In contrast to what we might think, anosognosia is not a monolithic symptom. It may not only affect different areas depending on the form which it takes, but may also vary as the disease evolves in the same patient, as well as from one patient to another over the course of the same illness. 'The mechanisms which underlie the appearance of anosognosia are still imperfectly understood', indicates Jedidi. 'Of course, psychological factors are involved, but this symptom cannot, however, be assimilated to denial in the psychological or psychiatric sense of the term, such as when someone refuses to accept that they are ill. Ultimately, the major component of anosognosia, whether it be total or partial, is a change in the most elaborate of cognitive functions: self-awareness.'

In Alzheimer's disease, the percentage of anosognosic patients increases as the disease progresses. Despite statistics which may vary widely depending on the study in question, it is generally considered that its frequency is around 10% to 15% of cases at the start and around 40% to 50% at the most severe stages of the disease. This change is explained by the progression of the disease in terms of neuronal degeneration within the cerebral regions involved in the mechanisms of self-awareness.

Warning - danger!

Far from being simplistic, this symptom may also vary in intensity: we thus talk about total or partial anosognosia. In other words, there is a continuum of self-awareness between a healthy patient and the total anosognosia affecting memory, cognitive and behavioural deficits from which a patient may suffer. Thus, a totally anosognosic patient may say, for example: 'Doctor, my friends and family are worrying about nothing, they talk a load of rubbish; I'm just a bit tired.' Another patient with partial anosognosia may say: 'It's true, I do forget some things, but that's just old age - there's nothing we can do about it.'

Couldn’t anosognosia, in some ways, be considered as a blessing for an Alzheimer's patient? The patient's awareness of the slow deterioration of their memory and intellectual faculties or changes in their personality may lead to significant psychological distress. 'Some studies show an inverse relationship, in any case at the start of the illness, between depression and anosognosia, where the most depressed patients are the least anosognostic and the most anosognostic patients are the least depressed', reports Jedidi.

But to conclude from this that anosognosia is a good thing, is a step which the researcher refuses to take. Why? Because, by its very nature, the symptom complicates these patients’ treatment and challenges their own safety and that of their loved ones. They may refuse home help, for example, drive when they are incapable of following the rules of the road, or continue to manage their own finances despite the fact that they no longer have any concept of the value of money.