Tom Magliozzi, one of the hosts of the National Public Radio show "Car Talk," died yesterday (Nov. 3) from complications of Alzheimer's disease, according to news reports. But how does Alzheimer's disease kill?

Alzheimer's is perhaps best known for its effects on memory, but the condition is a progressive brain disease in which abnormal protein deposits build up in the brain, which causes brain cells to die.

But 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, said Dr. Marc L. Gordon, chief of neurology at Zucker Hillside Hospital in Queens, New York, who was not involved in Magliozzi's care.

Most often, the complications of the debilitating disease are what cause the death of Alzheimer's patients, Gordon said. [Alzheimer's vs. Normal Aging: How to Tell the Difference]

These complications include infections, such as infections of bedsores that occur when people stay in bed for prolonged periods. Alzheimer's patients also may have difficulty swallowing, and they may inhale food, which can result in aspiration pneumonia, Gordon said. Pneumonia is listed as the cause of death in as many as two-thirds of patients with dementia, according to the Alzheimer's Society, a charity in the United Kingdom for people with dementia.

Alzheimer's patients also can develop fatal blood clots — another complication of being bedridden, Gordon said.

Alzheimer's disease is the sixth-leading cause of death in the United States, according to the Centers for Disease Control and Prevention. In 2010, nearly 85,000 people in the United States died from the disease, the CDC says.

But a study published in March of this year suggested that the number of deaths from Alzheimer's disease may be five to six times higher than what the CDC reports. That's because the people filling out death certificates may not list Alzheimer's disease as an underlying cause of death, either because there are other underlying causes (such as infection), or because the person does not know that the patient had Alzheimer's disease.

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