How Does Alzheimer Disease Eventually Kill You?

According to 2105 data from the Centers for Disease Control and Prevention, Alzheimer disease (AD) is the sixth most common cause of death in the United States. AD describes a progressive degeneration of the gray matter of the brain, which controls thinking, memory, movement and sensation. The white matter of the brain -- the part responsible for communicating among regions of the brain -- is also damaged in AD. AD-related brain changes affect memory centers first but advance to other functional regions of the brain. While people with AD may die of other unrelated conditions, such as a heart attack, death from AD typically results from complications related to loss of critical brain functions.

How Does Alzheimer Disease Eventually Kill You? Credit: kzenon/iStock/Getty Images

Pneumonia and Other Infections

Pneumonia is leading cause of death in people with advanced AD. As the disease progresses, the abilities to walk, sit upright and swallow normally decrease. Lack of mobility diminishes the capacity of the lungs to expand and manage normal secretions properly, increasing susceptibility to pneumonia. Additionally, poorly coordinated swallowing can allow food, liquid and saliva to enter the airways, causing a particularly aggressive form of pneumonia. Pneumonia may be the final complication, but AD is the cause of death in these situations.

Other infections also frequently occur in people with advanced AD, which can ultimately lead to death. Common examples include urinary tract infections and serious skin infections, often due to ulcers or bed sores.

Dehydration and Malnutrition

Difficulty swallowing, loss of interest in eating, diminished capacity for self-feeding and inability to express hunger or thirst -- all of which occur frequently with advanced AD -- may decrease intake below the level necessary for normal organ function. Many serious and ultimately fatal problems can result from dehydration and malnutrition, including kidney failure, coma, the formation of bed sores, inadequate heart function and reduced resistance to infection.

Automobile Accidents

There are conflicting studies regarding the risk of fatal car accidents among drivers with AD, but the evidence of impaired driving skills is clear, even with early AD. Voluntary changes in driving behaviors -- such as avoiding driving at night and in bad weather, reducing speed, sticking to familiar routes and limiting distances -- may compensate for that impairment and mitigate the risk of a fatal automobile accident early in the course of AD. However, people with AD and their family members should discuss the risks of continued driving with their doctor.

Falls and Hip Fracture

AD causes unsteadiness in standing and walking, increasing the risk for falls and severe injuries. Head injury resulting from a fall may result in fatal brain bleeding or swelling. Falls also commonly lead to hip fracture. A study published in November 2011 in "Age and Ageing" found that hip fracture was 3 times more common among people with AD older than age 50, compared to those in the same age group without the disease. The authors also noted that the risk of death from hip fracture was increased among people with AD.

Other Causes

People with advanced AD often exhibit behaviors that can put them in potentially life-threatening situations. Wandering away from home and getting lost, which occur commonly in people with AD, can lead to death due to exposure to the elements, accidents or vulnerability to violence. Memory problems can also lead to fatal in-home casualties, such as setting fire to the home by leaving an unattended pot on the stove.

Reviewed and revised by: Tina M. St. John, M.D.

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