Published for the British Institute of Learning Disabilities
Journal of Applied Research in Intellectual Disabilities 2014, 27, 555–563
Ageing and Dementia in a Longitudinal Study of a Cohort with Down Syndrome Janet Carr* and Suzanne Collins† *Gaston Cottages formerly at St George’s Hospital, Cranmer Terrace, London SW170RE, UK; †Honorary Senior Lecturer, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
Accepted for publication 1 January 2014
Background A population sample of people with Down syndrome has been studied from infancy and has now been followed up again at age 47 years. Methods Intelligence and language skills were tested and daily living skills assessed. Memory/cognitive deterioration was examined using two test instruments. Results Scores on verbal tests of intelligence changed little. Those on a non-verbal test, on self-help skills and on both memory tests showed some decline, even when the scores of those already suffering from dementia were discounted.
Introduction That older people with Down syndrome are more vulnerable to cognitive deterioration than are either those in the general population or those whose intellectual disabilities are ascribed to other causes is now well accepted (Dalton & Crapper 1977; Burt et al. 1995). Nevertheless, it is also well established that only a proportion of people with Down syndrome, however long-lived, will suffer from the condition (Oliver et al. 1998; Silverman et al. 1998; Janicki & Dalton 2000). It becomes pertinent then to try to identify, first, the trajectory of any cognitive decline in people with Down syndrome who do not progress to dementia; and second, the factors that may distinguish those showing only the effects of normal ageing from those in the early stages of dementia. Burt et al. (1995) studied two groups of people with intellectual disabilities, one group with and another without Down syndrome, over 3–5 years. Aiming at ‘a study of typical ageing’, they excluded any who showed three or more signs of dementia, excluding almost three times as many people with Down syndrome as of those in the comparison group. Only one factor, verbal fluency, demonstrated decline unique to those with Down © 2014 John Wiley & Sons Ltd
Conclusions At age 47, scores on most tests of even the majority of the cohort (i.e. those not definitely diagnosed with dementia) showed some decline. While this includes the scores of people who may subsequently develop dementia, it may also reflect the normal ageing process in this population. Keywords: dementia, Down syndrome, longitudinal
syndrome. Older people in both groups showed declines in community living and on delayed memory. The authors comment that, while consistent with those of other research, in that difference is more likely to be found on more complex tasks, these findings should be interpreted cautiously because of the confounding of age and cohort in crosssectionalcomparisons. Devenny et al. (2000) carried out a prospective study of 44 adults with Down syndrome, using the WISC-R, which was given twice over at least 4 years, omitting the picture arrangement and similarities subtests because of baseline floor effects. Participants divided into four groups, one that remained healthy (and was on average at least 6 years younger than the other three) and three with differing degrees of dementia, characterized as ‘questionable’, ‘early’ stage and lastly ‘middle’ stage. Scores of participants in the ‘healthy’ group were distinguished from those in each stage of dementia on block design and coding; from the combined dementia groups on object assembly, picture comparison, arithmetic and comprehension; and from those in the middle stage of dementia on vocabulary and digit span. Thus, in this study, two WISC subtests, block design and coding, were the most sensitive to cognitive decline [block design having been similarly implicated by Gibson et al. (1988)]. Devenny 10.1111/jar.12093
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et al. (2000) characterize these two tests as requiring ‘perception of visual stimuli, visual organization and visuomotor coordination’ which appear to be ‘more vulnerable to decline related to dementia’. By contrast, information and vocabulary, relying on ‘semantic memory’, and digit span, relying on short-term memory, were relatively well preserved. Behavioural changes, as indications of dementia, have been identified in several studies. Holland et al. (2000) found the emergence of behavioural and personality problems preceded the findings of neurological signs, and Ball et al. (2008) found that in a pre-clinical group changes in personality or behaviour were more common than memory changes. Oliver et al. (2011), stressing that changes in behaviour are as important as are neurological signs, showed both behavioural excesses (crying, restlessness, aggression) and deficits (inactivity, disorientation, becoming lost) to occur more often in people with Down syndrome with dementia than in either an older, non-demented group or in a younger group of people with Down syndrome. Urv et al. (2008) also found an excess of maladaptive behaviours (aggression, fearfulness, sleep problems) in people with Down syndrome in the early stages of dementia while in Prasher and Filer’s (1995) study problem behaviours (not including aggression) occurred significantly more often in the demented people. A group of 30 people with Down syndrome studied by Adams and Oliver (2010) showed an increase in behavioural excesses and poorer executive function, but no significant change in adaptive skills, in those developing cognitive deterioration. Prasher and Filer, however, found a demented group to be significantly poorer in feeding and washing skills and in the occurrence of urinary incontinence than was the case with the non-demented group. In a study focussing not on the approach of dementia but on differences in the ageing process between those with and without Down syndrome, Esbenson et al. (2008) report on a longitudinal project carried on over 9 years. There were 150 people with Down syndrome and another group with intellectual disabilities due to other causes whose ages went from 19 to 68 years (mean age 36 years). Changes in health, functional abilities and behaviour problems were assessed but not cognitive ability. There was a (non-significant) ‘trend’ for the health of the Down syndrome group to decline with age, although four out of five remained in ‘excellent health’ by the end of the study, when mean age was 44 years. Bertoli et al. (2011), also not concerned with dementia, studied a large group, 518, of people with Down syndrome, ages ranging from 0 to 63 years (mean age,
calculated from data provided, 24 years) and found that while the children enjoyed a wide range of social experiences, for adults these became markedly more limited, leading to an emphasis on a routine of homebased activities. The present study was intended to provide further information on the ageing and/or dementing processes in a population of people with Down syndrome for whom longitudinal data are available.
