REVIEW Afr J 2011;14:194-199 in : a review of diagnostic challenges

M Nagdee 1,2 1Fort England Hospital, Grahamstown, Eastern Cape, South Africa 2Department of Psychiatry, Walter Sisulu University, Eastern Cape, South Africa

Abstract The evaluation of dementia in individuals with intellectual disability (ID), which will guide subsequent intervention, care and management depends on the systematic review of a number of factors: (1) the individual historical context, obtained from multiple sources, (2) evaluation of the pre-existing cognitive, behavioural, psychiatric, medical and adaptive skill profile, (3) the constellation, and pattern of evolution, of presenting , (4) results of focused investigations, and (5) refinement of the differential diagnosis. In patients with ID, standard clinical methods need to be supplemented by careful, longitudinal behavioural observations, and individually tailored assessment techniques. Co-morbidity, multiple biological, psychological and socio- environmental factors, and complex interactions among events, are the reality for many ageing people with ID. Determining the various influences is often a formidable clinical task, but should be systematically carried out using medical, cognitive, behavioural, neuropsychiatric and psycho-social frameworks.

Key words: Dementia; Intellectual disability; Mental retardation

Received: 23-05-2010 Accepted: 09-07-2010 doi: http://dx.doi.org/10.4314/ajpsy.v14i3.1

Introduction Epidemiology People with intellectual disability (ID) [this term is used in Dementia can occur at any age, but is largely a disorder of preference to mental retardation (MR)] are prone to later life. The prevalence of dementia in the general developing dementia in later life. This is particularly population rises markedly with increasing age: from 1-2% in important in the context of rising life expectancies in this people aged 65-69 years, to 16-25% in those over 80 years. 3 population. The average life expectancy of with ID (in Among people with ID, dementia is liable to strike more often, developed countries) is 66 years and increasing. 1,2 As these and earlier. A number of community-based studies of ID individuals age, they present with increased rates of physical, populations have yielded age-matched prevalence rates of sensory and cognitive impairments. This results in increasing about 14% in people over 59 years, and 22% in those 65 years health and social care needs, with resultant pressures on and over. 4 The comparative rates among same-age adults carers and support services. Clinicians can expect to come with Down are much higher, reaching over 40% in across increasing numbers of people with ID who develop those over 50 years, and over 70% for ages above 60 years. 5 dementia as they grow older. Whilst resource priorities in developing countries may be focused elsewhere, Diagnostic criteria people with ID still form a significant, and particularly The diagnosis of dementia in people with ID presents a vulnerable, proportion of our patient population, and have number of challenges 6: been historically neglected in many respects. As • Assessment techniques and tools in common clinical use identification, evaluation, diagnosis, and management of such for the non-disabled population may not be appropriate, patients can be challenging, familiarity with the key issues is especially for individuals with more severe pre-existing essential for all involved in their care. levels of intellectual impairment. Diagnosis in the ID population requires a change in status from baseline functioning, not a change from a “normal” level. 7 Correspondence • Pre-existing cognitive impairments and disturbances in Prof. M Nagdee Fort England Hospital, P/Bag X1002, Grahamstown, Eastern Cape, behaviour, personality and emotional control may conceal South Africa the often subtle and insidious emergent symptoms of email: [email protected] dementia. 8,9

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• Some signs of dementia (such as dysphasia, dyspraxia deteriorating course, leading to delays in diagnosis and and agnosia) are often difficult to recognize in people treatment. with ID, particularly in the early stages of the illness. • People with ID have a predisposition to co-morbidity, These criteria have therefore been excluded from which is often severe or frequent enough to influence some ID diagnostic schemes. 10,11 the evaluation and interpretation of their cognitive • Changes in repertoire of adaptive skills or behaviours impairment. may predate any demonstrable early memory • The effects of chronic medication on cognitive function impairments in ID patients. are often overlooked in clinical practice (especially the • The perception, manifestation and degree of functional use of multiple agents). impairment caused by the dementia syndrome largely • There is often a lack of consistent and reliable depends on pre-morbid , level of and documentation of prior cognitive and adaptive skill training, individual life circumstances, and individual levels, making it difficult to detect decrements until they ability to compensate for newly acquired deficits. 