Alzheimer's Disease

What is Alzheimer's Disease?

Alzheimer’s disease (AD) is an irreversible, progressive brain disorder that slowly destroys memory and thinking skills, and, eventually, the ability to carry out the simplest tasks. Alzheimer’s disease is the most common cause of dementia among older adults.1 Dementia is the loss of cognitive functioning (thinking, remembering, and reasoning) and behavioral abilities to such an extent that it interferes with a person’s daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’s functioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living.

The cause(s) of Alzheimer’s disease are poorly understood. In people with early-onset Alzheimer’s disease, a genetic mutation may be the cause. Late-onset Alzheimer’s disease arises from a complex series of brain changes that occur over decades. The causes probably include a combination of genetic, environmental, and lifestyle factors.1 The importance of any one of these factors in increasing or decreasing the risk of developing Alzheimer’s disease may differ from person to person.

Pathological changes in the brain are thought to begin a decade or more before memory and other cognitive problems appear in Alzheimer’s disease patients. During this pre-symptom stage, people seem to be symptom-free, but toxic changes are taking place in the brain. Abnormal deposits of proteins form amyloid plaques and tau tangles throughout the brain. Once-healthy neurons stop functioning, lose connections with other neurons, and die.

What are the Stages of Alzheimer's Disease?

The progress of Alzheimer’s disease can be divided into four stages:

  1. Predementia – the first symptoms of Alzheimer’s disease appear and are frequently mistaken for aging or stress.

  2. Mild Alzheimer’s disease – increasing impairment of learning and memory eventually leads to a definitive diagnosis. Problems can include wandering and getting lost, trouble handling money and paying bills, repeating questions, taking longer to complete normal daily tasks, and personality and behaviour changes.

  3. Moderate Alzheimer’s disease – in moderate Alzheimer’s disease, progressive deterioration eventually hinders independence, with subjects being unable to perform most common activities of daily living. In this stage, damage occurs in areas of the brain that control language, reasoning, sensory processing, and conscious thought. Memory loss and confusion grow worse, and people begin to have problems recognizing family and friends. They may be unable to learn new things, carry out multi-step tasks, such as getting dressed, or cope with new situations.

  4. Severe Alzheimer’s disease – during the final stages of Alzheimer’s disease, the patient is completely dependent upon caregivers. Language is reduced to simple phrases or even single words, eventually leading to complete loss of speech. People with Alzheimer’s disease will ultimately not be able to perform even the simplest tasks independently; muscle mass and mobility deteriorates to the point where they are bedridden and unable to feed themselves.

Current Treatments and Unmet Needs

Currently there are no pharmacologic treatments available for Alzheimer’s disease that will slow or stop the damage and destruction of neurons that cause its symptoms.

In the U.S. the drugs that are approved for the treatment of Alzheimer’s disease may temporarily improve symptoms, either by increasing the amount of chemicals called neurotransmitters in the brain or by blocking certain receptors in the brain from excess stimulation that can damage nerve cells. The effectiveness of these drugs varies from person to person and is limited in duration.2

Alzheimer's Disease Facts and Figures

  • In the U.S., there were approximately 5.8 million patients living with Alzheimer’s disease in 2019.2

  • Worldwide, at least 50 million people are believed to be living with Alzheimer’s disease or other dementias.3

  • Alzheimer’s disease is the 6th leading cause of death among U.S. adults.4

  • More than 16 million Americans, usually family and friends, provide unpaid care for someone with Alzheimer’s disease or other dementias.5

  • In 2018, caregivers of people with Alzheimer’s disease or other dementias provided an estimated 18.5 billion hours of informal (unpaid) assistance, a contribution to the nation valued at $233.9 billion.2

  • In 2019, the estimated total payments for all individuals with Alzheimer’s disease or other dementias was estimated at $290 billion. Medicaid and Medicare are expected to cover 67% of these costs.2


  1. Alzheimer’s Disease Fact Sheet. National Institute on Aging. Https:// Accessed March 17, 2020.
  2. Alzheimer’s Association. (2019). 2019 Alzheimer’s disease facts and figures. Alzheimer’s & Dementia 15, 321–387.
  3. Patterson, C. (2018). World Alzheimer Report 2018 – The state of the art of dementia research: New frontiers. Alzheimer’s Disease International 48.
  4. Xu, J., Kochanek, K.D., Murphy, S.L., and Tejada-Vera, B. (2010). Deaths: Final Data for 2007. National Vital Statistics Reports 58, 135.
  5. Riffin, C., Van Ness, P.H., Wolff, J.L., and Fried, T. (2017). Family and Other Unpaid Caregivers and Older Adults with and without Dementia and Disability. J Am Geriatr Soc 65, 1821–1828.