Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, London
Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School and Camden and Islington Community Services NHS Trust, London
Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, London
Correspondence: Tim Stevens, Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, 2nd Floor, Wolfson Building, Riding House Street, London WIN 8AA, UK. Tel: 020 7288 5931; Fax: 020 7530 2304; e-mail: tim.stevens{at}ucl.ac.uk
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ABSTRACT |
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Aims To identify the distribution of dementia subtypes in a representative community population of older people.
Method People aged 65 years in randomised enumeration districts
in Islington, north London, were screened using a reliable and valid
questionnaire. People screened as having dementia were assessed in detail and
diagnoses were made according to standard diagnostic criteria.
Results Of 1085 people interviewed, 107 (9.86%) met screening criteria for dementia. Diagnoses were made for 72 people (67.3%). Distribution of subtypes varied according to the criteria used; the best-validated criteria yielding: Alzheimer's disease 31.3%; vascular dementia 21.9%; DLB 10.9%; and FLD 7.8%.
Conclusions Alzheimer's disease is confirmed as the most common cause of dementia in older people, followed by vascular dementia. However, DLB and FLD occur sufficiently often to be seen frequently in clinical practice and should be incorporated into future editions of standard diagnostic criteria.
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INTRODUCTION |
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METHOD |
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Sample selection
Stage 1
Participants were recruited from Islington, north London, which has a
Jarman under-privileged area score of 49, making it the sixth most deprived
area in England and Wales (Jarman,
1983). Enumeration districts (smallest unit of population into
which the UK is divided for the census) in Islington were selected randomly to
provide a sampling frame. Following an introductory letter, a researcher
visited each residence to ask whether a person aged 65 years or over was
present and available for an interview.
The shortened version of the Comprehensive Assessment and Referral Evaluation (Short-CARE; Gurland et al, 1984) was used to elicit psychiatric symptoms and diagnoses. This is a valid and reliable questionnaire with what are described as diagnostic scales for depression and dementia and a scale for activity limitation (designed to identify those who need help with day-today living). The scale for dementia has been validated against the outcome of worsening dementia or death.
Demographic data also were collected about each participant.
Stage 2
An experienced psychiatrist (T.S.) performed a follow-up assessment. Those
identified as screen-positive for dementia, defined as a score of 7 on the
dementia sub-scale of the Short-CARE, were asked to provide written consent to
undergo more detailed evaluation. If the participant was unable to provide
written consent, then the principal carer was asked to provide written assent
instead.
The evaluation consisted of:
Diagnostic criteria for classification of dementia
Two raters (G.L. and T.S.) jointly made diagnoses in accordance with
DSMIV (American Psychiatric
Association, 1994) and ICD10
(World Health Organization,
1992) criteria. Alzheimer-type dementia, vascular dementia,
dementia in Parkinson's disease and other/unspecified dementias were diagnosed
using these criteria.
In addition, diagnoses were made as follows:
The rater carrying out the clinical assessments (T.S.) made clinical diagnoses prior to the application of the above criteria. In particular, the diagnosis of DLB was made in the presence of progressive dementia with prominent well-formed visual hallucinations if one or both of the following features were present: spontaneous motor features of parkinsonism; pronounced fluctuation in cognitive performance. Evidence of cerebrovascular disease on history, physical examination or neuroimaging did not rule out the diagnosis unless there was a clear temporal relationship between a cerebrovascular accident and the onset of symptoms. Similarly, no restriction was imposed on the duration of Parkinsonian symptoms prior to the onset of dementia. These separate clinical diagnostic criteria were influenced by a post-mortem study by Hohl et al (2000), who reported a clinical diagnostic accuracy of 50% for DLB and found fewer hallucinations in the false-positive clinical cases, suggesting that hallucinations are an important diagnostic marker. This clinical approach to the diagnosis of DLB therefore differed from that taken by the consensus criteria in requiring the presence of visual hallucinations.
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RESULTS |
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Non-participants
Of the 197 people not interviewed, 64.3% were female. The reasons for
non-participation were: 153 (77.7%) refused an interview, 16 (8.1%) could not
be contacted, 15 (7.6%) did not speak English, 2 (1.0%) had other
communication problems and for 11 (5.6%) a relative refused on their
behalf.
