Last year it was also reported that autopsies of two young boxers who died in the ring revealed tangles, but not plaques, in their brains. Other forms of head injury have been shown to lead to plaque formation within days. It is not known whether the effects of such traumas would have led to Alzheimer's Disease. It is evident however that, in some instances, there can be a rapid development of plaques and tangles in the brain, in contrast to the very slow buildup in Alzheimer's Disease. A second risk factor is being female, although this factor could well become less important in the future with the increasing use of post-menopausal estrogen replacement therapy since there is some evidence that estrogen may delay the onset of the disease.
Genetic factors can also play a role.
Having a close relative with Alzheimer's Disease increases the risk. This is especially true for identical twins where the unaffected twin has an even chance of developing the disease. In the case of first degree relatives, that is parents, children or siblings, the risk is considerably reduced but nevertheless is present. One study has shown that a person aged eighty with no parent who had Alzheimer's Disease has about a one in ten chance of being afflicted. This risk increased to one in three if one parent had the disease and to one in two if both were affected.