Memory loss: a thin line between “normal” and “abnormal”?

The author is a geriatrician, epidemiologist and researcher at the Center hospitalier de l'Université de Montréal. He is also one of the co-founders and the medical expert of the company Eugeria, whose mission is to improve the daily lives of people with Alzheimer's disease.

A patient, worried about suffering from dementia, presents for a memory evaluation. After an exhaustive evaluation of his cognitive functions, three diagnostic possibilities are offered to the geriatrician: normal aging, a minor neurocognitive disorder or a major neurocognitive disorder (commonly called dementia). The evaluation reveals new and important memory difficulties: a forgotten recent trip, several unpaid accounts. A diagnosis of dementia attributable to Alzheimer's disease falls. But the patient retorts with a lot of repartee: “You say that I have Alzheimer's disease, but I don't forget any more than my friends of my age. Memory is a faculty that forgets. It's normal to forget, right? »

“Is this normal? is a question that embarrasses me a lot, as a geriatrician. The expected answer is a straightforward yes or no, but the full answer, the one I would like to give, is “it depends”. What are the foundations of normality? And what are its limits? Even if the diagnosis seems very clear-cut, the truth is more complex.

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Beyond the philosophical aspect, “is this normal? is a practical question, because the distinction between normality and abnormality has implications at the personal (how we perceive ourselves), medical (what we diagnose and treat as illnesses) and societal (what we cares, what we accept or ignore). At least four elements can enlighten us: the functional impact of cognitive changes, statistics, the existence of medical treatment and social construction.

The functional impact

Currently, a diagnosis of major neurocognitive disorder (and therefore dementia) requires that the autonomy of a person's activities be reduced. This is the case, for example, when a patient loses the ability to work, drive or manage accounts.

It should be understood that it is through the consequence of cognitive changes that the presence of a “major” neurocognitive disorder is determined. If the changes do not interfere with autonomy, we speak of a “minor” neurocognitive disorder.

This way of distinguishing what constitutes a disease (an abnormal manifestation) by its incidences is unusual, but it is not the prerogative of cognitive disorders. It is also used in psychiatry, if we think of depression or generalized anxiety disorder, for example.

There is a wisdom in the idea of ​​waiting for the functional impact before concluding that a phenomenon is pathological. To paraphrase an English expression, if it ain't broken, why fix it? However, this is not the norm: most of the time in medicine, we repair before waiting for the breakage. One does not wait for incapacitating shortness of breath to diagnose pneumonia, or obstruction before diagnosing colon cancer.

Statistics

The data is a powerful tool in distinguishing normal from abnormal, since the difference between normal aging and mild cognitive impairment rests on the presence of significant cognitive decline compared to what is expected for a person.

This is where the statistics come into play: if a person's memory deviates from the average of their peers according to age, sex and education, we will speak of a minor neurocognitive disorder rather than a normal aging.

However, despite the aura of objectivity it confers, the statistical perspective of normality is not flawless. First, because there will always be people whose characteristics deviate from the average, without them being “abnormal”. Then, because it is not easy to choose the reference group against which to compare the individual. A high performer will remain within the norm for a long time despite a decline when compared to the average of a group of low performers. In such a situation, it may be better to compare the person to himself rather than to an arbitrary group.

Finally, even if we know that approximately one-third of people aged 85 and over have a neurocognitive disorder and that nearly half of us will suffer from cancer during our lifetime, this does not make the disorders cognitive and “normal” cancers.

The existence of medical treatment

The practice of medicine involves taking action to improve the health of patients. What excites doctors (and interests the pharmaceutical industry) are the conditions for which there is a cure. Of course, the existence of a treatment is closely linked to social considerations. Cures will only be discovered for the “diseases” in which we are interested. And once a treatment has been found for an ailment, diagnosing it and proposing a treatment immediately gives it the status of disease, and therefore of an abnormal state. The existence of a treatment is why a pulmonologist will not wait for incapacitating shortness of breath to order antibiotics for bacterial pneumonia, or why a surgeon will not wait for the obstruction to remove a cancerous mass in the colon. If there is an effective intervention for a particular health condition, there is no need to rely on consequences to determine the normality of that condition.

Regarding cognitive disorders, certain drugs can reduce the decline when prescribed at the stage of major neurocognitive disorder. However, there is still no approved treatment in Canada for minor neurocognitive disorder. As a geriatrician, even if it is sometimes obvious that a person is affected beyond the "normal", it is impossible for me to offer him a drug at this stage when there is no functional impact. Waiting before considering the person as “sick” then makes sense, despite the statistical discrepancy and the pathological process already present.

Social construction

Although it may seem surprising, what medicine considers normal or abnormal also depends on how society views a particular condition and the state of knowledge.

In the time of our grandparents' grandparents, no one had “Alzheimer's disease”…because it had not been described. Suffering from dementia as you age was one of the problems that were not then called illnesses, but rather “normal” fatalities that we had to live with. Today, a geriatrician or a neurologist can diagnose Alzheimer's with good certainty: the disease is recognized with its symptoms, signs and diagnostic criteria. But the line between what society considers normal or pathological is sometimes much more blurred. For example, it is not uncommon for older people to become depressed because they are bored, regret the time spent, or lose friends. A temporary depression is absolutely not a depression, and nothing scientifically proves that it is an illness. However, under pressure from pharmaceutical companies, doctors are now tempted to treat this depression with antidepressants, and patients are demanding these drugs. It's the era that wants that! The same is true when talking about age-related cognitive decline: what the doctor and the patient consider normal or pathological depends on what society as a whole tends to find "normal". Would you say, for example, that rowing over difficult crossword puzzles when you are 90 years old is normal? There will always be a social dimension to what is judged to be a disease.

So, is it normal to forget? Is it a disease?

To properly answer this question and the patient, we would have to say “yes and no”, and “it depends”. Since there is sometimes no time for nuance, I often allude to these functional, statistical, therapeutic and social perspectives during meetings with my patients and their loved ones. If there is a functional impact, if we base ourselves on a statistical definition, if we can offer a treatment, and if society and the medical profession perceive it as such, forgetting as much is a “disease”.

Still, the line that separates normality from abnormality is both fine and shifting. The multiple perspectives force geriatrics to do a lot of thinking. The moving line is a sign that science is progressing and that there are still many things to discover.