Participants
The rest of the paper refers to those who participated. Ages ranged from 65
to 102 years, with a mean of 75 years, and 644 participants (59.4%) were
female. A total of 1031 (95%) lived at home in privately owned, rented or
sheltered accommodation, with the remaining 54 (5%) occupying residential or
nursing care facilities; 507 participants (46.7%) lived alone.
Of the 1085 people screened, 107 (9.86%) scored as screen positive on the dementia scale of the Short-CARE and 71 (66.4%) of these were female. The age range was 65-102 years (median 74 years).
Sixty-nine people (64.5%; 95% CI 56-73%) lived in rented, sheltered or owner-occupied accommodation. Thus, the screened prevalence rate of dementia for those who lived in the community without 24-hour care was 6.7% (95% CI 6-9%). Thirty-eight people (35.5%; 95% CI 28-45%) lived in residential or nursing care. The screened prevalence rate for dementia in those with 24-hour care was therefore 70.4% (95% CI 57-81%). Sixty-seven people screened as having dementia (62.6%) were born in the UK, 17 (15.9%) in Africa or the Caribbean, 8 (7.5%) in Cyprus, Greece or Turkey, 5 (4.7%) in Ireland, 5 (4.7%) in other European countries and 5 (4.7%) in other countries outside Europe.
Stage 2
Hospital notes were obtained for 84 (78.5%) of the 107 people screened in
stage 1 as having dementia and 64 (59.8%) subsequently were assessed in
person; 10 people (9.3%) refused further evaluation, 16 (15%) had died and 17
(15.9%) were not traceable. Eight (80%) of the people who refused further
evaluation were female. In three cases the people themselves refused, saying
they did not want to answer any more questions. In all other cases a family
member refused to allow their relative to be interviewed, the most common
reason given being that the relative was unlikely to benefit from further
assessment. The mean age was 82.3 years for people who had died, 81.6 years
for those who were not contactable and 78.9 years for those who refused.
Fourteen (87.5%) of the people who were dead at the time of attempted
follow-up had lived at home when first seen, compared with two (12.5%) in
residential care. Of those who refused, eight (80%) lived in rented or their
own accommodation and one each in nursing and residential care.
Demography
The mean age of the 64 people evaluated further was 80.0 years and 40
(62.5%) of these were female: 39 (60.9%) lived in rented or owner-occupied
accommodation, 2 (3.2%) in a nursing home and 23 (35.9%) in residential care.
The mean time between interviews for stage 1 and stage 2 was 8.8 months.
Diagnoses
Sufficient information for clinical diagnoses to be made was obtained from
the medical case notes, social services' reports, general practitioners and
relatives of eight of the people who were not interviewed after the initial
screening. Diagnoses thus were made for a total of 72 people (67.3% of the
original 107 who scored above the screening cut-off for dementia).
Table 1 indicates the numbers and proportions of people fulfilling the different diagnostic criteria. Not applicable is used where a diagnostic category is not included in a particular classification system. Alzheimer's disease includes all formulations for dementia of the Alzheimer's type in DSMIV and dementia in Alzheimer's disease in ICD10. Similarly, vascular dementia includes all sub-categories under this heading in DSM and ICD. Mixed dementia includes cases fulfilling DSMIV criteria for dementia due to multiple aetiologies and other/unspecified dementia, cases of dementia in other medical conditions specified elsewhere and dementia not otherwise specified in DSMIV.
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The results reveal Alzheimer's disease to be the most common cause of dementia by both DSMIV and ICD10 criteria. In addition, the majority of the sample fulfilled NINCDSADRDA criteria for either possible or probable Alzheimer's disease. The second most common diagnosis, again by both DSM and ICD criteria, was vascular dementia, with one-third meeting the NINDSAIREN criteria for possible or probable vascular dementia. The majority of people diagnosed with unspecified dementia were those with severe dementia on whom insufficient collateral information was available with regard to onset and course of the illness for a probable aetiology to be identified.
Almost 10% of the sample fulfilled the consensus criteria for probable DLB, 30.5% fulfilling criteria for either probable or possible DLB. Of the cases of probable DLB, four (57.1%) met the DSMIV criteria for Alzheimer's disease and one (14.3%) each met the DSM criteria for vascular dementia, dementia due to Parkinson's disease and unspecified dementia. Identical results were seen when probable DLB cases were compared with their ICD10 diagnoses. In contrast, a clinical diagnosis of DLB based on the criteria described above, namely with emphasis on visual hallucinations and more flexible assessment of the time of onset of symptoms and contribution of vascular factors, was made in five cases (6.9%). All five cases fulfilled the consensus criteria for probable DLB.
