According to the Centers for Disease Control and Prevention, Alzheimer disease is the sixth most common cause of death in the United States. AD is 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.
As AD progresses, the abilities to walk, sit upright and swallow correctly decrease. Lack of mobility diminishes the capacity of the lungs to expand and manage secretions properly, increasing susceptibility to pneumonia. Poorly coordinated swallowing allows foods, liquids and saliva to enter the airway, causing a particularly aggressive form of pneumonia. Pneumonia may be the final complication, but AD is the cause of death in these situations.
Dehydration and Malnutrition
Difficulty in swallowing, loss of interest in food and liquids and inability to express hunger or thirst -- all of which are caused by AD -- may decrease intake below the level necessary for normal organ function. Many serious and ultimately fatal problems can result, including kidney failure, coma, the formation of bed sores, inadequate heart function and reduced resistance to infection.
There are conflicting studies regarding the risk of fatal car accidents among drivers with AD, but the evidence of impaired driving skills, even in early AD, is clear. 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 injuries resulting from a fall may cause fatal brain bleeding or swelling. Falls also commonly lead to hip fracture. A 2011 article published in "Age and Ageing" noted that hip fracture was 3 times more common in people with AD compared to people without the disease. The authors also noted that the risk of death from hip fracture was increased among people with AD.