alzheimer's disease is the commonest form of dementia afflicting millions across the world. Patients with the disease slowly loose all powers of thought and are eventually reduced to vegetables completely dependant on others for their survival. A lot of research has gone to find a cure or, at least, a preventive treatment.

Now, German researchers at the Technical University of Munich say that children born to older fathers have a higher risk of succumbing to Alzheimer's. Older mothers are more likely to give birth to babies with Down's syndrome, and people with Down's are more susceptible to Alzheimer's disease. Intrigued by the association between these two mental disorders, Lars Bertram and his colleagues wondered if parental age plays any direct role in Alzheimer's.

The researchers studied 206 Alzheimer's patients. Susceptibility to the disease is linked to certain major genes, so the first step was to try to establish each patient's inherited risk. To do this, Bertram and his team found out the incidence of Alzheimer's in each patient's family.

Then they examined groups of patients at each extreme