Dementia as a major public health concern : intelligence testing revisited
In 1976 it was proposed that senile dementia, a potential affliction of old age, be redefined as Alzheimer's disease, a rare diagnosis previously assigned to presenile dementia occurring in middle life. In response to a "public culture" generated by those caring for the afflicted, together with leaders of the biomedical reserch community, substantial financing has been allocated by the U.S. Congress to the National Institutes of Health, for investigation of senile dementia redefined as a "dread disease". This has funded studies in the neurosciences, and a range of epidemiological and high technology diagnostic investigations for which psychiatry developed a "case-finding" method. The "cognitive paradigm" for dementia was conceived by American psychiatry within a now dominant "biological" model which imputes physical causation to mental disorders and stresses "objectivity" in diagnosis. This has legitimated the use of "mental test" instruments based upon, or validated against, "intelligence tests" developed by psychologists for quantification of "intelligence" now redefined as "cognition". In a study funded by the National Institute of Mental Health, three cognitive assessment instruments were administered to a sample of individuals aged 60-93 with a broad range of educational experience across the age spectrum. Education rather than age was found to be the most significant predictor of test results for each instrument, and when the tests were repeated a marked "learning effect" was detected among those with the least education and lowest baseline scores. However, the identification of low education as a predictor, albeit less powerful than age for "cognitive impairment" indicative of dementia in other investigations has now been interpreted as a "risk factor" rather than a confounding variable and now enters into genetic mental testing models. Negative stereotyping of "old age", strongly associated with images of "senility", and "burden of ageing" economic arguments have therefore been reinforced by the dissemination of prevalence estimates from epidemiological studies conducted in communities in which there is an inverse correlation between age and education. In the meantime, basic scientists have failed to discriminate precisely between neuropathological changes indicative of "disease" and those of "normal ageing" or to establish a functional link between such changes and dementia behaviour in vivo. In consequence the legitimating rationale for public financing of the "Alzheimer's enterprise", i.e. "clinical benefit" remains elusive.