Method A population sample of babies with Down syndrome born in 1 year (December 1963–November 1964) in one geographical area has been seen and tested by the first author at age 6 weeks and at intervals to 21 and 30 years, and then at 5 year intervals to 45 years (Carr 1975, 1995, 2000, 2003, 2012). At the most recent time, two people were confirmed, by the medical personnel involved with them, as having dementia, and six others were thought, by their carers and on the grounds of the tests used on successive occasions, to be possibly showing the early signs of the disease. All at that time were women. Following consultation with Prof. Tony Holland, it was decided to carry out the next follow-up after two rather than 5 years. Accordingly all those still available were seen at age 47. Table 1 shows the losses to the study over 47 years (from the original total of 54). Of the 30 people seen at age 45, the father of one man said he and his son no longer wished to be involved, leaving 29 participants at age 47. 21 people were seen by the first author and eight by Dr Suzanne Collins. They were given most of the same tests as had been used from age 30 years to 45 years – the Leiter International Performance Scale (LIPS), the British Picture Vocabulary Scale (BPVS), the vocabulary scale from the Wechsler Pre-School and Primary Scale of Intelligence (WPPSI); and two tests of memory/dementia, the Neurological Assessment of Dementia in Individuals with Intellectual Disability (NAID, Adams & Oliver 2010) formerly known as the Oliver & Crayton Dementia Battery and the Rivermead Behavioural Memory Test for Children (RBMT-C, Wilson & Ivani-Chalian 1995). Daily living Table 1 Number, cause and timing of losses to the study from birth to 47 years Age, before (years) Deaths Withdrew Moved, address withheld
4 8 1
21 3 1
30 2
40 4
47 4 1
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skills were assessed using the handicaps, behaviour and skills schedule (HBS, Wing 1980), scores in this case being the sums of the raw scores as set out by Wing. Tests of reading, writing and arithmetic, which had been used from age 21 to age 45, were omitted. The tests used were chosen to examine as wide a range of abilities as possible and to be accessible to as many as possible of the participants. In the case of the vocabulary test, the WISC (for older children) was attempted at age 21 but was too difficult for all but a tiny minority (five of the high achieving women) to make a score on it. It seemed out of the question to attempt the related adult Wechsler scale. The NAID and RBMT-C have been described in detail elsewhere (Carr 2003). Briefly, the NAID consists of seven subtests; three of memory – of pictures, objects and sentences of increasing length; picture identification and naming; carrying out simple requests (‘clap your hands’) and of orientation. The RBMT-C consists of eleven tests of memory – of the first and second names of a person shown in a photograph; of an object which is shown and then hidden at the start of the test, and an instruction to request another appointment, both to be recalled at the end of the test; of pictures of objects and faces; a short story and route, this including a message to be picked up and replaced, all to be recalled both immediately and after a delay; and a test of orientation for time and place. Over a third of the people still lived at home, most with a surviving parent but two each with either a brother or a sister, the remaining 64% being in charity, health or social services facilities. Over half attended a Social Education Centre; two people also attended further education courses part-time. None now was in work.
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same 29 people, from age 21 to age 47, are shown in Figure 1A, for the whole group, and for men women. Figure 1A shows that, in the whole group, mean IQs declined by nearly nine points over the 26 year period; that for the men by 3.5 points; and that for the women by over 11 points. This figures include those for the two women who at 45 were seriously affected by dementia. If these two are excluded the figures are as follows (scores for the men are unaffected) (Figure 1B). Even for those without confirmed dementia, the loss for the women from age 21 was 6.7 IQ points, (z = 2.40, P = 0.016) and for the whole group 5.1 points. This compares with a loss, at 45 years, for the whole group of 1.4 points and no loss at that time by the men (Carr 2012).
(A)
(B)
Results Except where otherwise stated, all results are given only for those people who featured at every stage of the study (i.e. those who were still in the study at age 47). Where statistical significance is indicated, all tests are two-tailed. Apart from IQs and MAs, other scores, on the NAID and RBMT-C, as well as on the self-help scale, are raw scores.
Intellectual and self-help abilities On this occasion, 2 years after the last report, changes in average scores on non-verbal ability were more apparent than they had previously been. Average IQs on the Leiter International Performance Scale, on the © 2014 John Wiley & Sons Ltd, 27, 555–563
Figure 1 (A) Leiter IQs for all, and for men and women. (B) Leiter IQs for those not diagnosed with dementia, all and women.
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In contrast to the results on non-verbal ability, for those able to score on the tests, no decline in verbal ability scores was seen. Figure 2 shows the results from the BPVS test. Following a small rise from age 21 to 30 years, scores fluctuated by 3–4 months, in both the men and the women and in the two groups combined.
Figure 3 shows scores on the WPPSI vocabulary test (expressive language). Scores for the whole group peaked at age 30 and then fluctuated, while those for the men declined somewhat, being 8.5 months below the 30-year level at both ages 40 and 47. Total scores on the self-help skills scale, from age 11 to age 47, are shown in Figure 4A. The figure shows that, from a peak at age 30, by age 47 the whole group lost 4.4 points, the men 1.6 and the
(A)
Figure 2 BPVS age (months MA) for all, and for men and women. Note: those with confirmed dementia are not included as they did not make a score at age 47.
(B)
Figure 3 WPPSI vocabulary ages (months MA) for all, and for men and women. Note: those with confirmed dementia are not included as they did not make a score at age 47.
