BACKGROUND AND METHOD We related geographical variation of 'probable' presenile Alzheimer's disease (AD PSD) to exposures to possible risk factors for AD PSD and vascular dementia (VaD) and to geographical differences in survival times after presentation with AD PSD.
RESULTS We found that an ecological measure of socio-economic deprivation was related to VaD but not to AD PSD. Among men with AD PSD and VaD, specific occupations conveyed no altered risk but having fathers who were coal miners was associated with AD PSD and VaD in offspring. Increased paternal age was associated with AD PSD but only in men. These factors acted independently of one another and did not distinguish between geographical areas of high and low incidence.
CONCLUSIONS The length of survival after presentation with AD PSD distinguished between these areas, and when migration between these areas was taken into account, a plausible multifactorial model of the harmful effects of environment emerged, which acted independently of risk factors acting earlier in life.