290 NEUROBIOLOGY OF AGING, VOLUME i 1, 1990 ABSTRACTS OF SECOND INTERNATIONAL CONFERENCE ON ALZHEIMER'S DISEASE

RISK FACTORS & EPIDEMIOLOGY

interrater agreement. Moreover special methodologies for population sampling in developing countries will be identified. During the pilot study research instruments and diagnostic procedures will be validated in each participating country. The field study is arranged into two times. During time one the prevalent cases of dementia will be identified. During time two re-assessment of the same population sample will allow us to obtain the incident cases and the relative risk values. Both in time one and in time two, case finding will be based on a multi-phase procedure, including a screening phase followed by an extensive clinical and paraolinical assessment of subjects to diagnose dementia and dementia subtypes.

152

PILOT STUDIES IN THE N.A.S. REGISTRY SUGGEST 60% CON- CORDANCE FOR ALZI'IEIMER'S DISEASE IN M.Z. TWIN PAIRS. *J. C. S. Breitner, K. A. Welsh, IC M. Mngruder-Habib, C. M. Churchill, C. D. Robinette, M. F. Fotstein, J. Brandt.

Twin studies can provide information about both genetic and environ- mental causes of Alzheimer's disease (AD), but large numbers of twin pairs are needed for meaningful results. The N.A.S. registry of aging twin veterans contains 9,000 living pairs of white male twins born between 1917 and 1927. In preparation for a major study of AD using this resource, we undertook pilot work by attempting to contact the 442 pairs (884 subjects) listed as residing in the Carolinas, Virginia, DC or Maryland. Fifty-five subjects were deceased; 678 (82%) of the remainder responded. Ascer- tainment methods included a brief telephone interview for cognitive symptoms, telephone history interviews with spouses or other informants, and in-person examination of screen-positive subjects; Eighteen (2.6%) of the respondents screened positive for possible dementia and were asked to participate in a formal clinical assessment. Six subjects refused; one died before his condition could be evaluated, so that he and his brother (also screen-positive) could not be included in the analyses. One of the 10 remaining screen-positive probands had cerebrovascular disease with depression. One monozygotic (MZ) pair of screen-positive subjects was concordant for Probable AD (NINCDS criteria). Remaining probands had Possible AD or a "mild/ambiguous" cognitive disorder suggesting early AD. All of their screen-negative co-twins were examined in person: 2 of 4 MZ co-twins showed symptoms suggesting early AD, but none of 3 DZ co-twius showed any abnormality. The results of this work suggest: 1) that systematic ascertainment of AD in the N.A.S. registry by the above methods is feasible; 2) that the prevalence of progressive cognitive disorder in the registry is about 2%; 3) that concordance for presumptive AD in MZ pairs (60% now, but possibly more if other co-twins have later onsets) exceeds prior estimates; but 4) that such rates of concordance may become apparent only upon detailed evaluation of apparently normal co-twins as well their impaired brothers.

Supported by the Alzheimer's Association, the Sandoz Foundation for Gerontologic Research and NIH grant AG07922. C.M. Owens, S.S. Left and'E.J. Friedrich provided superb technical assistance.

153

UNIFYING MODEL FOR RISK FACTORS IN ALZHEIMER DISEASE *L.F. JARVIK, M.D., Ph.D., WLA VAMC, Brentwood, and UCLA/NPI Los Angeles, CA 9007:3, USA.

Risk factors for Alzheimer Disease exhibit nearly unequalled diversi ty. They range from largely accepted ones (such as age, FAD, Down Syndrome, Parkinson disease, and perhaps head in jury) to more controversial ones, (including viruses, aluminum toxic i ty, nutr iUon, neuronal endowment, metabolic disturbance, impaired host defense, surgical trauma, as well as educational, intellectual, and sensory deprivation). Yet, i t is possible to accomodate all or the putative r isk factors wi th in a single theoretical framework. A model wi l l be presented.