Figure 4 (A) Total self-help skills, for all, and for men and women (maximum score = 58). (B) Total self-help skills for those not diagnosed with dementia, for all and for women (maximum score = 58). © 2014 John Wiley & Sons Ltd, 27, 555–563
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women 6.9 points. These include the figures for the two women who at 45 had been diagnosed with dementia. If these are excluded the figures are shown in Figure 4B (scores for the men are unaffected). Setting aside the scores of the two women with dementia, the loss for the whole group from age 30 was 2.3 points and that for the women 2.5 points. Results from the tests of memory/dementia, for those able to make a score on the tests, are shown in Figures 5 and 6.
Figure 5 Mean scores on the NAID, for all and for men and women.
Figures 5 and 6, which do not include scores of those confirmed with dementia, show that, from the peak figures attained at ages 35–40, the loss on the NAID, for the whole group, was 9.9 points (of the order of 14%); for the men, 8.3 points (13%); and for the women, 12.5 points (16%). For the RBMT-C, from a peak at age 40, the equivalent losses were, for the whole group, 13.1 points (30%); for the men, 7.2 points (20%); and for the women from a peak at ages 35 and 40, 19 points (38%). Thus, even for those not currently with confirmed dementia, these tests show some falling off in performance, this being shown rather more clearly by the RBMT-C than in the NAID and being more pronounced in the women; the loss for the men just fails to reach significance (z = 1.87, P = 0.060), but that for the women is significant (z = 2.44, P = 0.016). Looking at score changes for individuals: of the six women identified at age 45 as possibly showing the early signs of dementia, at 47, this was not confirmed for two; each had slightly increased scores on both tests of dementia, one also on both verbal and non-verbal intelligence, while for the other, these scores had declined somewhat. The remaining four showed marked declines on both dementia tests, of between eight and 39 points on the NAID and of between 21 and 40 points on the RBMT-C. Three also showed declines on the nonverbal test (the mother of one woman had consulted her GP about her concern regarding her daughter’s shortterm memory, but had had her worries played down by the GP who attributed these difficulties to the menopause). With one exception,1 no other member of the cohort had declines of these magnitudes on both tests. These four then are regarded as being probably in the early stages of dementia. On this most recent occasion, the scores of one man also gave rise to concern. Since age 35 (i.e. at ages 40, 45 and 47), he had been increasingly unco-operative in the test situation. His scores on the NAID were 53 and 43 at ages 40 and 45, while at age 47 it was not possible to get a response from him on the test. This has also been the case with him at all three ages on the RBMT-C. On the non-verbal IQ test, his scores declined from 53 at age 40 to 36 at age 45 and approximately 22 at age 47. In addition, his movements have become notably
1
Figure 6 Mean scores on the RBMT-C, for all, and for men and women. © 2014 John Wiley & Sons Ltd, 27, 555–563
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This is a man who, 15 months earlier, had been found to have an advanced cancer, had had extensive treatment and was given not more than 5 years to live. Although currently stable, he is ‘so tired all the time’ and all his activities are greatly restricted and reduced.
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awkward and slow. He too should now be regarded as being probably affected by dementia. With the two already diagnosed with dementia, there are now seven people in the affected, ‘dementing,’ group, to be distinguished from the remaining 22 ‘healthy’ people. The scores of these two groups, on the two tests of dementia, are shown in Figure 7. In each group, the scores are of those able to participate in the tests. Scores at age 30 on both tests were nearly 20 points higher for the ‘dementing’ group; at age 47, on the NAID, those for the ‘dementing’ group were identical to those of the ‘healthy’ group, while on the RMBT-C they were 20 points lower, although the difference is not significant. A number of other factors, implicated in other research or thought to be with the potential to be affected by the ageing process, were examined. Aggression, noted as increasing with the onset of dementia (Oliver et al. 1998; Urv et al. 2008), showed no increase in the present study population, nor in the seven with suspected/confirmed dementia. Health of the group declined slightly but not significantly, as has been shown in other studies (Esbenson et al. 2008). Vision deteriorated, 82% of the 47-year-olds compared with 50% of the 30-year-olds being said to have poor or very poor vision, but the difference is not significant. Hearing also declined, 55% being said to have normal hearing at age 47 compared with 79% at age 35, and this difference is significant (z = 2.54, P = 0.02).
Figure 7 Mean scores on the NAID and RBMT-C for ‘healthy’ and ‘dementing’ groups. For the ‘healthy’ group n = 18 throughout. For the ‘dementing’, NAID, ages 30–40, n = 7, age 45, n = 5, age 47, n = 4. RBMT-C, age 30–35, n = 7, age 40, n = 6, ages 45–47, n = 4.
Four carer-assessed variables, thought to have the possibility of distinguishing between the ‘healthy’ and the ‘dementing’ group, were examined: total self-help, domestic skills, independence – how far the person could go from the house alone - and health, at ages 30–47 years, for each of these two groups (see Figure 8). At age 30, one of the differences, that for independence, was significant, the advantage being to the ‘dementing’ group, the remainder being non-significant. At age 47, all were significant at P = 0.01–0.04, the advantage being to the ‘healthy’ group in all cases. Considering the individual items that make up the selfhelp scale (feeding, washing, dressing, toiletting), mean scores for the ‘healthy’ group declined by one point or less from age 30 to 47 while those for the ‘dementing’ group declined quite regularly over the 17 year period and were below the means for the ‘healthy’ group from age 40 onwards, but the differences do not reach significance.
