Alzheimer's disease can last more than a decade. See what types of behaviors are common in each of the stages as the disease progresses.

By Mayo Clinic Staff

Alzheimer's disease tends to develops slowly and gradually worsens over several years. Eventually, Alzheimer's disease affects most areas of your brain. Memory, thinking, judgment, language, problem-solving, personality and movement can all be affected by the disease.

There are five stages associated with Alzheimer's disease: preclinical Alzheimer's disease, mild cognitive impairment due to Alzheimer’s disease, mild dementia due to Alzheimer's, moderate dementia due to Alzheimer's and severe dementia due to Alzheimer's. Dementia is a term used to describe a group of symptoms that affect intellectual and social abilities severely enough to interfere with daily function.

The five Alzheimer's stages can help you understand what might happen, but it's important to know that these stages are only rough generalizations. The disease is a continuous process. Your experience with Alzheimer's, its symptoms and when they appear may vary.

Alzheimer's disease begins long before any symptoms become apparent. This stage is called preclinical Alzheimer's disease. You won't notice symptoms during this stage, nor will those around you.

This stage of Alzheimer's can last for years, possibly even decades. Although you won't notice any changes, new imaging technologies can now identify deposits of a protein called amyloid beta that is a hallmark of Alzheimer's disease. The ability to identify these early deposits may be especially important in the future as new treatments are developed for Alzheimer's disease.

Additional biomarkers — measures that can indicate an increased risk of disease — have been identified for Alzheimer's disease. These biomarkers can be used to support the diagnosis of Alzheimer's disease, typically, after symptoms are evident.

There are also genetic tests that can tell you if you have a higher risk of Alzheimer's disease, particularly early-onset Alzheimer's disease. As with newer imaging techniques, biomarkers and genetic tests will become more important as new treatments for Alzheimer's disease are developed.

People with mild cognitive impairment have mild changes in their memory and thinking ability. These changes aren't significant enough to affect work or relationships yet. People with MCI may have memory lapses when it comes to information that is usually easily remembered, such as conversations, recent events or appointments.

People with MCI may also have trouble judging the amount of time needed for a task, or they may have difficulty correctly judging the number or sequence of steps needed to complete a task. The ability to make sound decisions can become harder for people with MCI.

Not everyone with mild cognitive impairment has Alzheimer's disease. The same procedures used to identify preclinical Alzheimer's disease can help determine whether MCI is due to Alzheimer's disease or something else.

Alzheimer's disease is often diagnosed in the mild dementia stage, when it becomes clear to family and doctors that a person is having significant trouble with memory and thinking that impacts daily functioning.

In the mild Alzheimer's stage, people may experience:

  • Memory loss for recent events. Individuals may have an especially hard time remembering newly learned information and ask the same question over and over.
  • Difficulty with problem-solving, complex tasks and sound judgments. Planning a family event or balancing a checkbook may become overwhelming. Many people experience lapses in judgment, such as when making financial decisions.
  • Changes in personality. People may become subdued or withdrawn — especially in socially challenging situations — or show uncharacteristic irritability or anger. Reduced motivation to complete tasks also is common.
  • Difficulty organizing and expressing thoughts. Finding the right words to describe objects or clearly express ideas becomes increasingly challenging.
  • Getting lost or misplacing belongings. Individuals have increasing trouble finding their way around, even in familiar places. It's also common to lose or misplace things, including valuable items.

During the moderate stage of Alzheimer's disease, people grow more confused and forgetful and begin to need more help with daily activities and self-care.

People with moderate Alzheimer's disease may:

  • Show increasingly poor judgment and deepening confusion. Individuals lose track of where they are, the day of the week or the season. They may confuse family members or close friends with one another, or mistake strangers for family.

    They may wander, possibly in search of surroundings that feel more familiar. These difficulties make it unsafe to leave those in the moderate Alzheimer's stage on their own.

  • Experience even greater memory loss. People may forget details of their personal history, such as their address or phone number, or where they attended school. They repeat favorite stories or make up stories to fill gaps in memory.
  • Need help with some daily activities. Assistance may be required with choosing proper clothing for the occasion or the weather and with bathing, grooming, using the bathroom and other self-care. Some individuals occasionally lose control of their bladder or bowel movements.
  • Undergo significant changes in personality and behavior. It's not unusual for people with moderate Alzheimer's disease to develop unfounded suspicions — for example, to become convinced that friends, family or professional caregivers are stealing from them or that a spouse is having an affair. Others may see or hear things that aren't really there.

    Individuals often grow restless or agitated, especially late in the day. Some people may have outbursts of aggressive physical behavior.

In the severe (late) stage of Alzheimer's disease, mental function continues to decline, and the disease has a growing impact on movement and physical capabilities.

In severe Alzheimer's disease, people generally:

  • Lose the ability to communicate coherently. An individual can no longer converse or speak coherently, although he or she may occasionally say words or phrases.
  • Require daily assistance with personal care. This includes total assistance with eating, dressing, using the bathroom and all other daily self-care tasks.
  • Experience a decline in physical abilities. A person may become unable to walk without assistance, then unable to sit or hold up his or her head without support. Muscles may become rigid and reflexes abnormal. Eventually, a person loses the ability to swallow and to control bladder and bowel functions.

The rate of progression for Alzheimer's disease varies widely. On average, people with Alzheimer's disease live eight to 10 years after diagnosis, but some survive 20 years or more.

Pneumonia is a common cause of death because impaired swallowing allows food or beverages to enter the lungs, where an infection can begin. Other common causes of death include dehydration, malnutrition and other infections.

Nov. 24, 2015