Central Nervous System
Alzheimer disease is principally a disease of the central nervous system, which includes the brain and spinal cord. Although the cause of Alzheimer disease remains poorly understood, specific brain abnormalities have been identified in patients with the disorder. Amyloid plaques, composed of specific proteins and pieces of dead brain cells, progressively accumulate in the brain tissue. A naturally occurring brain protein known as tau also accumulates abnormally, causing brain cells to malfunction and eventually die.
The loss of functioning brain tissue that occurs with Alzheimer disease initially causes problems with memory and learning. As the disease progresses, intellectual function, personality and mood are increasingly affected. With late-stage disease, patients lose their sense of self and present circumstances. Patients with advanced Alzheimer disease are completely dependent on others for daily care, as they have forgotten how to go about the most basic tasks of daily living. Patients do not recognize loved ones and lose the capacity to contemplate, plan, rationalize, organize and interact with their environment.
Alzheimer disease adversely affects the digestive system in several ways. According to a review published in 2013 in the "Archives of Gerontology and Geriatrics," swallowing difficulties commonly occur in Alzheimer disease, and compared to other types of dementia, these difficulties often occur fairly early in the disease. People often have difficulty eating without choking. Pneumonia remains a common cause of death among people with Alzheimer disease. The onset of pneumonia is frequently associated with swallowing difficulties that lead to the accidental entry of food or liquids into the airways.
People living with Alzheimer disease may develop an impaired sense of smell, which also interferes with the sense of taste. Eating may become problematic due to these impairments. Bowel control is also adversely affected with Alzheimer disease. Fecal incontinence occurs in most people with advanced disease.
People with advanced Alzheimer disease lose the ability to use their muscles in purposeful ways. Patients with late-stage disease typically lose their ability to walk. The ability to maintain posture to sit safely in a chair may also be lost. The muscles become increasingly rigid as control of the neuromuscular system declines. Accidental injuries related to declining motor function are common among people with Alzheimer disease.