What is Alzheimer’s disease?

Alzheimer’s disease is a neurological disorder involving cognitive and functional impairments that almost always worsen with time. The disease is typically first identified by memory loss and forgetfulness, with episodic (personal experiences and events) and semantic (facts and words) memory usually impaired first. Short-term memory also becomes limited, with a smaller capacity and shorter duration. Procedural memory — how to perform functions and tasks — is not affected until much later.^[2][3]

As the disease progresses and different areas of the brain degenerate, additional symptoms develop, including mood changes, difficulty with language, trouble performing basic activities, and, in later stages, an impaired ability to swallow and breathe.

Prior to developing Alzheimer’s disease, individuals first develop a less extreme disorder called mild cognitive impairment (MCI). Although MCI is common during older age (a time when cognitive function declines to some extent), with Alzheimer’s disease, memory problems exceed what is expected based on age. Despite MCI being a risk factor, people who develop the disorder don’t usually progress to Alzheimer’s disease^[4], and there does not seem to be evidence that screening older adults for early MCI is beneficial.^[5]

Once a person is diagnosed with Alzheimer’s disease, the progression of cognitive decline is about a 3-point reduction per year on the 30-point Mini–Mental State Examination (MMSE).^[6][7]