How Does Alzheimer’s Kill?

Today’s New York Times obituary for elections analyst Richard Scammon listed his cause of death as Alzheimer’s disease. How does this illness cause death?

Death by Alzheimer’s disease, a progressive brain disorder characterized by loss of memory, is usually caused by secondary infections that are common in incapacitated patients. There are about 4 million Americans with the disease, and the average length of time between diagnosis and death is eight years, although people can live with the illness 20 years or more. As the disease progresses, patients lose the ability to coordinate basic motor skills such as swallowing, walking, or controlling bladder and bowel. Difficulty swallowing can cause food to be inhaled, which can result in pneumonia. Inability to walk can lead to bedsores. Incontinence can result in bladder infections. These infections become particularly difficult to deal with because Alzheimer’s patients are unable to understand and participate in their own treatment. While reports say that former President Ronald Reagan, an Alzheimer’s sufferer, is recovering well from his broken hip, such falls often lead to death because the patient does not have the capacity to follow directions or motivation to try to walk again. Such incapacitation again sets the stage for deadly infections. Doctors say it is possible that an Alzheimer’s patient could progress to the point that damage from the disease to the centers of the brain that control breathing could cause death, but patients rarely get that far without an infection setting in. Once a patient is extremely incapacitated, there is little medical motivation to aggressively treat such infections.

In 1998, Alzheimer’s disease was the 12th-leading cause of death in the United States, with 22,725 deaths, and the ninth-leading cause for people 65 and over. That number is expected to increase when statistics for 1999 are released. That’s because a new reporting system will reflect a change that lists Alzheimer’s as the primary cause of death even if the patient died of Alzheimer’s-related pneumonia. Experts say Alzheimer’s deaths have been underreported because infections such as pneumonia were listed on death certificates instead of Alzheimer’s. According to the Boston Globe, Massachusetts, which has released its 1999 numbers, has seen a 50 percent increase in reported Alzheimer’s deaths under the new system and about a 25 percent drop in reported deaths due to pneumonia.

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Explainer thanks Dr. Peter J. Whitehouse of the Case Western Reserve University School of Medicine, Dr. Harry Rosenberg of the National Center for Health Statistics, and Danny Chun of the Alzheimer’s Association.