Four people (5.6%) met the Gregory and Hodges criteria for FLD, compared with six (8.3%) who fulfilled the consensus criteria for frontotemporal dementia. All four Gregory and Hodges cases also met the consensus criteria. A comparison of diagnoses made using these two sets of criteria with the DSMIV diagnoses is shown in Table 2.
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Eight people (11.1%) did not meet the DSMIV criteria for dementia. Two did not have memory impairment, one of whom had an FLD and one of whom had English as her second language. Three were depressed and three had cognitive dysfunction but no significant impairment in social or occupational function due to cognitive deficit. Table 3 shows the numbers and proportions of people fulfilling the different diagnostic criteria once those not meeting DSM dementia criteria have been excluded. No DLB consensus cases of probable or possible DLB have been excluded (i.e. all of these cases met the DSM criteria for dementia). The proportions of people with probable DLB and probable plus possible DLB are thus higher, namely 10.9% and 34.4%, respectively. As noted above, one person fulfilling both sets of criteria for FLD was excluded. Table 4 indicates the DSM diagnoses of the remaining Gregory and Hodges and FTD consensus criteria cases of DFT/FTD.
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Three people (4.7%) who met the DSM criteria for dementia did not fulfil the ICD10 criteria because they had not been suffering clearly from the disorder for 6 months or more.
Figure 1 indicates the degree of diagnostic overlap for cases meeting the DSM criteria for dementia. For example, a person fulfilling the consensus criteria for probable DLB but also the NINCDSADRDA, DSM and/or ICD criteria for Alzheimer's disease would fall in the area of overlap between DLB and Alzheimer's disease. The category unspecified dementia has been excluded because this does not represent a diagnostic entity. The single cases of pure DLB and FLD (i.e. those not lying in an area of overlap) had been diagnosed as unspecified dementia by DSM and/or ICD. Cases of mixed dementia have been included in the area of overlap between Alzheimer's disease and vascular dementia, because these were judged to be the combined aetiologies in each instance.
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DISCUSSION |
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Limitations
These figures are not immutable because the distribution of the different
subtypes differs considerably, depending on the criteria used. Our results are
restricted by the numbers of people identified at screening as having dementia
on whom we could not make a diagnosis. The Short-CARE has not been validated
as an instrument on people who have dementia without significant memory
impairment and we do not know to what extent this may have influenced our
findings, although we did detect some people with this syndrome. In addition,
it is a limitation of the study that post-mortem diagnoses were not
available.
A relatively high proportion (11.1%) of people identified by initial Short-CARE screening did not have dementia according to DSMIV. For three of these eight people there was insufficient evidence of impairment in social or occupational functioning for dementia to be diagnosed, despite clear evidence of cognitive impairment in multiple domains. Because this was an epidemiological study, we employed a screening instrument and, subsequently, diagnostic criteria that produced categorical outcomes. Caution, however, clearly needs to be exercised in the use of these criteria in clinical practice in order to avoid excessively strict adherence to the inclusion and exclusion requirements at the expense of common sense.
Clinical implications
Previous studies of the frequency of DLB have concentrated on hospital
in-patient or out-patient populations and, in particular, on the
epidemiologically unrepresentative cohorts that come to post-mortem. It is
highly likely that many of the figures from published studies on the
distribution of other dementia subtypes are contaminated by DLB cases,
particularly as neither of the two major classification systems currently in
use, DSMIV and ICD10, include the diagnosis of DLB. Most cases
of probable DLB in this study were diagnosed as having
Alzheimer's disease using DSMIV and ICD10. Almost one-third of
the sample fulfilled DLB consensus criteria for either probable
or possible DLB. This suggests that the consensus criteria are
broad, at least with regard to the diagnosis of possible DLB.
The clinical criteria used to diagnose DLB, which simultaneously
were more restrictive in requiring the presence of visual hallucinations and
more flexible in leaving unspecified the time relationship between the onset
of parkinsonism and that of dementia, yielded a lower rate for this
disorder.
