The normal aging process is associated with many changes in the way the body and the mind function. While changes like age spots or stiffer joints are most noticeable to us, what’s not as noticeable are cognitive changes, which are often gradual but can one day feel seriously disconcerting.

What is considered normal forgetfulness and what is not? Though it can be difficult to discern between memory lapses that naturally occur with aging and more serious lapses that may signal cognitive decline, there are some key differences.

Here we provide an overview of how cognitive health changes with age: from normal and expected changes, to mild cognitive impairment, and signs of a more serious condition like dementia.

Like our bodies, the brain experiences physical changes as we age. Some common changes include loss of volume in the areas responsible for memory and planning, reduced connectivity between brain cells, decreased blood flow in the brain, and an increase in inflammation. These physical brain changes often correlate with slight changes in cognitive function. Normal age-related cognitive decline can show up as subtle changes in certain cognitive areas, and may differ from person to person. Some common examples of this include a slower pace of thinking, and difficulty with paying attention, holding information in the mind, multitasking, finding words, and remembering names.1,2 These cognitive abilities tend to peak around age 30 and decline slowly thereafter. On a brighter note, not all of the cognitive changes associated with aging are negative. Other functions, such as vocabulary, reading, and verbal memory, can remain stable or even improve with age.1

When cognitive changes exceed what is expected in the normal aging process, the decline is typically categorized based on severity as Mild Cognitive Impairment (MCI) or dementia. These terms are used to classify impairment that can result from a variety of underlying causes. With MCI, the decline in cognition is more severe than what would be expected for someone’s age but it does not interfere with their ability to do everyday activities. For example, someone with MCI may forget important events like appointments or start to feel overwhelmed by making decisions. People with MCI are at higher risk for developing dementia than people without it, but not everyone with MCI progresses to dementia.

Dementia is a broad term used to describe a decline in cognition that is more severe than would be expected for someone’s age and that is serious enough to interfere with their ability to do everyday activities. Alzheimer’s disease (AD) is the most common cause of dementia, representing 60-80% of cases, but other causes can include conditions like vascular dementia and Parkinson’s disease. AD is associated with large, widespread losses of neurons in the brain. The cell death begins in the regions associated with memory, such as the hippocampus, and spreads to other areas from there, such as those needed for language, reasoning, and social behavior. AD also disrupts communication between neurons, as well as metabolism and repair. Someone with AD may experience problems with handling money or navigating around familiar places, and may repeat themselves frequently.

In summary, certain types of cognitive changes are expected throughout the aging process whereas more severe impairments can be a cause for concern. It can sometimes be difficult to determine where some changes, like difficulty with remembering names or losing the train of thought, fall on the spectrum. Anyone who is worried about the state of their cognitive health should monitor themselves through regular assessments or talk to their doctor about a professional evaluation.