Alzheimer's disease tends to develop 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. They include:

• Preclinical Alzheimer's disease.
• Mild cognitive impairment due to Alzheimer's disease.
• Mild dementia due to Alzheimer's disease.
• Moderate dementia due to Alzheimer's disease.
• Severe dementia due to Alzheimer's disease.

Dementia is a term used to describe a group of symptoms that affect intellectual and social abilities 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. Each person has a different experience with Alzheimer's and its symptoms.

Alzheimer's disease begins long before any symptoms become apparent. This stage is called preclinical Alzheimer's disease. It's usually identified only in research settings. You and those around you won't notice symptoms during this stage.

This stage of Alzheimer's can last for years, possibly even decades. Although you won't notice any changes, new imaging technologies of the brain can identify amyloid plaques and neurofibrillary tangles. The tangles develop when tau proteins change shape and organize into structures. These are hallmarks of Alzheimer's disease.

The ability to identify these early changes is especially important for clinical trials. Ongoing trials are looking at whether treating people with preclinical Alzheimer's may delay or slow the onset of symptoms. The imaging technologies also are important as new treatments are developed for Alzheimer's disease.

Additional biomarkers have been identified for Alzheimer's disease. These are found in blood samples and can indicate an increased risk of disease. These biomarkers can be used to support the diagnosis of Alzheimer's disease, typically after symptoms appear.

Genetic tests also can tell you if you have a higher risk of Alzheimer's disease, particularly early-onset Alzheimer's disease. These tests aren't recommended for everyone. You and your health care provider can discuss whether genetic testing might be helpful for you.

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. People with MCI may have memory lapses when it comes to information that is usually easily remembered. This may include conversations, recent events or appointments.

People with MCI also may have trouble judging the amount of time needed for a task. They may have trouble judging the number or order of steps needed to complete a task. The ability to make sound decisions can become harder.

Not everyone with mild cognitive impairment has Alzheimer's disease. MCI is often diagnosed based on a health care provider's review of symptoms and professional judgment. But if necessary, 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. This is when it becomes clear to family and doctors that a person is having significant trouble with memory and thinking. The symptoms impact daily functioning.

In the mild dementia stage, people may experience:

• Memory loss of recent events. Individuals may have a hard time remembering newly learned information. They may ask the same question over and over.
• Trouble 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. They may be irritable or angry when that's not typical for them. Reduced motivation to complete tasks also is common.
• Trouble organizing and expressing thoughts. At this stage, people may not be able to find the right words to describe objects. They may have trouble clearly expressing ideas.
• 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 dementia stage of Alzheimer's disease, people grow more confused and forgetful. They begin to need more help with daily activities and self-care.

People with the moderate dementia stage of 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 behaviors make it unsafe to leave them on their own.

• Experience even greater memory loss. People may forget details of their personal history, such as their address, 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. They may need help choosing proper clothing for the occasion or the weather. People in this stage also may need assistance with bathing, grooming, using the bathroom and other self-care. Some may occasionally lose control of their bladder or bowel movements.

• Undergo significant changes in personality and behavior. It's not unusual for people in the moderate dementia stage to develop unfounded suspicions. For example, they might become convinced that friends, family or professional caregivers are stealing from them. Or they may accuse a spouse of 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 late stage of the disease, called severe dementia due to Alzheimer's disease, mental function continues to decline. The disease also has a growing impact on movement and physical capabilities.

In late-stage severe dementia due to Alzheimer's disease, people generally:

• Lose the ability to communicate. Individuals can no longer converse or speak in ways that make sense. They may only 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. People in this stage may become unable to walk without assistance. They may even be unable to sit or hold up their 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 between three and 11 years after diagnosis. But some live 20 years or more. The degree of impairment at diagnosis can affect life expectancy. Untreated vascular risk factors such as hypertension are associated with a faster rate of progression of Alzheimer's disease.

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, falls and other infections.