7 become pronounced. • To be indicative of dementia, any changes over time must be greater than those related to normal aging in A comprehensive and focused history from both the patient adults with ID. 7 and multiple informants/sources (e.g. members, • Neither the ICD-10 nor the DSM IV-TR diagnostic carers, medical records) is usually the most valuable criteria for dementia make any specific mention of diagnostic tool for dementia in ID. The information- ID/MR. gathering exercise aims to: (1) systematically document details of symptoms and functionality, (2) identify treatable To date, there is a lack of consensus on a standardized causes of dementia, and aid in clarifying a working approach to the diagnosis of dementia in ID. As a step differential diagnosis, and (3) conceptualise the current towards such standardization, diagnostic criteria have been problems within a broader pre-morbid and psychosocial proposed by the Working Group for the Establishment of setting, in order to guide appropriate and effective Criteria for the Diagnosis of Dementia in Individuals with management. It is imperative to obtain collateral Intellectual Disability [under the auspices of the information from people who are familiar with the International Association for the Scientific Study of individual’s past behaviour and level of functioning, as well Intellectual Disability (IASSID) and the American as her/his present performance. A clear history of Association on Mental Retardation (AAMR)]. 10 These are declining function may be difficult to elicit in people with largely based on ICD-10 diagnostic criteria (with its more severe ID, where levels of ability may be significantly relatively heavier emphasis on non-cognitive changes in impaired in the first place, or where impairments in dementia). These authors strongly recommend that may mask early evidence of decline. dementia should only be diagnosed when longitudinal data Specific enquiry about the presence of risk factors (e.g. demonstrate clinically significant declines in functioning. If family history of dementia, a previous , or some, but not all, of the criteria are met, a diagnosis of vascular morbidity) is equally important. A family history of “possible dementia” is appropriate. This group has further dementia, ID, and neuropsychiatric problems requires proposed a working battery of tests (for both informants special attention. The history should pay particular and patients) for the diagnosis of dementia in adults with attention to previous diagnoses and treatments, especially ID. 8,10 As in the general population, diagnostic certainty will the use of medication. Careful attention should also be paid be enhanced if decline is observed on many tests and to the timing of onset, pattern and progression of across longitudinal assessments. symptoms. Symptoms often have a subtle and insidious evolution (a fact usually more easily appreciated by Clinical features patients and carers retrospectively). Symptoms may, The clinical presentation of dementia among adults with ID however, present abruptly, especially in with (at most levels of disability) is similar to that of adults in the potentially treatable aetiologies. There may be identifiable general population. Nonetheless, there are a number of precipitating factors e.g. a relatively minor physical illness, factors that impact on the clinical evaluation of dementia in a change in environment or following bereavement. The the context of ID 6,12,13,14 , including: history should screen for the presence of pre-existing or • The lack of consensus on what constitutes normal age- co-morbid medical conditions (and their respective related decline in people with ID, and how to treatments). Physical symptoms and signs may also be due distinguish this from dementia. to adverse effects of medication. It is well recognized that • The lower the pre-existing intellectual and adaptive people with ID have a significant predisposition to sensory level of functioning, the more difficult it becomes to impairments, especially hearing and visual impairments evaluate change and document progression. that can be mistaken for, aggravate, be co-morbid with, or • Pre-existing cognitive and psycho-social deficits may mask an underling dementia. 15,16 mask signs of deterioration. • Early signs of dementia (cognitive, neuropsychiatric or Cognitive changes adaptive skills decline) are often subtle and difficult to The core symptoms of dementia in people with ID are of detect. multiple, and usually progressive, deficits in a number of • There is a bias amongst many health professionals and areas of cognitive function, similar to those in the general carers towards aging people with ID in expecting a population. A history of memory impairment is often the

