[2] On May 13, 2015, her husband Keisuke Sagawa revealed on a radio show that she was living with dementia, putting any planned future work on indefinite hold.

[7] While her dementia had progressed, it was last said in October 2017 that she was in good health despite her condition, and enjoyed interacting with the other residents and partook in activities such as choir.

[9][10] It was revealed in articles covering her death that over the past year, she started suffering from health problems and had difficulty speaking due to senility.

[10][15] At her funeral, it was said that there was a photograph of her late husband Sagawa, a chestnut yokan from Toraya, and a stuffed toy of Doraemon by her side inside the coffin she was in.

[17] The voice actress for Doraemon since 2005 in the current series, Wasabi Mizuta, expressed her remembrance over Ōyama on her official blog on October 12 in honor of her death.