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Does Mild Cognitive Impairment Convert to Alzheimer's Disease?

  • This question is commonly posed in the press, discussed at academic conferences, and debated by physicians grappling to choose a course of clinical care. Despite the centrality of this question in so many forums of cognitive health, it is a nonsensical inquiry with inherent flaws.

    There are many medical conditions that can cause a subtle cognitive deficit. Pondering whether or not mild cognitive impairment (MCI) will "convert" to Alzheimer's Disease (AD) obscures the fact that MCI is a symptom of an underlying medical problem, not the problem itself. In fact, some MCI is actually caused by AD and therefore, the prospect of converting does not belong in a logical, informed discussion.

    The Correct Question

    When MCI is present, we should not ask if or when it will convert to AD. The correct question is: What is the cause of the impairment?

    If the answer to the correct question is "AD", then the folly of a conversion outcome is clear; the disease precedes the impairment and not vice-versa. If the MCI is caused by some other medical condition (depression, vascular disease, thyroid disease, anxiety, etc.) then it is equally futile to consider whether or not it will convert to AD; these medical problems are separate and distinct.

    That is not to say that a person with MCI caused by untreated depression will never get AD because they may. In fact, some medical conditions that can cause MCI confer a greater risk for AD. Nonetheless, the notion of "converting" from MCI to AD is illogical.

    We Get it Right With Other Diseases

    A good analogy would be to learn of a patient with excessive thirst and blurry vision and then wonder if these symptoms will ever "convert" to Diabetes. Most physicians would perform a diagnostic work-up, take note of the blood sugar, and then either diagnose diabetes or rule it out immediately. There would be no debate about whether or not the symptoms would eventually covert to diabetes.

    We must do the same with MCI. That is, perform a work-up and identify the underlying cause of the symptoms so that the patient may benefit from timely, appropriate treatment.

    The Need for Clarity

    The perpetration of the idea that MCI might or might not convert to AD causes some primary care physicians to take a "wait and see" attitude. In those cases, it prevents them from proactively diagnosing the cause of the MCI and treating it. Giving any credence to the notion that MCI is a sporadically progressive precursor to AD is a barrier to clarity and interferes with a higher standard of care in this field.

    Given that, on average, AD is diagnosed 8-10 years after the onset of the earliest clinical symptoms, improvements in the timeliness of intervention is our most immediately graspable improvement for care in this field. There is no doubt that misconceptions which delay early diagnosis of Alzheimer's disease cause needless suffering.