Dementia and Alzheimer's Disease

From near-obscurity only a generation ago, Alzheimer's disease is now probably, after cancer, the most feared disease of old age.

Alzheimer's has been chillingly described as an affliction whose victims suffer the loss of qualities that define human existence.

Once considered a rare disorder, it is now known to be the most common type of senile dementia, defined as physical damage to the brain in old age that results in major changes to reasoning, memory, personality and behavior.

Until recently, the only way to distinguish Alzheimer's from other types of dementia was by post-mortem examination of the brain. A typical AD brain is found to be partly atrophied; with the brain cells clumped together in what are called 'neurofibrillary tangles' or 'plaques'.

The second major type of dementia is vascular dementia, where the interruption of the brain's blood supply, usually due to 'mini-strokes', causes brain cells to die.

These two main types of dementia can now sometimes be distinguished from each other by brain scans using either magnetic resonance imaging (MRI) or positron-emission tomography (PET).

Senile dementia is not as inevitable as many people might imagine: between 25 and 50 per cent of individuals over 85 are spared it. Nevertheless, dementia is on the increase, so the drug companies claim, because of the simple fact that we're all living longer. It is believed to be incurable.