Ten-Year Advanced ‘Warning’ of Alzheimer’s Disease?

Changes in the brain can happen a long time before a person starts to show symptoms.  This is demonstrated by a study published online in the journal Neurology.  It seems that the thickness of the cerebral cortex – the outer grey matter layer of the brain - is linked to the possible occurrence of Alzheimer’s, ten years later.

Thinning of the cerebral cortex has been associated with mild Alzheimer’s disease, so Harvard researchers used magnetic resonance imaging (MRI) to assess cortical thickness in two samples of adults who were ‘cognitively normal’.  The first sample had 33 subjects, who were followed subsequently for an average of 11 years; the second sample had 32 subjects, who were followed for an average of 7.1 years. In the first sample 8, and in the second 7 subjects developed Alzheimer’s disease during follow-up.

All the participants were classified into one of 3 groups, based on their cerebral cortex thickness:

1. High thickness – 9 individuals, none developed Alzheimer’s.
2. Average thickness – 45 individuals, 20% went on to develop Alzheimer’s.     
3. Low thickness – 11 individuals, 55% went on to develop Alzheimer’s.

The actual difference in thickness between groups 2 and 3 was quite similar, about 0.2 mm.  However, this subtle difference was considered reliable enough to detect a degree of atrophy in people without symptoms but who would develop dementia within 10 years or so.  The researchers conclude that evidence of cortical thinning obtained by MRI is a “potentially important imaging biomarker of early neurodegeneration”. 

The UK Alzheimer Society are somewhat critical of this study and its conclusions, commenting on the small sample size and the inability to say for certain which people will go on to develop Alzheimer’s.  Nevertheless, it’s important to recognize that a detectable change in half the subjects examined was associated with the development of dementia within 10 years.  But, as with genetic testing, it’s probably a question of: “Do I really want to know that?” – at least until an effective treatment is available . . .