RespiteMatch.com Health Blog

BODY PARTS
By Justine Ferrari
01oct05

THERE are few signals of the creeping advance of Alzheimer’s disease. Before you know it, the occasional lapses of memory have overtaken family members and your parent is wandering the streets and presenting you with a bouquet of flowers containing a set of dentures.

As with any disease, catching it early is half the battle. But you can’t do a blood test to detect Alzheimer’s disease, and in fact a positive diagnosis can only be made after death with a brain autopsy. But a recent study has identified a way for doctors to identify the disease in its early days.
A study for the National Institute on Ageing in the US has found for the first time that a drop in weight among the elderly can predict the onset of Alzheimer’s disease.

The study by the University Medical Centre in Chicago, published in the journal Neurology (2005;65:892), tracked the body mass index of more than 800 people aged 65 years or older for more than six years. BMI is a measure of your weight adjusted for your height, which is used to determine if you are overweight for your size. Those studied had an average BMI of 27.4 when they started, which is deemed overweight, and one in five developed Alzheimer’s disease over the period of the study.

The researchers found that losing about one unit of BMI a year increased the risk of Alzheimer’s by 35 per cent. Those whose BMI remained stable were still 20 per cent more likely to develop it than those who gained weight of about 0.6 of a unit of BMI a year.

Doctors know that people with Alzheimer’s tend to lose weight once they have the disease, but this is the first time the relationship has been shown before the onset of the disease.

Alzheimer’s disease is the most common, but not the only, form of dementia. A recent government report says about one in four Australians over the age of 85 years shows symptoms of dementia, which numbers about 200,000 people. Alzheimer’s accounts for more than one in two cases of dementia.

The first sign is usually forgetfulness. As seen in the film Iris, on writer Iris Murdoch, sufferers become disorientated and unable to perform everyday tasks. Often people with Alzheimer’s will undergo a personality change and their intellectual capacity diminishes.

In Alzheimer’s disease, brain cells or neurons die, with sufferers losing as much as 20 per cent of their brain volume.

The dead neurons leave large empty spaces between the grey matter and accumulations of proteins that clump in and around the neurons. A protein called beta amyloid clumps together with degenerating bits of neurons and other cells to form amyloid plaques in the tissue between the nerve cells.

Within the neurons, a protein called tau forms bundles of twisted filaments, known as tangles. In a healthy neuron, the tau protein is involved in the communication between nerves, helping to deliver substances through microtubules in the nerve cells. But in Alzheimer’s, the tau is changed and twists, causing the microtubules to disintegrate.

The main areas of the brain affected in Alzheimer’s disease are the temporal, parietal and frontal lobes, which are the areas associated with memory and intellectual capacity. The NIA study suggests that one area of the brain also affected is that which controls weight, and so results in the declining BMI before the intellectual and cognitive declined is noticeable.