With the very recent passing of Tom Magliozzi on November 3rd, one of the hosts of NPR's "Car Talk", due to complications of Alzheimer's, recent reports are quick to try and explain just how Alzheimer's disease causes death.
Alzheimer's is a progressive brain disease in which deposits of abnormal proteins build up on the brain and cause brain cells to die. However, Dr. Marc L. Gordon, chief of neurology at Zucker Hillside Hospital in Queens, New York, says that "Alzheimer's disease is not usually a direct cause of brain death — that is, it does not suddenly cause the entire brain to cease functioning. Most often, the complications of the debilitating disease are what cause the death of Alzheimer's patients." (source)
These complications include infections, bedsores, and aspiration pneumonia, which occurs when Alzheimer's patients (who often have difficulty swallowing) inhale food. Pneumonia is responsible for nearly two thirds of the deaths of patients with dementia, according to the Alzheimer's Society.
Though the CDC reported in 2010 that approximately 85,000 people in U.S. died from Alzheimer's disease, a recent study shows those numbers may be up to six times higher, due to many death certificates not listing Alzheimer's as an underlying cause of death.