Actual Death Certificate Entry

While researching the Stearns County, Minnesota death certificates that I needed last weekend, I ran across this actual entry for 1918: "Occupation: Senile, (retired)" while the actual cause of death had another chronic illness listed. This example brings several questions to mind, such as, is she retired from senility because of her death? Was that a type of job at the turn of the last century that I've never heard about before? Or how many years had she been retired from senility before she actually died?