tina Fey, Robert Redford, Lin Manuel-Miranda, Clint Eastwood, Morgan Freeman, Jay Leno, Carol Burnett, Craig Ferguson, Jimmy Kimmel, Valerie Bertinelli, James Corden, Wendy Malick and Jennifer Love Hewitt.
Meanwhile, in her Illinois hometown, Jan. 17 will be a celebration dubbed "Betty White Day."
As we first told you ... Betty rarely left her home during the pandemic, passing the time by doing crossword puzzles, watching TV and reading.