As with DLB, neither DSMIV nor ICD10 permits the diagnosis of FLD, although both include Pick's disease as a possible aetiology. Because other aspects of cognition and activities of daily living are relatively preserved in early FLD, our rates may be conservative in that some cases may have been missed using a screening test that relies on orientation, memory and independence in activities of daily living (Gregory & Hodges, 1996). There are suggested ways of overcoming this problem using additional bedside tests (Gregory et al, 1997). In our study, FLD was diagnosed more often using consensus criteria than the Gregory and Hodges criteria. This may be due to disagreement about the terminology used to describe these dementias: some groups prefer frontotemporal dementia (Brun et al, 1994) whereas others regard this term as including disparate conditions and so prefer dementia of frontal type (Gregory et al, 1998). Both sets of criteria used in our study are weighted towards a purely degenerative aetiology of FLD and exclude the possibility of a vascular contribution to symptoms.
Our results indicate that it is possible to determine a probable aetiology in most cases of dementia. The relatively small degree of overlap of the Alzheimer's disease and vascular dementia categories, as shown in Fig. 1, indicates that the diagnostic systems in current use lead to the same diagnostic conclusions for most individuals. This, however, is only true for Alzheimer's disease and vascular dementia.
The ability to distinguish particular subtypes of dementia is important for several reasons. It enables clinicians to identify associated risk factors, to implement specific treatment strategies, to inform patients and relatives more accurately of the prognosis of each one and to provide relevant services. This is particularly pertinent in the light of the development of treatments such as the cholinesterase-inhibiting drugs for Alzheimer's disease. The demand for these drugs, together with their high cost, requires accuracy of diagnosis and standardisation of diagnostic criteria. The inability of DSM and ICD to identify DLB and FLD, which are relatively common forms of dementia, means that they do not suffice to categorise these conditions. Both DLB and FLD should be incorporated in future editions of standard diagnostic criteria.
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Clinical Implications and Limitations |
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LIMITATIONS
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REFERENCES |
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Borkowski, J. G., Benton, A. L. & Spreen, O. (1967) Word fluency and brain damage. Neuropsychologica, 5, 135-140.[CrossRef]
Brun, A. (1987) Frontal lobe degeneration of non-Alzheimer's type 1. Neuropathology. Archives of Gerontology and Geriatrics, 6, 209-233.[Medline]
Brun, A., England, B., Gustafson, L., et al (1994) Consensus statement. Clinical and neuropathological criteria for frontotemporal dementia. Lund and Manchester groups. Journal of Neurology, Neurosurgery and Psychiatry, 57, 416-418.[Medline]
Copeland, J. R. M., Kelleher, M. J., Kellet, J. M., et al (1976) A semi-structured clinical interview for the assessment and diagnosis of mental state in the elderly: the Geriatric Mental State Schedule 1. Psychological Medicine, 16, 89-99.
Erkinjuntti, T., Ostbye, T., Steenhuis, R., et al
(1997) The effect of different diagnostic criteria on the
prevalence of dementia. New England Journal of
Medicine, 337,
1667-1774.
Folstein, M. F., Folstein, S. E. & McHugh, P. R. (1975) Mini-Mental State: a practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12, 189-198.[CrossRef][Medline]
Forno, L. S. & Langston, J. W. (1988) The amygdalaparahippocampal region: a predilection site for Lewy bodies. Journal of Neuropathology and Experimental Neurology, 47, 354.
Galasko, D., Hansen, L. A., Katzman, R., et al (1994) Clinicalneuropathological correlations in Alzheimer's disease and related dementias. Archives of Neurology, 51, 888-895.[Abstract]
Gold, G., Giannakopoulos, P., Montes-Paixo-Junior, C., et al (1997) Sensitivity and specificity of newly proposed clinical criteria for possible vascular dementia. Neurology, 49, 690-694.[Abstract]
Gregory, C. A. & Hodges, J. R. (1993) Dementia of frontal type and the focal lobar atrophies. International Review of Psychiatry, 5, 397-406.
Gregory, C. A. & Hodges, J. R. (1996) Dementia of frontal type: use of consensus criteria and prevalence of psychiatric features. Neuropsychiatry, Neuropsychology and Behavioural Neurology, 9, 145-153.
