Alzheimer’s disease does not develop suddenly. It emerges over the course of decades. There is a history of short-term memory loss that often dates back a decade before more obvious symptoms arise. Onset is subtle. How many of us have had senior moments? How do we know if they are benign or the hallmark of progressive cognitive decline? Changes are complex and differ across individuals depending on the region of the brain that is affected.

One way to make sense of these complicated pathways is to have a category that reflects significant changes in memory that fall short of a dementia. The solution has been to create a category – diagnosis if you like – for individuals who have memory changes but are not demented. This is Mild Cognitive Impairment (MCI) (“Mild cognitive impairment and mild dementia: a clinical perspective,” David Knopman and Ronald Peterson, Mayo Clinic Proceedings, 2014, 89, 1452-1459, PMID 25282431).

MCI (the amnestic type) is memory decline that is greater than the inefficiencies of normal aging. It is marked by cognitive impairment that falls short of a dementia. The afflicted person remains independent but there are concerns as well as performance on objective tests that are lower than expected from those with similar age and education. A person with MCI can still pay bills, shop, and prepare meals. MCI marks the risk of future decline that is greater than for those with normal memory.

How is MCI different from mild dementia? Those with mild dementia also have poorer memory than either those who age normally or those with MCI. Mild dementia is marked by substantial decline at work or at home in abilities such as paying bills, shopping, or taking medications. However, personal care like dressing, preparing snacks, and grooming are fine. Persons with mild dementia almost always decline over time whereas some with MCI do not.

How are these conditions diagnosed? Mostly by a careful history obtained from the person of concern and an informant such as a family member or close friend. Despite the advancements in imaging techniques, a good clinical interview and objective cognitive tests are the gold standard for diagnosing MCI and mild dementias. If these assessments suggest decline further medical evaluation is necessary to determine if the problems are a result of a medical disorder such as stroke, thyroid disorder, or diabetes.

What should you look for in everyday life to indicate that someone may be at risk for progressive decline? Mostly the early signs will show as functional changes. Look at abilities like paying bills, balancing the checkbook, getting taxes ready, managing affairs, organizing papers, being able to shop alone, preparing meals, tracking current events/interests, following movies/TV shows, taking medications, finding one’s way around. If any of these skills are of concern, seek assessment.