154 POPULATION BASED STUDTES OF ALTJMINZUM IN ALZIW.IMER'S DISEASE *C. M~TYN, T. NOt]EL.MID, C. OSMOND. MRC Env i ronmen ta l Ep idemlo logy U n i t , U n i v e r s i t y o f Southampton, Southampton, England.

if aluminJum is a causal factor in the development of Alzheime~" disease, people exposed to large amounts of bioavailable alum~nium will be at higher risk than people exposed to

small amounts. This straightforward predictioi~ can be tested by epidemiological techniques.

In a survey of 88 districts within England and Wales, the

incidence of Alzheimer's disease, other causes of dementia and late onset epilepsy was estimated from the records of neuro-diagnostic centres. Details of aluminium concentrations

for all important water sources supplying these districts were made available by the local water authorities. There was a

positive relation between rates of Alzheimer's disease and water aluminium concentrations. The mean rate of Alzheimer's disease in districts where the aluminium

concentration exceeded0.11 mg/l was 1.5 times higher than the rate in districts where aluminium concentrations were

below the limit of detection. This positive relation was not found for other causes of dementia or for late-onset

epilepsy.

Correlation does not necessarily imply cause; the association

that we observed may have been due to the operation of some

unknown confounding variable. Case-control studies to examine

the relation between aluminium and Alzheimer's disease in individuals, rather than in populations, and to investigate other environmental sources of aluminium are in progress.

155

PREVALENCE OF DEMENTIA AND PROBABLE ALZHEIblER'S DISEASE IN THE FRAMINGHAM STUDY. *J.E. Knoefel , D.L. Bachman, R.T. Llnn, P.A.Wolf, L.R. White, R.B. D'Agosttno. Department of Neurology, Boston University School of Mediclne, Boston, MA 02118; Veterans Administration Medical Center, Boston, MA 02130; and National Institute on Aging, Bethesda, MD 20892

A longitudinal study of dementia in the Framlngham Study was begun tn 1982 with a cohort of 2341 subjects determined to be free of dementia at initial screening. Having participated tn the Framlngham Study since 1950, the subjects were 62 to 94 years of age with 61% being women. Subjects were screened with the Mint-}4ental State Examination every two years; age- and education-adjusted scores designated approximately 15% of subjects for in-depth evaluation each screening period.

The detailed evaluation for dementia included a history and examination by a neurologist, and a battery of standardized neurospychologtcal tests. Results of the evaluations, all FramlnRham Study records and individual medical records were reviewed by a three-member dementia review board and a determination as to the presence on absence of dementia was made. If present, the dementia was also classified as to type by the dementia review board. Subjects determined by the board to be free of dementia were evaluated again in the next biannual cycle.

The present report confirms a dramatic increase in prevalence of dementia with increasing age. In age groups from 61 to 85+, the prevalence steadily increased from 3.5/1000 to 225/1000 with an average of 36.7 for all subjects 61 years of age and older. Women had more than twice the prevalence rate of men in the 85+ year age group.

Alzheimer's Disease prevalence rates also showed a dramatic rise with Increasing age. The rate for subjects less than 64 years of age was nil to 125/1000 aged 85+ years. Prevalence was 20.6/1000 for all subjects. On average, the prevalence of Alzheimer's Disease in women was 2.5 t imes that of men and accounted for 56% of all dementia in this study.

The Framingham Study represents a ~eneral community-based population examined over a number of years. Diagnosis of dementia and Alzheimer's Disease was made with longitudinal follow-up Of the~e subjects. Hence, dementia and Alzhetmer's Disease prevalence rates from this study may well reflect an accurate picture of the prevalence of these disease conditions In the general United States population.

156

THE PREVALENCE OF DEMENTIA IN EUROPE: A COLLABORATIVE STUDY OF 1980-1990 FINDINGS. *M.M.B. Breteler, W.A. Rocca, L.A. Amaducci, A. Hofman, for the E U R O D E M Prevalence Research Group. Dept. Epidemiology & Biostatistics, Erasmus University, Rotterdam, The Netherlands, and SMID Center, Florence, Italy.

To obtain age- and gender-specific estimates of the prevalence of total dementia in Europe, and to study determinants of differences in