Gregory, C. A., Orrell, M., Sahakian, B., et al (1997) Can frontotemporal dementia and Alzheimer's disease be differentiated using a brief battery of tests? International Journal of Geriatric Psychiatry, 12, 375-383.[CrossRef][Medline]
Gregory, C. A., McKenna, P. J. & Hodges, J. R. (1998) Dementia of frontal type and simple schizophrenia: two sides of the same coin? Neurocase, 4, 1-6.[CrossRef]
Gurland, B., Golden, R. R., Teresi, J. A., et al (1984) The Short-CARE: an efficient instrument for the assessment of depression, dementia and disability. Journal of Gerontology, 39, 166-169.[Medline]
Hachinski, V. C., Ilif, L. D., Zilcha, I. E., et al (1975) Cerebral blood flow in dementia. Archives of Neurology, 32, 632-637.[Abstract]
Hohl, U., Tiraboschi, P., Hansen, L. A., et al
(2000) Diagnostic accuracy of dementia with Lewy bodies.
Archives of Neurology,
57,
347-351.
Jarman, B. (1983) Identification of underprivileged areas. BMJ, 286, 1705-1709.[Medline]
Jorm, A. F., Korten, A. E. & Henderson, A. S. (1987) The prevalence of dementia: a quantitative integration of the literature. Acta Psychiatrica Scandinavica, 76, 465-479.[Medline]
Lim, A., Tsuang, D., Kukull, W., et al (1999) Clinico-neuropathological correlation of Alzheimer's disease in a community-based case series. Journal of the American Geriatric Society, 47, 564-569.
Lobo, A., Launer, L. J., Fratiglioni, L., et al (2000) Prevalence of dementia and major subtypes in Europe: a collaborative study of population-based cohorts. Neurologic Diseases in the Elderly Research Group. Neurology, 54 (suppl. 5), s4-s9.[Medline]
McKeith, I. G., Galaski, D., Wilcock, G. K., et al (1995) Lewy body dementia diagnosis and treatment. British Journal of Psychiatry, 167, 709-717.[Medline]
McKeith, I. G., Ballard, C. G., Perry, R. H., et al
(2000) Prospective validation of consensus criteria for the
diagnosis of dementia with Lewy bodies. Neurology,
54,
1050-1058.
McKhann, G., Drachman, D., Folstein, M., et al (1984) Clinical diagnosis of Alzheimer's disease: report of the NINCDSADRDA Work Group under the auspices of the Department of Health and Human Services Task Force on Alzheimer's disease. Neurology, 34, 939-944.[Abstract]
Neary, D., Snowden, J. S., Gustafson, L., et al (1998) Frontotemporal lobar degeneration. A consensus on clinical diagnostic criteria. Neurology, 51, 1546-1554.[Abstract]
Oliva, R. (2000) Genetica de la demencia frontotemporal y alteraciones del gen tau. Neurologia, 15 (suppl. 1), 33-37.[Medline]
Reitan, R. M. (1958) Validity of the trail making test as an indicator of organic brain damage. Perceptual and Motor Skills, 8, 271-276.
Roman, G. C., Tabemichi, T. K., Erkinjuntii, T., et al (1993) Vascular dementia: diagnostic criteria for research studies. Report of the NINDSAIREN international workshop. Neurology, 43, 250-260.[Abstract]
Shallice, T. & Evans, M. E. (1978) The involvement of the frontal lobes in cognitive estimation. Cortex, 14, 294-303.[Medline]
Stern, M. B. (1988) The clinical characteristics of Parkinson's disease and parkinsonian syndromes: diagnosis and assessment. In The Comprehensive Management of Parkinson's Disease (eds M. B. Stern & H. I. Hurtig), pp. 3-50. New York: PMA Publishing Corporation.
World Health Organization (1992) Tenth Revision of the International Classification of Diseases and Related Health Problems (ICD10). Geneva: WHO.
Yamada, T., Hattori, H., Miura, A., et al (2001) Prevalence of Alzheimer's disease, vascular dementia and dementia with Lewy bodies in a Japanese population. Psychiatry and Clinical Neurosciences, 55, 21-25.[CrossRef][Medline]
Received for publication March 15, 2001. Revision received August 29, 2001. Accepted for publication October 1, 2001.
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