Alzheimer’s disease (AD), is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death. It was first described by German psychiatrist and neuropathologist Alois Alzheimer in 1906 and was named after him. Most often, AD is diagnosed in people over 65 years of age, although the less-prevalent early-onset Alzheimer’s can occur much earlier. In 2006, there were projected to be about 26.6 million people worldwide with AD. Alzheimer’s is predicted to affect 1 in 85 people globally by 2050.

Although Alzheimer’s disease develops differently for every individual, there are many common symptoms. Early symptoms are often mistakenly thought to be ‘age-related’ concerns, or manifestations of stress. In the early stages, the most common symptom is difficulty in remembering recent events, known as short term memory loss. When AD is suspected, the diagnosis is usually confirmed with tests that evaluate behavior and thinking abilities, sometimes followed by a brain scan if available, however, examination of brain tissue is required for a definitive diagnosis. As the disease advances, symptoms can include confusion, irritability, aggression, mood swings, trouble with language, and long-term memory loss. As the person’s condition declines they often withdraw from family and society. Gradually, bodily functions are lost, ultimately leading to death. Since the disease is different for each individual, predicting how it will affect the person is difficult. AD develops for an unknown and variable amount of time before becoming fully apparent, and it can progress undiagnosed for years. On average, the life expectancy following diagnosis is approximately seven years. Fewer than 3% of individuals live more than 14 years after diagnosis.

AD is classified as a neurodegenerative disorder. The cause and progression of the disease are not well understood; it is associated with plaques and tangles in the brain. Current treatments only help with the symptoms of the disease. There are no available treatments that stop or reverse the progression of the disease. As of 2012, more than 1,000 clinical trials have been or are being conducted to test various compounds in AD. Mental stimulation, exercise, and a balanced diet have been suggested as ways to delay cognitive symptoms (though not brain pathology) in healthy older individuals, but there is no conclusive evidence supporting an effect.

Because AD cannot be cured and is degenerative, the affected person increasingly relies on others for assistance. The role of the main caregiver is often taken by the spouse or a close relative. Alzheimer’s disease is known for placing a great burden on caregivers; the pressures can be wide-ranging, involving social, psychological, physical, and economic elements of the caregiver’s life. In developed countries, AD is one of the most costly diseases to society.