African Journal of Psychiatry • July 2011 195 REVIEW Afr J Psychiatry 2011;14:194-199 earliest and most prominent feature (particularly with the inappropriately minute or irrelevant detail, or perseveration. cortical dementia , e.g. Alzheimer’s ). Language dysfunction may present as more specific deficits, Early changes may be subtle or intermittent, with non- such as receptive or expressive dysphasia. In the later stages specific complaints of forgetfulness, absent mindedness, of illness, speech becomes increasingly disorganized, difficulty concentrating or general mental fatigue, leading to progressing to incoherence or muteness. In those with poorer difficulty with novel or more complex tasks, progressing to pre-existing verbal skills, evidence of language impairment more mundane, everyday tasks. Memory decline most will range from subtle, barely perceptible changes or commonly manifests as impairment of recent memory and a decreases in the use of language to total loss of verbal reduced capacity for new learning. This is often noticed by expression. 7 The pre-existence of communicative others first, but it is usually difficult to date the onset with impairments makes it more likely that dementia will be well accuracy. There may be difficulty remembering events of advanced before it is clinically recognized. 9 As with many the day, recently held conversations, or the names of other symptoms and signs, it is the change from pre-morbid acquaintances. Patients may have word finding problems, patterns and levels that is the crucial factor. forget the location of everyday items, or perhaps require A range of other cognitive impairments may be present. more prompting than usual to complete everyday tasks. There may be evidence of varying degrees of dyspraxia, They may have difficulty remembering the steps required typically presenting as difficulties with grooming, dressing, to perform previously mastered tasks, or following self-feeding, cooking or similar everyday motor tasks. Various direction. Carers may report that information needs to be agnosia's may occur e.g. in the visual (e.g. prosopagnosia) or presented more slowly, or in a more simplified format, and tactile (e.g. astereognosis) sensory modalities. For individuals patients may require more frequent reminding. Eventually, with moderate to severe levels of ID, dyspraxia’s and memory impairment may become severe, with only the agnosia’s may be the first deficits to be apparent. Agraphia, earliest or most remote information remembered. This may alexia and acalculia may be diagnosed in those with prior present as perseveration on the distant past, and may requisite skills in these areas. 7 There is also usually a history progress to become quasi-delusional, where the person of impairment in complex (e.g. executive function) experiences the present as if it is the past. Intellectually and motivational behaviour. Even mild executive dysfunction disabled individuals are particularly vulnerable to such may significantly impair the capacity to fulfil (e.g. memory impairments, as previously limited adaptive skills providing adequate self-care), perform everyday tasks (e.g. and coping strategies undergo even further decline. preparing a meal, or handling money), interacting with others Patients may become even less able to communicate in a socially acceptable manner, or regulating emotions and effectively e.g. to explain personal concerns and needs to behaviour appropriately. Such changes in complex cognitive others, or to socialize and interact adequately. Peers, function are, relative to pre-morbid levels, and may be more acquaintances and carers may feel socially unsatisfied, or difficult to recognize in people with more moderate or severe estranged, with regards to the person developing dementia. levels of ID. 7 Patients with a higher baseline of intellectual Patients themselves often grow increasingly frustrated, functioning may appear to lose more cognitive skills over irritable, confused or depressed by the changing time. 17 The pattern, rate and degree of decline, however, are circumstances. highly variable from one individual to another, and are not Orientation also becomes progressively more impaired, easily predictable and may be more salient than other cognitive deficits. Disorientation for time is usually an early feature, and often Behavioural and psychiatric presentation presents as difficulty in temporal sequencing. This may Changes in behaviour and psychiatric symptoms are upset personal, family, social or institutional routines e.g. common in ID patients with dementia. The Working Group of arriving late for meals or missing social engagements. the International Association for the Scientific Study of Spatial disorientation is also common, with people having Intellectual (IASSID) recommends greater difficulty getting around the home (e.g. returning to the emphasis be placed on behavioural and personality changes bedroom from the bathroom) or the neighbourhood (e.g. (together with evidence of functional decline) in the getting lost whilst returning from the local shop). This can diagnostic evaluation. 7,18,19,20 Behavioural changes present in a be a particular problem in unfamiliar environments or variety of ways, ranging from patterns of excitement, following unexpected changes in routine. Spatial escalation and disinhibition, to slowing and apathy. They are disorientation may impact on everyday skills (e.g. placing also of variable severity, often being subtle at first and then the body in an appropriate position at the table for meals), progressing in tandem with progression of the underlying requiring increasing levels of support from carers. Visual dementia. Restlessness, impulsivity and agitation are and hearing impairments, which occur frequently in older common, as are and inappropriate motor individuals with ID, may influence the assessment of behaviours (e.g. trying to leave home, or trailing of carers for orientation. 