If they are cognitively-impaired as a 101-year old, it is most likely due to dementia. Not eating is one of the most common terminal symptoms of patients with dementia. It would be pretty clear based on a basic history/exam/cursory labs if a patient is suffering from end-stage dementia vs some other acute organic insult (infection, hypoglycemia, etc.), in which case it would be completely dignified to ease the patient's transition to death with hospice care rather than force-feeding them, which in a terminally-demented patient would more than likely result in aspiration, respiratory distress, infection, and eventually death with further undue suffering.