Discussion The current phase of the study was carried out 2 years after the preceding one, instead of the 5 year gap that had been the case over the previous decades, due to concerns over the declining abilities of some members of the cohort. For two of these, continuing decline was not found, but was for the other six, while the scores of another at 47 led to his being included in the seven now with confirmed or suspected cognitive deterioration. This group now constitutes almost a quarter of the surviving study population. In the remaining 22, there were now some small score declines. On the non-verbal test, the loss from age 21 to age 47 was, for the ‘healthy’ group, just over five IQ points; for the men, 3.5 points; and for the women, nearly seven points, this last being statistically significant. Nevertheless, the loss remains only about a third to half of that expected of the nondisabled population over a similar period, in whom a loss of five IQ points per decade is found (Carr 2005). On verbal tests, and in contrast with the finding that, in the general population, crystallized intelligence ‘tends to maintain or improve slightly through the late 60s and, occasionally, the early 70s’ (Kaufman 1990, p;.195), in other studies of people with Down syndrome verbal ability has been seen to decline with age. These studies were carried out over varying periods, from 3 to 4 years (Burt et al. 1995) to 22 years (Haxby 1989). All showed declines, and three, covering about 7 years each, showed percentage declines of 17% (Kittler et al. 2004), 21% (Devenny et al. 2000) and 36% (Fenner et al. 1987). © 2014 John Wiley & Sons Ltd, 27, 555–563
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Figure 8 Mean scores from age 30 to age 47 on carer-assessed factors for ‘healthy’ and ‘dementing’ groups.
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Compared with these, the picture offered by the present study is different, over a similar period to that covered by the three mentioned above (age 40–47) and using the same test instrument (BPVS) mean score rose by 1%. The reason for this difference, of the present study from the three others, is not clear. Two possible reasons were considered: where the study populations lived and their gender make-up. The most strikingly different result, that of Fenner et al., derives from a study group that was institutionalized, but this was not the case for the other two, most or all of whom, like the present cohort, lived in the community. Where gender is concerned, gender is not reported by either Fenner et al. or by Devenny et al. and the sexes were equally represented in Kittler et al.’s study (in fact a continuation of that by Devenny et al.). In the present group, they were equally represented in BPVS scores but in the vocabulary (WPPSI) test women outnumbered men at every age, at times (ages 30, 35, 40 and 45) by almost two to one. This may be seen in the context of the finding that mean scores on verbal tests of these women are markedly higher than are those of the men. For BPVSage, mean scores of the women are significantly higher at age 21 (P = 0.008) and age 30 (P = 0.03), and for expressive language (WPPSI age) at every age except 30, significance varying from 0.01 at age 40 to 0.02 at ages 45 and 47, 0.03 at age 21 and 0.05 at age 35. This verbal superiority of females with Down syndrome has been found also in other studies (Jones & Casey 1990; Sloper et al. 1990; Shepperdson 1994), and it seems likely that the stronger representation of more verbally able women in the present study has contributed to the overall stability of verbal scores in the present group, while community rather than institution placement may also have been a factor. Self-help skills declined from a maximum at age 30 by fewer than three points, and the decline was largely due to the ‘demented’ group, similar to the finding by Prasher and Filer (1995). Other indicators of the onset of dementia in this group were a decline in the ability to perform everyday domestic tasks and in independence in outdoor mobility, while health also became less good in the ‘dementing’ than in the ‘healthy’ group. Unlike findings from other research (Holland et al. 2000; Urv et al. 2008; Oliver et al. 2011), no increase was found in aggression, nor in other behavioural indicators such as crying, disorientation, sleep problems, etc. This may be because these were not, apart from aggression, specifically inquired about, but neither were they mentioned in the spontaneous comments of carers.
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Two measures, the NAID and RBMT-C, have been used in this study to detect the onset and progress of cognitive deterioration and appear to have fulfilled that purpose. Correlations (Pearson) between the two measures are high, ranging from 0.86 to 0.75, all significant at the 0.000 level. Given that there is little overlap in the content of the two tests, with only one item – orientation – common to both, this suggests that each is in its own way tapping into a similar range of skills and deficits. Currently, while two women are confirmed as suffering from dementia, this is not so securely established for the other five. It is also the case that two people who at age 45 were included in the ‘dementing’ group, at age 47, had results that suggested they should not be included in the group, and it is of course possible that further follow-up will come to a similar conclusion in the case of at least some of the current seven people. Findings on the two tests are supported by figures from the carer-assessed factors. It seems particularly striking that on ‘independence’ – the ability to move around alone outside the house – the ‘demented’ group surpassed the ‘healthy’ group at age 30, while their ability in this respect was significantly reduced in the comparison at age 47. It may be that the effect of changes in this ability could usefully be employed in future studies of cognitive deterioration. Three more such factors – domestic skills, self-help and independence – were also shown to have become significantly poorer in this group of ‘demented’ people, although, with the independence factor, they have not been identified in other studies of cognitive deterioration.
Conclusions A quarter of a century ago, it was said that the identification of dementia in ‘the mentally retarded population’ requires ‘a well-documented baseline’ adding ‘To date, such a definitive and comprehensive longitudinal study has not been conducted in a large sample of persons with Down Syndrome’ (Thase 1988). Although the author was referring principally to the, then more common, study of ‘institutionalized samples’ and would certainly have deplored the small, and diminishing, numbers in the present study, this, the present study, has been intended to provide just such a baseline. It has shown, as is usually the case, a proportion (7%) with confirmed cognitive deterioration and almost a quarter with or thought to be developing the condition, The remaining majority, those deemed ‘healthy’, also had scores on the non-verbal test and on domestic and self-help skills which declined, but only
marginally, while their ability to go out alone beyond the house was undiminished. At this stage of their lives, for them, well into middle age, their state is noticeably stable. How much longer this can be maintained, and what changes will come about with increasing age, can only be determined by further follow-up.
Acknowledgments Grateful thanks again to the Baily Thomas Fund for financial support and to Dr Eryl Bassett for yet more statistical advice. Thanks too to Peter Tilley, whose IT expertise enabled the use of figures.
Correspondence Any correspondence should be directed to Janet Carr, PhD, 2 Gaston Cottages, Little Bookham Street, Bookham, Surrey KT23 3BX, UK (e-mail: [email protected]).