7,15,16 no apparent reason). can progress to Dementias that primarily affect the neo-cortex (e.g. overt hostility and aggression, often with unpredictable and Alzheimer’s disease, fronto-temporal dementia) tend to unprovoked explosions of primitive affect. Such behaviours affect language function. This may present as language use are a frequent cause of hospitalisation and that is uncharacteristically vague, stereotyped, clichéd, institutionalisation. 21 A decrease in motor or social repetitive, circumstantial, or impoverished. Word finding spontaneity is also common, and can occur at any stage of the difficulties are often early manifestations. There may be dementing process. Patients may display psychomotor increasing paraphrasic errors, a tendency to relate events in retardation or diminished spontaneous movement, remaining

African Journal of Psychiatry • July 2011 196 REVIEW Afr J Psychiatry 2011;14:194-199 sedentary for increasing periods of time. Social reciprocity cognitive decline. All types of previously learned skills of and volition may be affected, with reduced initiative or drive daily living may be affected. These include impairments in: for activities and interests, diminished interaction, and self-care, home-living, communication, functional academic emotional restriction. Distinct nocturnal worsening of skills, occupational performance, financial skills, social and behavioural presentation in the evenings (‘’) may leisure skills, capacity to use community resources, health and also be seen. The impact of such behavioural changes on all safety skills, and motor skills. aspects of home, social or occupational life should not be The assessment of adaptive behaviour and living skills is underestimated. It should also be remembered that often difficult. Although there are a number of instruments behavioural changes might be secondary to underlying, and available for this purpose 6,10,24 , most of these are informant- potentially reversible, medical conditions, environmental based reports, which are not always reliable, particularly in factors (e.g. changes in routine or living situation), institutional settings where staff may not be sufficiently psychosocial stressors (e.g. interpersonal conflict or familiar with the patient. Functional decline may impact bereavement) or co-morbid (e.g. significantly on the patient’s capacity to cope with basic or ). environmental, social or occupational demands. The decline Mood (especially depressive) and anxiety symptoms are usually starts with subtle and easily avoided skills (e.g. using commonly encountered in patients with ID and dementia. a telephone properly). Increasingly, the ability to function in Older adults with ID and dementia are known to be more ordinary life is lost, with decline in basic and essential skills, susceptible to depression (either as a first presentation or at such as those related to self-care, dressing, feeding and any stage in the course of dementia) than ageing individuals toileting. The degree and rapidity of decline depend on, in the general population. 13 Other mood-disordered states amongst other things, the individual’s level of pre-morbid (e.g. elation, hypomania, emotional disinhibition, irritability, intellect, the type and severity of the dementia, the presence mood lability, , adjustment reactions) do occur, but less of co-morbid illness, and the timing and efficacy of treatment. frequently than depression. 22 Associated disturbances of Individuals with ID, who may already be disadvantaged by neurovegetative features (e.g. , , significant pre-existing impairments in cognitive, reversed sleep-wake cycles), somatization (e.g. communicative and adaptive skills, are particularly vulnerable ), self-harming or suicidal ideation, or signs to profound decrements in their quality of life. Further of anxiety or distress may be present. Many restless, agitated, diminution of skills and abilities may also impact significantly or aggressive patients are, in fact, anxious or mood- on the resources of a care system that is often stretched to disordered. This is particularly important in those with more begin with. severe levels of ID, and those with poor verbal skills, who may not be capable of effectively communicating subjective states Examination of emotional distress. Management of the underlying Although the Mental State Examination (MSE) has some psychopathology should attenuate or resolve the behavioural limitations in the quantification of intellectual impairment, it difficulties. should provide, in conjunction with a detailed and focused Psychosis is an important component of the dementia history and physical examination, useful information for the syndrome in some patients, with approximately 28% of formulation of a sound initial clinical opinion. The specific intellectual disabled people with dementia experiencing at order and emphasis of the MSE may differ from patient to least one psychotic symptom at some stage. 