Mortality from dementias and neurodegenerative disorders in people aged 15-64 in England and Wales in 1979-96.

There is now good evidence that the new variant of Creutzfeldt-Jakob disease first identified in 1996 is caused by exposure to bovine spongiform encephalopathy (BSE). Because Creutzfeldt-Jakob disease can be difficult to diagnose, it is possible that cases of sporadic and new variant Creutzfeldt-Jakob disease have occurred that were not correctly diagnosed because postmortem or neuropathological examinations were not performed. In such cases patients could have been certified as dying from another dementia or a neurodegenerative disease. If this had occurred, mortality from Creutzfeldt-Jakob disease would have been underestimated, with a corresponding increase in mortality from other dementias and neurodegenerative disorders. We investigated whether there had been any increase in mortality from dementias and neurodegenerative disorders since 1979.