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Ageing and Dementia in a Longitudinal Study of a Cohort with Down Syndrome Janet Carr* and Suzanne Collins† *Gaston Cottages formerly at St George’s Hospital, Cranmer Terrace, London SW170RE, UK; †Honorary Senior Lecturer, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
Accepted for publication 1 January 2014
Background A population sample of people with Down syndrome has been studied from infancy and has now been followed up again at age 47 years. Methods Intelligence and language skills were tested and daily living skills assessed. Memory/cognitive deterioration was examined using two test instruments. Results Scores on verbal tests of intelligence changed little. Those on a non-verbal test, on self-help skills and on both memory tests showed some decline, even when the scores of those already suffering from dementia were discounted.
Introduction That older people with Down syndrome are more vulnerable to cognitive deterioration than are either those in the general population or those whose intellectual disabilities are ascribed to other causes is now well accepted (Dalton & Crapper 1977; Burt et al. 1995). Nevertheless, it is also well established that only a proportion of people with Down syndrome, however long-lived, will suffer from the condition (Oliver et al. 1998; Silverman et al. 1998; Janicki & Dalton 2000). It becomes pertinent then to try to identify, first, the trajectory of any cognitive decline in people with Down syndrome who do not progress to dementia; and second, the factors that may distinguish those showing only the effects of normal ageing from those in the early stages of dementia. Burt et al. (1995) studied two groups of people with intellectual disabilities, one group with and another without Down syndrome, over 3–5 years. Aiming at ‘a study of typical ageing’, they excluded any who showed three or more signs of dementia, excluding almost three times as many people with Down syndrome as of those in the comparison group. Only one factor, verbal fluency, demonstrated decline unique to those with Down © 2014 John Wiley & Sons Ltd
Conclusions At age 47, scores on most tests of even the majority of the cohort (i.e. those not definitely diagnosed with dementia) showed some decline. While this includes the scores of people who may subsequently develop dementia, it may also reflect the normal ageing process in this population. Keywords: dementia, Down syndrome, longitudinal
syndrome. Older people in both groups showed declines in community living and on delayed memory. The authors comment that, while consistent with those of other research, in that difference is more likely to be found on more complex tasks, these findings should be interpreted cautiously because of the confounding of age and cohort in crosssectionalcomparisons. Devenny et al. (2000) carried out a prospective study of 44 adults with Down syndrome, using the WISC-R, which was given twice over at least 4 years, omitting the picture arrangement and similarities subtests because of baseline floor effects. Participants divided into four groups, one that remained healthy (and was on average at least 6 years younger than the other three) and three with differing degrees of dementia, characterized as ‘questionable’, ‘early’ stage and lastly ‘middle’ stage. Scores of participants in the ‘healthy’ group were distinguished from those in each stage of dementia on block design and coding; from the combined dementia groups on object assembly, picture comparison, arithmetic and comprehension; and from those in the middle stage of dementia on vocabulary and digit span. Thus, in this study, two WISC subtests, block design and coding, were the most sensitive to cognitive decline [block design having been similarly implicated by Gibson et al. (1988)]. Devenny 10.1111/jar.12093
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et al. (2000) characterize these two tests as requiring ‘perception of visual stimuli, visual organization and visuomotor coordination’ which appear to be ‘more vulnerable to decline related to dementia’. By contrast, information and vocabulary, relying on ‘semantic memory’, and digit span, relying on short-term memory, were relatively well preserved. Behavioural changes, as indications of dementia, have been identified in several studies. Holland et al. (2000) found the emergence of behavioural and personality problems preceded the findings of neurological signs, and Ball et al. (2008) found that in a pre-clinical group changes in personality or behaviour were more common than memory changes. Oliver et al. (2011), stressing that changes in behaviour are as important as are neurological signs, showed both behavioural excesses (crying, restlessness, aggression) and deficits (inactivity, disorientation, becoming lost) to occur more often in people with Down syndrome with dementia than in either an older, non-demented group or in a younger group of people with Down syndrome. Urv et al. (2008) also found an excess of maladaptive behaviours (aggression, fearfulness, sleep problems) in people with Down syndrome in the early stages of dementia while in Prasher and Filer’s (1995) study problem behaviours (not including aggression) occurred significantly more often in the demented people. A group of 30 people with Down syndrome studied by Adams and Oliver (2010) showed an increase in behavioural excesses and poorer executive function, but no significant change in adaptive skills, in those developing cognitive deterioration. Prasher and Filer, however, found a demented group to be significantly poorer in feeding and washing skills and in the occurrence of urinary incontinence than was the case with the non-demented group. In a study focussing not on the approach of dementia but on differences in the ageing process between those with and without Down syndrome, Esbenson et al. (2008) report on a longitudinal project carried on over 9 years. There were 150 people with Down syndrome and another group with intellectual disabilities due to other causes whose ages went from 19 to 68 years (mean age 36 years). Changes in health, functional abilities and behaviour problems were assessed but not cognitive ability. There was a (non-significant) ‘trend’ for the health of the Down syndrome group to decline with age, although four out of five remained in ‘excellent health’ by the end of the study, when mean age was 44 years. Bertoli et al. (2011), also not concerned with dementia, studied a large group, 518, of people with Down syndrome, ages ranging from 0 to 63 years (mean age,
calculated from data provided, 24 years) and found that while the children enjoyed a wide range of social experiences, for adults these became markedly more limited, leading to an emphasis on a routine of homebased activities. The present study was intended to provide further information on the ageing and/or dementing processes in a population of people with Down syndrome for whom longitudinal data are available.