4,23 are patient (or from interview to interview), and certain aspects most commonly of the persecutory type, and are usually may need modification, or may be inappropriate, for some simple, unsystematized and crude. are usually individuals with ID. Early identification and management of of the auditory or visual variety, the latter a frequent physical symptoms and signs is important in the ID occurrence in patients with Lewy body dementia. Other population, who are particularly prone to physical ill health perceptual disturbances that may occur include illusions and and complications, and generally more sensitive to adverse misidentification phenomena. effects of medication than others. Although physical, medical Changes in personality invariably occur with the and neurological complications tend to be late features in the development of dementia, especially in the types of dementia majority of patients, these may occur at any stage of the that have a predilection for the frontal and temporal lobes. illness. People with ID and dementia are susceptible to There may be an accentuation of pre-existing personality developing a number of medical problems 9,14,15,16,25,26,27 , traits. Patients may become more apathetic, passive, socially including: incontinence (urinary or faecal; usually nocturnal); withdrawn, disengaged, anxious, fearful, or unconcerned. gastrointestinal problems (e.g. chronic constipation; Similarly, interpersonal styles of interactions may change to diarrhoea); and dehydration; (e.g. being more disinhibited, egocentric, hostile, irritable, infections of the urinary or lower respiratory tract; bed sores); unpredictable, or aggressive. metabolic and endocrine disturbances (e.g. glucose or electrolyte imbalances); cardio-pulmonary complications Adaptive function (e.g. heart failure; atherosclerosis; hypertension; syncope; In addition to deficits in cognition and associated behavioural postural hypotension; chronic obstructive pulmonary and psychiatric features, dementia is always associated with a disease); neurological problems (e.g. seizures; sensory decline in adaptive functionality. The onset of dementia in impairments; dyskinesia's; paresis); musculoskeletal individuals with low pre-existing levels of intellectual and mobility difficulties (e.g. gait and balance disturbances; functioning is often reflected initially in changes adaptive falls); haematological problems (e.g. anaemia); inflammatory behaviour, rather than memory loss or other obvious conditions and neoplastic disease.

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Investigation age, though, there should be no significant disturbances of All patients suspected of developing dementia should be orientation, comprehension, language, general knowledge, investigated for disorders that could cause, exacerbate, or overall executive function, nor should there be any complicate or be confused with dementia. The choice of marked decline in levels of adaptive functioning. initial investigations is determined to a large extent by the Unsurprisingly, it is often very difficult to distinguish information already gathered on history and examination. between age-related cognitive decline and dementia, Whilst not always necessary, neuroimaging investigations particularly in people with ID, especially at lower levels of can be helpful, particularly in excluding some differential intellectual disability or in the presence of multiple sensory diagnostic options. CT scanning often reveals non-specific or physical impairments. 12 The literature on non- cortical atrophy and ventricular dilatation; MRI is useful pathological ageing in people with ID is scant. A significant where is suspected or for white matter difficulty relates to the fact that this is a highly pathology. Electro-encephalographic (EEG) findings of heterogeneous population, with individuals differing generalized slow wave activity are suggestive. markedly in terms of underlying aetiology, intellectual Interpretation of results in some people with ID may be profile, nature and extent of impairments, personalities and difficult: a relatively high proportion of abnormal social background. 20 A number of proposals have been put neuroimage or EEG findings may be related to the forward to help define and understand the ageing process underlying cause of ID, rather than the onset of dementia. It in ID 6,12,17,20,28 : is particularly helpful therefore to compare results with • General intellectual capacity in individuals with mild to previous investigations. Neuroimage and EEG investigation moderate levels of ID without seems to can be helpful in patients with more severe levels of ID, in remain intact until about 65 years of age (similar to the whom options for formal neuropsychological testing are general population). Early or marked cognitive decline often limited. When neuropsychological testing is possible, is usually related to specific medical, iatrogenic or valuable information on the pattern and extent of cognitive environmental factors. The degree of age-related impairment can be obtained, which will help clarify the cognitive decline in people with severe to profound ID diagnosis, guide