Mild cognitive impairment (MCI) is an easily misunderstood term. Often when people hear it, they assume that it’s a general descriptor for minor memory problems. Others guess that it’s the official term for early Alzheimer’s disease. Still others believe it describes the normal age-related memory loss that most people can expect to experience after middle age. None of these is quite correct.
Rather than a general layperson’s description, MCI has a specific clinical meaning. It contains these principal elements:
A person may progress from normal age-related memory loss to MCI, and then to some form of dementia, but these conditions are not necessarily linked sequentially. Understanding the relationship of MCI to dementia is complicated by the fact that some MCI patients have indicators of Alzheimer’s disease, leading to a diagnosis of “MCI due to Alzheimer’s disease.” But it’s critical to understand that this represents a minority of MCI patients. For most, their MCI cannot be tied directly to Alzheimer’s and may never progress to dementia.
Around 15%-20% of Americans aged 65 or older meet the criteria for MCI, and this population breaks down into thirds…one third recover from their MCI, one third remain stable in their MCI, and one third go on to develop dementia. It’s difficult to pin down an average age for mild cognitive impairment, but a 2020 study estimates that two out of three Americans will experience some level of cognitive impairment at an approximate average age of 70 years. And the American Academy of Neurology estimates that 6% of people in their 60s have MCI and that 37% of people will have MCI by the time they reach age 85.
Mild cognitive impairment is not the same thing as moderate cognitive impairment. On the Cognitive Performance Scale used by clinicians, people who score a 2 are diagnosed with mild cognitive impairment and those who score a 3 are diagnosed with moderate cognitive impairment. This article pertains only to mild cognitive impairment.
When most people hear the term “mild cognitive impairment,” they immediately think of memory problems. However, MCI can affect both memory and other aspects of thinking. In fact, experts now recognize two types of MCI based on the cognitive skills affected. Amnestic MCI is mild cognitive impairment principally affecting memory. Nonamnestic MCI primarily affects other aspects of cognition, including visual perception, judgment, decision-making, and the ability to perform complex tasks.
When people with MCI undergo cognitive testing, they often struggle to recall details after being shown photographs or drawings. Some have a hard time remembering what words or other details appeared in a block of text they’ve been asked to read.
Life with MCI can be frustrating and difficult. However, most symptoms do not present a significant danger, and, by definition, people with MCI remain able to live independently. (If the symptoms make independent living impossible, the diagnosis is upgraded to dementia). An person with MCI might take a wrong turn walking to a colleague’s office in the same building where they’ve worked for years. They might find themselves going back over a show they’re watching because they realize they’ve completely lost track of the plot. They might miss dinner with friends because they’ve forgotten they were invited. They might pull up a YouTube tutorial on how to change their kitchen faucet but find themselves unable to follow instructions that would have been simple to them a few years ago. They may annoy drivers behind them for hesitating too long to enter an intersection after a stop sign. They may decide one month to double up on their mortgage payment even though it nearly empties their checking account.
Another unfortunate aspect of MCI is the possibility of noticeable changes to mood and personality. People with MCI may become irritable or aggressive, anxious, or depressed. It’s not uncommon for someone with MCI to suddenly abandon hobbies or interests that were once consuming passions. Some of these psychological symptoms may relate directly to the structural changes going on in their brain, while others could be a very understandable emotional response to the frustration and sense of loss that comes with living with MCI.
In cases of MCI due to Alzheimer’s disease, we know that the mild cognitive impairment is driven by the same brain changes observed in Alzheimer’s. We also typically know when MCI has been caused by injury to the brain in some form. But for general MCI without these obvious underpinnings, researchers still aren’t completely sure about the causes. The primary risk factors appear to be advancing age and family history of cognitive decline.
In recent years, cardiovascular disease has also emerged as a significant risk factor for MCI. People with heart disease are more likely than the general population to have MCI. For example, one 2023 study estimates that as many as 81% of heart failure patients may suffer from cognitive impairment. This link may be due to cardiovascular disease’s deleterious effects on the brain, or it may be because cardiovascular disease and MCI appear to share several risk factors, such as high blood pressure, diabetes, smoking, obesity, and a sedentary lifestyle. Experts believe that modifying those risk factors could help prevent both conditions and, in fact, can help people with their MCI symptoms.
When a person realizes that their cognitive decline has gone beyond normal age-related memory loss, they often initiate a dialogue with their primary care doctor to express their concerns. The physician will then typically conduct a workup that includes a full medical history including careful documentation of all the current symptoms that have the person concerned. Because cognitive problems can be caused by medications, sleep issues, hormonal imbalances, and vitamin deficiencies, the doctor will take care to rule these out. And because it’s often difficult to objectively assess our own cognition, usually a close loved one will be asked to share their observations about any recent cognitive changes.
The physician will then perform a brief cognitive screening test as well as a simple neurological evaluation to see if the person has normally functioning reflexes, coordination, and balance, and will order blood tests and a brain scan to look for structural changes that could be indicative of dementia or brain injury. If no obvious cause of cognitive decline is discovered, the person will be referred to a specialist who can perform more involved neuropsychological testing to arrive at a diagnosis.
