How Fast Does Mild Cognitive Impairment Progress?

Getting diagnosed with mild cognitive impairment (MCI) can be scary. For many people, the first questions that come to mind are, “How long do I have before I’ll be in full-blown dementia? How rapid will be my decline? How fast does mild cognitive impairment progress to dementia?”

Some people ask their doctors for a timetable, seeking to understand what cognitive changes to expect next month, six months from now, a year from now, and so on. Unfortunately, few aspects of medicine are that precise, and MCI is a particularly difficult condition when it comes to making predictions. Learning more about the nature of MCI can help you formulate a realistic set of expectations about what is even possible to know regarding the condition’s relationship to dementia.

A State, Not a Stage

Inquiries about an “MCI progression timeline” are certainly understandable. A person may have been told that MCI refers to cognitive decline not severe enough to interfere with independent living. But what they might not know is that MCI doesn’t necessarily describe a stage in a progressive disease process that always culminates in dementia. Instead, it describes a state, or level, of cognition which may worsen, stay the same, or even get better.

Thus, the mere fact of having MCI doesn’t mean you will go on to develop dementia. In other words, the truest answer to the question, “How fast does MCI progress?” is a perhaps-disappointing, “Sometimes very quickly, sometimes very slowly, and sometimes not at all.” Let’s look more closely at what we know about the progression of MCI into dementia.

How Common is Progression?

Current estimates are that, among all people newly diagnosed with MCI, 10%-15% will develop dementia within one year, and 33% will be diagnosed with Alzheimer’s specifically within five years. However, that’s a very broad statement that lumps together patient-types who are unlikely ever to develop dementia with those who probably will.

Progression and Underlying Cause

Treatment guidelines for MCI indicate that among people 65 and older, the condition progresses to dementia in around 15% of cases, and the chances of progression are different depending on the cause of the MCI. Obviously, it’s impossible to say with certainty that an individual will never develop Alzheimer’s or another form of dementia. However, MCI cases may be divided into four broad categories that, with varying degrees of certainty, can shape our expectations about whether the MCI is likely to go on to become dementia.

• MCI from brain injury.In these cases, some injury to the brain is the direct cause of the MCI. Examples could include a combat wound, repeated concussions from sports, brain changes from substance abuse, lingering damage from a high fever, or the aftereffects of a stroke. Such cases may remain stable or may develop into non-Alzheimer’s forms of dementia such as vascular dementia or chronic traumatic encephalopathy (CTE). Moderate and severe traumatic brain injuries increase the lifetime risk of dementia by 200%-400%. And in the year following a stroke, a person’s risk of dementia triples, then recedes slightly but remains elevated for 20 years. What is more difficult to assess is how many of these people will experience a period of MCI that then progresses to dementia and, for those who do, how rapid that progression will be.

• MCI from treatable conditions.Sometimes MCI is caused by the side effects of medication, untreated sleep apnea, depression or anxiety, hormonal imbalances, or nutritional deficiencies. In most such cases, rather than progressing to dementia, the mild cognitive impairment symptoms improve once the underlying condition is addressed. But this doesn’t rule out that some people in this category will ever develop dementia, especially if the condition has gone untreated for a prolonged period before finally being addressed.

• MCI of unknown origin.For these people, there is no obvious indication that the MCI is caused by brain injury, by a treatable underlying condition, or by dementia disease. The MCI may simply result from the kinds of brain changes that are a normal part of aging, just in a more severe form, and they could either stabilize or progress to dementia…and that progression could happen rapidly, within just a few months of the MCI diagnosis, or could take several years.

• MCI due to dementia disease.Sometimes through testing and scans performed on people with MCI, physicians can identify signs of the brain changes associated with dementia diseases such as Alzheimer’s. Such cases, typically labeled “MCI due to Alzheimer’s,” may be thought of as a kind of pre-dementia since the person has not yet lost their ability to perform their daily functions independently. The likelihood of progression to dementia is much higher for people who fall into this category, and yet it’s still not an absolute certainty. While it might be reasonable to expect a person with MCI due to Alzheimer’s to develop dementia within one or two years, some defy expectations by possessing the disease pathology of Alzheimer’s while remaining indefinitely at a cognitive level more appropriately labeled as MCI.

Looking Ahead

Fortunately or unfortunately, there is no timetable for the rate at which MCI will develop into dementia. That’s because MCI is not a specific disease but rather a state of impairment which could be caused by any of several factors. Whether, and how fast, MCI will progress to dementia can be influenced not just by its cause, but by the person’s age, by genetic factors, overall health, and the presence of other conditions such as high blood pressure and cardiovascular disease. The idiosyncratic nature of MCI makes it extremely difficult to predict. But within that uncertainty lies the hope that an individual’s case might never worsen. That’s all the more reason to act quickly by working with your doctor on a plan to keep dementia at bay. Research suggests that making lifestyle changes such as exercise, smoking cessation, an improved diet, stress reduction, and better sleep can help with your MCI symptoms and delay or prevent its development into dementia.