Education and the prevalence of dementia and Alzheimer's disease

Alzheimer’s disease (AD) is a democratic process. Physicians and psychologists, chess masters and physicists, mathematicians and musicians may become victims of this disorder. A poignant example that reached the national press was the obituary of George Beadle, a pioneer of biochemical genetics (whose experiments with mutations in the mold Neurospora crassa established the “one gene, one enzyme” relationship), a Nobel Laureate and later President of the University of Chicago, who died in 1989 of A D . I Yet a number of recent community studies report that individuals with lack of education or low education are more likely to develop dementia and AD. This finding has profound social and biological as well as medical implications. The effect of no or low education on the prevalence of dementia confirms the 1988 prediction of Mortimer2 that education would provide protection against dementia. He s ta ted (page 39) t h a t “psychosocial factors act primarily to reduce the margin of intellectual reserve to a level where a more modest level of brain pathology results in a d i a g no s a b 1 e dementia. ” He h y p o t h e s i ze d tha t “psychosocial risk factors will have their strongest associations in late-onset DAT of mild to moderate severity and . that low premorbid intelligence hastens the clinical diagnosis of DAT. ” During the past 3 years the results of several epidemiologic studies have in part confirmed these predictions. Moreover, the recent finding that a close relationship exists between neocortical synaptic density and cognitive decline in AD provides a biological stratum for the postulated “intellectual reserve. ” Our attention was focused on this risk factor by a population survey of dementia carried out in Shanghai in 1987.394 This was a two-stage survey of 5,055 subjects over age 55, stratified so that about one-third were 55 to 64, one-third 65 to 75, and one-third over the age of 75. The diagnosis of dementia was made after detailed clinical evaluation and was based on criteria in the third edition of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (DSM-III). 5 Two-thirds of those diagnosed as demented met the clinical requirements of the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) and the Alzheimer’s Disease and Related Disorders Association (ADRDA) criteria for AD.6 An unexpected finding in the Shanghai survey was that lack of education is a major risk factor for and a major determinant of the prevalence of dementia.7 The Shanghai elderly differ from those in the United States in that 26.7% of the sample had never been to school and were not only illiterate but many could not carry out such presumably simple tasks as copying the overlapping pentagon figure of t he Mini-Mental S t a t e Examination (MMSE ),8 having had no childhood experience with a pen, pencil, o r brush.3 Another 36.7% had received 1 to 6 years of elementary education, many only 1 t o 2 years; and 36.1% had middle school or greater (some with doctoral degrees), a very wide spread in the educational spectrum. In subjects over the age of 75, there was a striking increase in the prevalence of clinically diagnosed dementia in those with no or low education. Adjusting for age in a multivariate analysis, the relative risk of developing dementia was approximately twice for those with no education as compared with those who had attended middle school and for those with elementary school education. Similar results have been obtained in subsequent surveys of dementia in southwestern F r a n ~ e , ~ Appignano, Italy,loJ1 Stockholm, Sweden,12 Finland,13 and Ashkelon, 1~rae l . l~