In late stage Alzheimer's disease, people become extremely confused and disoriented. Eventually they lose the ability to communicate, and may not respond at all. They are unable to care for themselves, becoming bedbound and completely dependent on others. Their appetite declines, and eventually they lose the ability to swallow, leading to high risk of aspiration. This explains why more than 90% of the more than 5 million people with dementia in the U.S. are in a nursing home when they die.
Under these difficult conditions, it's not hard to imagine how vulnerable people with late-stage dementia become to succumbing to infections, pressure sores and pneumonia. One study found that half of all people with dementia admitted to a hospital for pneumonia or a hip fracture died within six months of leaving the hospital.
Javier, Noel S.C., MD, "Palliative Care for the Nursing Home Resident with Dementia", Medicine and Health Rhode Island 93; 12:379-81, December 2010.