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Health Evidence Bulletins - Wales

Literature searches completed on: 19th April 1999

8: Dementia in Down Syndrome

This bulletin is a supplement to, not a substitute for, professional skills and experience. Users are advised to consult the supporting evidence for a consideration of all the implications of a recommendation.

The Statements The Evidence
8.1 Background
8.1a. The quoted prevalences of dementia in people with Down syndrome are: 0-4% under 30 years of age; 2-33% for 30-39 years of age; 8-55% for 40-49 years of age; 20-55% for 50-59 years of age; 29-75% for 60-69 years of agei. Zigman W, Schupf N, Haveman M, et al. The epidemiology of Alzheimer disease in mental retardation: results and recommendations from an international conference Journal of Intellectual Disability Research. 1997; 41(1): 76-80
(Type V evidence – expert review of 14 studies)
8.1b. Between 31% and 78.5% of adults 65 years or older with intellectual disability but without Down syndrome show Alzheimer’s neuropathologyi,ii,iii. i. Barcikowska M, Silverman W, Zigman W, et al. Alzheimer-type neuropathology and clinical symptoms of dementia in mentally retarded people without Down syndrome. American Journal of Mental Retardation 1989; 93(5): 551-7
(Type IV evidence - post-mortem findings of 70 people aged over 65, with intellectual disability but without Down syndrome)
ii. Cole G, Neal JW, Fraser WI, Cowie VA. Autopsy findings in patients with mental handicap. Journal of Intellectual Disability Research 1994; 38: 9-26
(Type IV evidence – observational autopsy study of people with intellectual disability – 15 Down syndrome and 18 non-Down syndrome)
iii. Popovich ER, Wisniewski HM, Barcikowska M et al. Alzheimer neuropathology in non-Down’s syndrome mentally retarded adults. Acta Neuropathologica 1990; 80: 362-367
(Type IV evidence – observational autopsy study of 385 non-Down syndrome people with intellectual disability)
8.1c. Almost all adults over the age of 40 years with Down syndrome display Alzheimer’s neuropathologyi. i. Mann DMA. Alzheimer’s disease and Down’s syndrome. Histopathology 1988; 13: 125-137
(Type IV evidence – review of case-reports including 398 cases altogether)

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8.1d. Among people with intellectual disability, the only known risk factors for the development of Alzheimer’s disease are increasing age and Down syndromei,ii.
It is not clear what effect, if any, possible risk factors as seen in the general population – family history, low educational level, head trauma, cardio-vascular disease, stroke, diabetes, apolipoprotein E-4, major depressive episode – have on dementia in people with Down syndromei,ii,iii,iv.
i. Zigman W, Schupf N, Haveman M, et al. The epidemiology of Alzheimer disease in mental retardation: results and recommendations from an international conference. Journal of Intellectual Disability Research 1997; 41(1): 76-80
(Type V evidence – expert review of 14 studies)
ii. Tsolaki M, Fountoulakis K, Chantzi E, et al. Risk factors for clinically diagnosed Alzheimer's disease: a case-control study of a Greek population. International Psychogeriatrics 1997; 9(3): 327-41
(Type III evidence - case-control study of 65 patients with Alzheimer’s disease and 69 age-matched controls)
iii. Deb S, Braganza J, Norton N et al. Apoliprotein E e4 allele influences the manifestation of Alzheimer’s disease in adults with Down’s syndrome. British Journal of Psychiatry 2000; 176: 468-472
(Type IV evidence – case-control study of the ApoE genotypes among 24 adults with dementia and 33 non-demented adults with Down syndrome, aged 35 or over, and an additional group of 164 non-intellectually disabled adults. Also a meta-analysis of 9 studies)
iv. Rubinsztein DC, Hon J, Stevens F et al. ApoE genotypes and risk of dementia in Down syndrome. American Journal of Medical Genetics 1999; 88(14): 344-347
(Type IV evidence – case-control study of the ApoE genotypes among 20 demented and 25 non-demented adults with Down syndrome. Also a meta-analysis of 6 studies)
8.2 Assessment

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8.2a. The diagnosis of dementia in people with intellectual disability, especially in the early stages, is made difficult by the lack of reliable and standardised criteria and diagnostic procedures.
Neuropsychological testsi and informant-based questionnaires such as the Dementia Questionnaire for Persons with Mental Retardationii need further evaluation before they could be accepted for day-to-day clinical assessmentiii.
(Health gain notation – 4 "unknown")
i. Aylward EH, Burt DB, Thorpe LU, Lai F, Dalton A. Diagnosis of dementia in individuals with intellectual disability. Journal of Intellectual Disability Research 1997; 41(2): 152-64
(Type V evidence – expert opinion based on a review of observational studies)
ii. Evenhuis HM. Further evaluation of the Dementia Questionnaire for Persons with Mental Retardation (DMR). Journal of Intellectual Disability Research 1996; 40(4): 369-73
(Type IV evidence – 5 year longitudinal follow-up of 33 elderly institutionalised persons (aged 70 and over) and 45 institutionalised persons with Down syndrome (aged 35 and over) with no dementia in the diagnosis at initial evaluation)
iii. Deb S, Braganza J. Comparison of rating scales for the diagnosis of dementia in adults with Down’s syndrome. Journal of Intellectual Disability Research 1999; 43(5): 400-7
(Type IV evidence – a study of the Clinician’s diagnosis (ICD-10), the Dementia Questionnaire for Persons with Mental Retardation (DMR), the Dementia Scale for Down Syndrome (DSDS) and the Mini Mental State Examination (MMSE) in 62 adults with Down syndrome – 26 demented and 36 non-demented according to clinician’s diagnosis)

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Health Evidence Bulletins: Wales, Duthie Library, UWCM, Cardiff CF14 4XN. e-mail: weightmanal@cardiff.ac.uk