management planning, monitor remains equivocal. progression and assist with prognostication. This • Deficits on IQ tests are often exacerbated by more notwithstanding, a significant obstacle is the fact that many pervasive problems in cognitive functioning (e.g. standard neuropsychological tests are not sensitive or difficulties with attention, arousal or motivation). specific enough to be used reliably to measure early or • Decline in cognitive skills, especially complex and subtle cognitive impairments in people with pre-existing abstract skills, may not directly parallel changes in intellectual impairments. adaptive functional skills. • People with initially lower cognitive and adaptive levels Differential diagnostic issues may appear to decline sooner with advancing age. It is essential to actively exclude as the cause of • Age-related changes in adaptive function are observed the presenting symptoms and signs. Distinguishing in ID populations (as in the general population), though between delirium and dementia may be difficult. The the issue is controversial. hallmark of delirium is disturbance of attention, usually of • Older adults living in institutional settings display more recent onset. There is alteration in the level of severe decline in adaptive skills than those living in consciousness or arousal, which is typically fluctuating in community settings. nature. There are often associated disturbances in other • Mobility and motor functioning appear to decline areas of cognitive function, perception, mood, and/or consistently with age in this group. behaviour. There may also be nocturnal exacerbation of symptoms, and sleep-wake cycle disturbances. To make Natural history and prognosis things more difficult, delirium-like presentations form part There is considerable individual variability in the evolution of some dementia syndromes (e.g. Lewy body dementia), of the dementia syndrome. The dementia may be and delirium may be co-morbid with dementia. Patients progressive, relapsing-remitting or relatively static. The with ID have higher rates of pre-existing medical and mode of onset and subsequent course are dependent on neurological abnormalities, and are known to be more the underlying aetiology, as well as the pre-existing and co- susceptible to the effects of systemic illness and to the morbid clinical profile of any given individual. This adverse effects of medication. This places such people at variability notwithstanding, the pattern of clinical evolution higher risk of developing delirium. 7,13 of dementia is commonly described using a three-stage Age-related cognitive decline may be associated with model, similar to that seen in the general population: (1) in mild memory decline, slightly shorter attention span, slower the early stages, cognitive, behavioural and psychiatric cognitive processing, and a slightly reduced capacity to symptoms are often subtle or episodic. Such changes may perform complex (especially novel) cognitive tasks. There be difficult to detect in people with ID. A decline of 8-10 IQ may also be subtle personality changes (e.g. reduced drive, points per year on test scores (e.g. the diminished interest in novelty, or conversely, heightened Wechsler Adult Intelligence Scale – WAIS) has been preference for routine and structure), mild sensory reported 9; (2) the middle stages present with progressively impairment (usually diminished sensory acuity), sleep- worsening cognitive impairment in a number of domains wake cycle disturbances (e.g. more nocturnal awakenings), (e.g. memory, language, praxis, complex cognition), and motor disturbances (e.g. postural changes). As people associated with significant and disabling decline in adaptive

African Journal of Psychiatry • July 2011 198 REVIEW Afr J Psychiatry 2011;14:194-199 functioning in important areas of daily living. Mood, Establishment of Criteria for the Diagnosis of Dementia in perceptual, behavioural and personality changes become Individuals with Intellectual Disability. J Intellectual Disability increasingly prominent, and there may be some neurological Research 2000; 44(2):175-80. fallout; and (3) the late stages, during which patients 11. Royal College of Psychiatrists. DC-LD: diagnostic criteria for eventually become significantly impaired in cognitive, psychiatric disorders for use with adults with intellectual psychiatric, physical and adaptive skill domains. Patients disabilities/mental retardation. London: Gaskell, 2001. become dependent on others to meet even the most basic of 12. Harper DC. A primer on dementia in persons with mental needs, and may become bed-bound. Physical and medical retardation: conclusions and current findings. In: Fletcher RJ and difficulties become more disabling and severe, with terminal Dosen A, eds, Mental health aspects of mental retardation: progress events usually related to cachexia, infections or in assessment and treatment. New York: Lexington, 1993: 169-98. cardiovascular aetiologies. 13. Evenhuis HM. The natural history of dementia in ageing people A number of prognostic factors can be identified among with intellectual disability. J Intellectual Disability Research people with ID who develop dementia. 