Method A population sample of babies with Down syndrome born in 1 year (December 1963–November 1964) in one geographical area has been seen and tested by the first author at age 6 weeks and at intervals to 21 and 30 years, and then at 5 year intervals to 45 years (Carr 1975, 1995, 2000, 2003, 2012). At the most recent time, two people were confirmed, by the medical personnel involved with them, as having dementia, and six others were thought, by their carers and on the grounds of the tests used on successive occasions, to be possibly showing the early signs of the disease. All at that time were women. Following consultation with Prof. Tony Holland, it was decided to carry out the next follow-up after two rather than 5 years. Accordingly all those still available were seen at age 47. Table 1 shows the losses to the study over 47 years (from the original total of 54). Of the 30 people seen at age 45, the father of one man said he and his son no longer wished to be involved, leaving 29 participants at age 47. 21 people were seen by the first author and eight by Dr Suzanne Collins. They were given most of the same tests as had been used from age 30 years to 45 years – the Leiter International Performance Scale (LIPS), the British Picture Vocabulary Scale (BPVS), the vocabulary scale from the Wechsler Pre-School and Primary Scale of Intelligence (WPPSI); and two tests of memory/dementia, the Neurological Assessment of Dementia in Individuals with Intellectual Disability (NAID, Adams & Oliver 2010) formerly known as the Oliver & Crayton Dementia Battery and the Rivermead Behavioural Memory Test for Children (RBMT-C, Wilson & Ivani-Chalian 1995). Daily living Table 1 Number, cause and timing of losses to the study from birth to 47 years Age, before (years) Deaths Withdrew Moved, address withheld
4 8 1
21 3 1
30 2
40 4
47 4 1
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skills were assessed using the handicaps, behaviour and skills schedule (HBS, Wing 1980), scores in this case being the sums of the raw scores as set out by Wing. Tests of reading, writing and arithmetic, which had been used from age 21 to age 45, were omitted. The tests used were chosen to examine as wide a range of abilities as possible and to be accessible to as many as possible of the participants. In the case of the vocabulary test, the WISC (for older children) was attempted at age 21 but was too difficult for all but a tiny minority (five of the high achieving women) to make a score on it. It seemed out of the question to attempt the related adult Wechsler scale. The NAID and RBMT-C have been described in detail elsewhere (Carr 2003). Briefly, the NAID consists of seven subtests; three of memory – of pictures, objects and sentences of increasing length; picture identification and naming; carrying out simple requests (‘clap your hands’) and of orientation. The RBMT-C consists of eleven tests of memory – of the first and second names of a person shown in a photograph; of an object which is shown and then hidden at the start of the test, and an instruction to request another appointment, both to be recalled at the end of the test; of pictures of objects and faces; a short story and route, this including a message to be picked up and replaced, all to be recalled both immediately and after a delay; and a test of orientation for time and place. Over a third of the people still lived at home, most with a surviving parent but two each with either a brother or a sister, the remaining 64% being in charity, health or social services facilities. Over half attended a Social Education Centre; two people also attended further education courses part-time. None now was in work.
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same 29 people, from age 21 to age 47, are shown in Figure 1A, for the whole group, and for men women. Figure 1A shows that, in the whole group, mean IQs declined by nearly nine points over the 26 year period; that for the men by 3.5 points; and that for the women by over 11 points. This figures include those for the two women who at 45 were seriously affected by dementia. If these two are excluded the figures are as follows (scores for the men are unaffected) (Figure 1B). Even for those without confirmed dementia, the loss for the women from age 21 was 6.7 IQ points, (z = 2.40, P = 0.016) and for the whole group 5.1 points. This compares with a loss, at 45 years, for the whole group of 1.4 points and no loss at that time by the men (Carr 2012).
(A)
(B)
Results Except where otherwise stated, all results are given only for those people who featured at every stage of the study (i.e. those who were still in the study at age 47). Where statistical significance is indicated, all tests are two-tailed. Apart from IQs and MAs, other scores, on the NAID and RBMT-C, as well as on the self-help scale, are raw scores.
Intellectual and self-help abilities On this occasion, 2 years after the last report, changes in average scores on non-verbal ability were more apparent than they had previously been. Average IQs on the Leiter International Performance Scale, on the © 2014 John Wiley & Sons Ltd, 27, 555–563
Figure 1 (A) Leiter IQs for all, and for men and women. (B) Leiter IQs for those not diagnosed with dementia, all and women.
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In contrast to the results on non-verbal ability, for those able to score on the tests, no decline in verbal ability scores was seen. Figure 2 shows the results from the BPVS test. Following a small rise from age 21 to 30 years, scores fluctuated by 3–4 months, in both the men and the women and in the two groups combined.
Figure 3 shows scores on the WPPSI vocabulary test (expressive language). Scores for the whole group peaked at age 30 and then fluctuated, while those for the men declined somewhat, being 8.5 months below the 30-year level at both ages 40 and 47. Total scores on the self-help skills scale, from age 11 to age 47, are shown in Figure 4A. The figure shows that, from a peak at age 30, by age 47 the whole group lost 4.4 points, the men 1.6 and the
(A)
Figure 2 BPVS age (months MA) for all, and for men and women. Note: those with confirmed dementia are not included as they did not make a score at age 47.
(B)
Figure 3 WPPSI vocabulary ages (months MA) for all, and for men and women. Note: those with confirmed dementia are not included as they did not make a score at age 47.
Figure 4 (A) Total self-help skills, for all, and for men and women (maximum score = 58). (B) Total self-help skills for those not diagnosed with dementia, for all and for women (maximum score = 58). © 2014 John Wiley & Sons Ltd, 27, 555–563
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women 6.9 points. These include the figures for the two women who at 45 had been diagnosed with dementia. If these are excluded the figures are shown in Figure 4B (scores for the men are unaffected). Setting aside the scores of the two women with dementia, the loss for the whole group from age 30 was 2.3 points and that for the women 2.5 points. Results from the tests of memory/dementia, for those able to make a score on the tests, are shown in Figures 5 and 6.
