Alzheimer's disease in 22 twin pairs 13-year follow-up: Hormonal, infectious and traumatic factors

We obtained follow-up data on 22 sets of twins where at least one twin had Alzheimer's disease (AD), The concordance rate for monozygotic twins (n = 1 7 pairs) was 59%, whereas that for dizygotic twins was 40%. In our series 8 monozygotic twins had hysterectomies; all had AD. The twins with hysterect omies also had a tendency to develop AD at an earlier age than their co-twi n, Five twins with serious systemic infection developed AD, and they tended to have earlier onset than their corresponding twin, We found no strong ev idence that head injury predisposed to AD.