9,12,13,17 These include a 1997; 41(1):92-6. family history of dementia; Down syndrome; early onset of 14. Evenhuis HM. Medical aspects of ageing in a population with symptoms, and late diagnosis or treatment; low pre-existing intellectual disability: mobility, internal conditions and cancer. J intellectual capacity or level of adaptive skills; severe Intellectual Disability Research 1997; 41(1):8-18. cognitive or behavioural symptoms and signs; co-morbid 15. Evenhuis HM. Medical aspects of ageing in a population with medical or neurological illness; iatrogenic factors (e.g. intellectual disability: I. . J Intellectual Disability chronic, multiple medication usage); and poor psychosocial Research 1995; 39(1):19-25. support systems (e.g. patients in institutional settings with no 16. Evenhuis HM. Medical aspects of ageing in a population with family contact). intellectual disability: II. Hearing impairment. J Intellectual Disability Research 1995; 39(1):27-33. Acknowledgements 17. Janicki MP and Jacobson J. Generational trends in sensory, physical, Acknowledgement is made to McKeith Press (London) for and behavioural abilities among older mentally retarded persons. copyright permission to use selected content from the American J Mental Deficiency 1986; 90(5):495-500. following book chapter: Nagdee M and O’Brien G. Dementia 18. Zigman W, Schupf N, Haveman M and Silverman W. The in . In: O’Brien G and Rosenbloom L, epidemiology of Alzheimer disease in intellectual disability: results eds, Developmental Disability and Ageing. London: MacKeith and recommendations from an international conference. J Press, 2009: 10-30. Intellectual Disability Research 1997; 41(1):76-80. 19. Zigman WB, Schupf N, Urv T, Zigman A and Silverman W. References Incidence and temporal patterns of change in 1. Janicki MP, Ackerman and Jacobson JW. State intellectual adults with mental retardation. American J Mental Retardation disabilities/aging plans and day-planning for an older intellectually 2002; 107(3):161-74. disabled population. Mental Retardation 1985; 23:297-301. 20. Holland AJ. Ageing and intellectual disability. British J of Psychiatry 2. Fisher K and Kettl P. Aging with mental retardation: increasing 2000; 176:26-31. population of older adults with MR require health interventions and 21. O’Brien G Seager M and Bell G. Re-admissions to intellectual prevention strategies. Geriatrics 2005; 60(4):26-9. disability hospitals: a study of failed discharge due to physical 3. American Psychiatric Association. Diagnostic and statistical manual health problems, relapsing mental illness and severe behavioural of mental disorders. 4th Edition (Text Revision). Washington DC: problems. Journal of Intellectual Disabilities 2000; 4: 321-332. American Psychiatric Association, 2000. 22. Burns A, Jacoby R and Levy R. Psychiatric phenomena in 4. Cooper SA. Psychiatric symptoms of dementia amongst elderly Alzheimer’s disease. III: Disorders of mood. British J of Psychiatry people with intellectual disabilities. International J Geriatric 1990; 157:81–6. Psychiatry 1997; 12: 662-6. 23. Burns A, Jacoby R and Levy R. Psychiatric phenomena in 5. Holland AJ, Hon J, Huppert FA, et al. Population-based study of the Alzheimer’s disease. I: Disorders of content. British J of prevalence and presentation of dementia in adults with Down’s Psychiatry 1990; 157:72–6. syndrome. British J of Psychiatry 1998; 172:493-8. 24. Deb S, Matthews T, Holt G, and Bouras N, eds, Practice guidelines 6. Nagdee M and O’Brien G. Dementia in developmental disability. In: for the assessment and diagnosis of mental health problems in O’Brien G and Rosenbloom L, eds, Developmental Disability and adults with intellectual disability. Brighton: Pavillion, 2001. Ageing. London: MacKeith Press, 2009: 10-30. 25. Moss S and Patel P. Dementia in older people with intellectual 7. Aylward EH, Burt DB, Thorpe LU, et al. Diagnosis of dementia in disability: symptoms of physical and mental illness, and levels individuals with intellectual disability. J Intellectual Disability of adaptive behaviour. J Intellectual Disability Research Research 1997; 41(2):152-64. 1997; 41(1):60-9. 8. Deb S and Janicki M. Conference report: international colloquium 26. van Schrojenstein Lantman-de Valk HM, van den Akker M, on mental retardation and Alzheimer’s disease. J Intellectual Maaskant MA, et al. Prevalence and incidence of health problems in Disability Research 1995; 39:149-50. people with intellectual disability. J Intellectual Disability Research 9. Janicki MP and Dalton AJ. Dementia in intellectual disabilities. In: 1997; 41(1):42-51. Bouras N, ed, Psychiatric and behavioural disorders in intellectual 27. Cooper SA. The relationship between psychiatric and physical disabilities and mental retardation. Cambridge: Cambridge health in elderly people with intellectual disability. J Intellectual University Press, 1999: 121-153. Disability Research 1999; 43(1):54-60. 10. Burt DB and Aylward EH. Test battery for the diagnosis of dementia 28. O’Brien G and Rosenbloom L, eds, Developmental Disability and in individuals with intellectual disability. Working Group for the Ageing. London: MacKeith Press, 2009.

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