Figure 5 Mean scores on the NAID, for all and for men and women.
Figures 5 and 6, which do not include scores of those confirmed with dementia, show that, from the peak figures attained at ages 35–40, the loss on the NAID, for the whole group, was 9.9 points (of the order of 14%); for the men, 8.3 points (13%); and for the women, 12.5 points (16%). For the RBMT-C, from a peak at age 40, the equivalent losses were, for the whole group, 13.1 points (30%); for the men, 7.2 points (20%); and for the women from a peak at ages 35 and 40, 19 points (38%). Thus, even for those not currently with confirmed dementia, these tests show some falling off in performance, this being shown rather more clearly by the RBMT-C than in the NAID and being more pronounced in the women; the loss for the men just fails to reach significance (z = 1.87, P = 0.060), but that for the women is significant (z = 2.44, P = 0.016). Looking at score changes for individuals: of the six women identified at age 45 as possibly showing the early signs of dementia, at 47, this was not confirmed for two; each had slightly increased scores on both tests of dementia, one also on both verbal and non-verbal intelligence, while for the other, these scores had declined somewhat. The remaining four showed marked declines on both dementia tests, of between eight and 39 points on the NAID and of between 21 and 40 points on the RBMT-C. Three also showed declines on the nonverbal test (the mother of one woman had consulted her GP about her concern regarding her daughter’s shortterm memory, but had had her worries played down by the GP who attributed these difficulties to the menopause). With one exception,1 no other member of the cohort had declines of these magnitudes on both tests. These four then are regarded as being probably in the early stages of dementia. On this most recent occasion, the scores of one man also gave rise to concern. Since age 35 (i.e. at ages 40, 45 and 47), he had been increasingly unco-operative in the test situation. His scores on the NAID were 53 and 43 at ages 40 and 45, while at age 47 it was not possible to get a response from him on the test. This has also been the case with him at all three ages on the RBMT-C. On the non-verbal IQ test, his scores declined from 53 at age 40 to 36 at age 45 and approximately 22 at age 47. In addition, his movements have become notably
1
Figure 6 Mean scores on the RBMT-C, for all, and for men and women. © 2014 John Wiley & Sons Ltd, 27, 555–563
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This is a man who, 15 months earlier, had been found to have an advanced cancer, had had extensive treatment and was given not more than 5 years to live. Although currently stable, he is ‘so tired all the time’ and all his activities are greatly restricted and reduced.
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awkward and slow. He too should now be regarded as being probably affected by dementia. With the two already diagnosed with dementia, there are now seven people in the affected, ‘dementing,’ group, to be distinguished from the remaining 22 ‘healthy’ people. The scores of these two groups, on the two tests of dementia, are shown in Figure 7. In each group, the scores are of those able to participate in the tests. Scores at age 30 on both tests were nearly 20 points higher for the ‘dementing’ group; at age 47, on the NAID, those for the ‘dementing’ group were identical to those of the ‘healthy’ group, while on the RMBT-C they were 20 points lower, although the difference is not significant. A number of other factors, implicated in other research or thought to be with the potential to be affected by the ageing process, were examined. Aggression, noted as increasing with the onset of dementia (Oliver et al. 1998; Urv et al. 2008), showed no increase in the present study population, nor in the seven with suspected/confirmed dementia. Health of the group declined slightly but not significantly, as has been shown in other studies (Esbenson et al. 2008). Vision deteriorated, 82% of the 47-year-olds compared with 50% of the 30-year-olds being said to have poor or very poor vision, but the difference is not significant. Hearing also declined, 55% being said to have normal hearing at age 47 compared with 79% at age 35, and this difference is significant (z = 2.54, P = 0.02).
Figure 7 Mean scores on the NAID and RBMT-C for ‘healthy’ and ‘dementing’ groups. For the ‘healthy’ group n = 18 throughout. For the ‘dementing’, NAID, ages 30–40, n = 7, age 45, n = 5, age 47, n = 4. RBMT-C, age 30–35, n = 7, age 40, n = 6, ages 45–47, n = 4.
Four carer-assessed variables, thought to have the possibility of distinguishing between the ‘healthy’ and the ‘dementing’ group, were examined: total self-help, domestic skills, independence – how far the person could go from the house alone - and health, at ages 30–47 years, for each of these two groups (see Figure 8). At age 30, one of the differences, that for independence, was significant, the advantage being to the ‘dementing’ group, the remainder being non-significant. At age 47, all were significant at P = 0.01–0.04, the advantage being to the ‘healthy’ group in all cases. Considering the individual items that make up the selfhelp scale (feeding, washing, dressing, toiletting), mean scores for the ‘healthy’ group declined by one point or less from age 30 to 47 while those for the ‘dementing’ group declined quite regularly over the 17 year period and were below the means for the ‘healthy’ group from age 40 onwards, but the differences do not reach significance.
Discussion The current phase of the study was carried out 2 years after the preceding one, instead of the 5 year gap that had been the case over the previous decades, due to concerns over the declining abilities of some members of the cohort. For two of these, continuing decline was not found, but was for the other six, while the scores of another at 47 led to his being included in the seven now with confirmed or suspected cognitive deterioration. This group now constitutes almost a quarter of the surviving study population. In the remaining 22, there were now some small score declines. On the non-verbal test, the loss from age 21 to age 47 was, for the ‘healthy’ group, just over five IQ points; for the men, 3.5 points; and for the women, nearly seven points, this last being statistically significant. Nevertheless, the loss remains only about a third to half of that expected of the nondisabled population over a similar period, in whom a loss of five IQ points per decade is found (Carr 2005). On verbal tests, and in contrast with the finding that, in the general population, crystallized intelligence ‘tends to maintain or improve slightly through the late 60s and, occasionally, the early 70s’ (Kaufman 1990, p;.195), in other studies of people with Down syndrome verbal ability has been seen to decline with age. These studies were carried out over varying periods, from 3 to 4 years (Burt et al. 1995) to 22 years (Haxby 1989). All showed declines, and three, covering about 7 years each, showed percentage declines of 17% (Kittler et al. 2004), 21% (Devenny et al. 2000) and 36% (Fenner et al. 1987). © 2014 John Wiley & Sons Ltd, 27, 555–563
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Figure 8 Mean scores from age 30 to age 47 on carer-assessed factors for ‘healthy’ and ‘dementing’ groups.
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Compared with these, the picture offered by the present study is different, over a similar period to that covered by the three mentioned above (age 40–47) and using the same test instrument (BPVS) mean score rose by 1%. The reason for this difference, of the present study from the three others, is not clear. Two possible reasons were considered: where the study populations lived and their gender make-up. The most strikingly different result, that of Fenner et al., derives from a study group that was institutionalized, but this was not the case for the other two, most or all of whom, like the present cohort, lived in the community. Where gender is concerned, gender is not reported by either Fenner et al. or by Devenny et al. and the sexes were equally represented in Kittler et al.’s study (in fact a continuation of that by Devenny et al.). In the present group, they were equally represented in BPVS scores but in the vocabulary (WPPSI) test women outnumbered men at every age, at times (ages 30, 35, 40 and 45) by almost two to one. This may be seen in the context of the finding that mean scores on verbal tests of these women are markedly higher than are those of the men. For BPVSage, mean scores of the women are significantly higher at age 21 (P = 0.008) and age 30 (P = 0.03), and for expressive language (WPPSI age) at every age except 30, significance varying from 0.01 at age 40 to 0.02 at ages 45 and 47, 0.03 at age 21 and 0.05 at age 35. This verbal superiority of females with Down syndrome has been found also in other studies (Jones & Casey 1990; Sloper et al. 1990; Shepperdson 1994), and it seems likely that the stronger representation of more verbally able women in the present study has contributed to the overall stability of verbal scores in the present group, while community rather than institution placement may also have been a factor. Self-help skills declined from a maximum at age 30 by fewer than three points, and the decline was largely due to the ‘demented’ group, similar to the finding by Prasher and Filer (1995). Other indicators of the onset of dementia in this group were a decline in the ability to perform everyday domestic tasks and in independence in outdoor mobility, while health also became less good in the ‘dementing’ than in the ‘healthy’ group. Unlike findings from other research (Holland et al. 2000; Urv et al. 2008; Oliver et al. 2011), no increase was found in aggression, nor in other behavioural indicators such as crying, disorientation, sleep problems, etc. This may be because these were not, apart from aggression, specifically inquired about, but neither were they mentioned in the spontaneous comments of carers.
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Two measures, the NAID and RBMT-C, have been used in this study to detect the onset and progress of cognitive deterioration and appear to have fulfilled that purpose. Correlations (Pearson) between the two measures are high, ranging from 0.86 to 0.75, all significant at the 0.000 level. Given that there is little overlap in the content of the two tests, with only one item – orientation – common to both, this suggests that each is in its own way tapping into a similar range of skills and deficits. Currently, while two women are confirmed as suffering from dementia, this is not so securely established for the other five. It is also the case that two people who at age 45 were included in the ‘dementing’ group, at age 47, had results that suggested they should not be included in the group, and it is of course possible that further follow-up will come to a similar conclusion in the case of at least some of the current seven people. Findings on the two tests are supported by figures from the carer-assessed factors. It seems particularly striking that on ‘independence’ – the ability to move around alone outside the house – the ‘demented’ group surpassed the ‘healthy’ group at age 30, while their ability in this respect was significantly reduced in the comparison at age 47. It may be that the effect of changes in this ability could usefully be employed in future studies of cognitive deterioration. Three more such factors – domestic skills, self-help and independence – were also shown to have become significantly poorer in this group of ‘demented’ people, although, with the independence factor, they have not been identified in other studies of cognitive deterioration.
Conclusions A quarter of a century ago, it was said that the identification of dementia in ‘the mentally retarded population’ requires ‘a well-documented baseline’ adding ‘To date, such a definitive and comprehensive longitudinal study has not been conducted in a large sample of persons with Down Syndrome’ (Thase 1988). Although the author was referring principally to the, then more common, study of ‘institutionalized samples’ and would certainly have deplored the small, and diminishing, numbers in the present study, this, the present study, has been intended to provide just such a baseline. It has shown, as is usually the case, a proportion (7%) with confirmed cognitive deterioration and almost a quarter with or thought to be developing the condition, The remaining majority, those deemed ‘healthy’, also had scores on the non-verbal test and on domestic and self-help skills which declined, but only
marginally, while their ability to go out alone beyond the house was undiminished. At this stage of their lives, for them, well into middle age, their state is noticeably stable. How much longer this can be maintained, and what changes will come about with increasing age, can only be determined by further follow-up.
Acknowledgments Grateful thanks again to the Baily Thomas Fund for financial support and to Dr Eryl Bassett for yet more statistical advice. Thanks too to Peter Tilley, whose IT expertise enabled the use of figures.
Correspondence Any correspondence should be directed to Janet Carr, PhD, 2 Gaston Cottages, Little Bookham Street, Bookham, Surrey KT23 3BX, UK (e-mail: [email protected]).
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