Alzheimer’s & Dementia 11 (2015) 271-279
Prevalence of dementia in urban and regional Aboriginal Australians Kylie Radforda,b,c,*, Holly A. Macka, Brian Drapera,d,e, Simon Chalkleya,f, Gail Daylightg, Robert Cumminga,h, Hayley Bennetta, Kim Delbaerea,i, Gerald A. Broea,b,j a Neuroscience Research Australia, Sydney, Australia Ageing Research Centre, Prince of Wales Hospital, Sydney, Australia c School of Medical Sciences, University of New South Wales, Sydney, Australia d Academic Department for Old Age Psychiatry, Euroa Centre, Prince of Wales Hospital, Sydney, Australia e School of Psychiatry, University of New South Wales, Sydney, Australia f St Vincent’s Clinical School, University of New South Wales, Sydney, Australia g Aboriginal Strategy & Consultation Unit, South Eastern Sydney Local Health District, Sydney, Australia h School of Public Health, University of Sydney, Sydney, Australia i School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia j Geriatric Medicine, University of New South Wales, Sydney, Australia b
Abstract
Background: This study aimed to determine the prevalence of dementia in collaboration with urban/ regional Aboriginal communities. Methods: A census of Aboriginal and Torres Strait Islander men and women aged 60 years and above in the target communities identified 546 potential participants, with 336 (61.5%) participating in this cross-sectional study. Participants completed a structured interview and cognitive screening tests. One hundred fifty-three participants also completed a detailed medical assessment. Assessment data were reviewed by a panel of clinicians who determined a diagnosis of dementia or mild cognitive impairment (MCI) according to standard criteria. Results: Crude prevalence of dementia was 13.4%, and age-standardized prevalence was 21.0%. The most common types of dementia were Alzheimer’s dementia (44%) and mixed dementia diagnoses (29%). Estimated prevalence of MCI was 17.7%. Conclusion: Consistent with previous findings in a remote population, urban and regional Aboriginal Australians face high rates of dementia at younger ages, most commonly Alzheimer’s dementia. Ó 2015 The Alzheimer’s Association. Published by Elsevier Inc. All rights reserved.
Keywords:
Indigenous population; Epidemiology of dementia; Alzheimer’s disease; Mild cognitive impairment; Vascular dementia
1. Introduction There are little data on dementia rates in the major Fourth World Indigenous people who have welldocumented differences in life expectancy, midlife disease rates, and levels of adverse social and biological risk factors compared with their First World neighbors [1].
Conflict of interest: The authors declare no conflicts of interest. *Corresponding author. Tel.: 161-2-93991269; Fax: 161-2-9399-1082. E-mail address: [email protected]
One study showed that overall prevalence of dementia was similar for an Indigenous Cree sample and a nonindigenous Canadian sample, and rates of Alzheimer’s-type dementia were relatively low in the Indigenous group [2]. In contrast, another study found a high prevalence of dementia in a remote Aboriginal Australian population relative to the nonindigenous Australian rate and most other populations worldwide [3]. These remote Aboriginal people had high rates of illiteracy, lack of formal education, and many were non-English speaking or spoke English as a second language [3]. However, the majority of Aboriginal Australians (75%) are urban and residing in cities and
1552-5260/$ - see front matter Ó 2015 The Alzheimer’s Association. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jalz.2014.03.007
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regional towns (i.e., nonremote settings) [4]. Urban Aboriginal people are predominantly English speaking, literate, and have at least basic education. Yet, similar to remote Aboriginal populations, urban Aboriginal people have high rates of midlife noncommunicable diseases, particularly cardiovascular and metabolic disorders [5], and possibly also higher dementia rates. The Koori Growing Old Well Study is investigating the epidemiology and related service needs of urban and regional dwelling Aboriginal Australians aged 60 years and over. The present analyses aimed to determine the prevalence of dementia and cognitive impairment in this urban majority of aging Aboriginal Australians and provide comparative data for further studies of dementia prevalence in disadvantaged Fourth World people.
2. Methods 2.1. Study design and setting A cross-sectional population-based survey of aging and dementia was undertaken in collaboration with local Aboriginal controlled community health organizations and local Elders across five Aboriginal communities (study sites), two in metropolitan Sydney and three on the midnorth coast of New South Wales (NSW), Australia. Aboriginal Australians make up around 2.5% of the overall urban population compared with 30% to 90% in more sparsely populated remote areas, with the state of NSW having the largest Aboriginal population. Study sites were defined by local government area boundaries, to align with Australian Bureau of Statistics (ABS) population census reporting. The sites were chosen as generally representative of the distribution of the urban Aboriginal population. A study census was conducted to identify all Aboriginal and Torres Strait Islander residents aged 60 years and older in these communities, using Aboriginal community organization lists from each site supplemented by a snowballing technique with support of local organizations, community members, and local Aboriginal researchers employed through the study. Snowballing entailed asking participants and other collaborating community members to identify potential study participants known to them, to augment and refine existing community lists. Snowball sampling is recommended in populations with incomplete and/or unavailable identification and where people are likely to know each other [6]. Snowballing continued from study initiation in September 2008 until completion of data collection (September 2012). The study design involved two phases. First, study participants completed a structured interview of their life history, general health, and well-being, as well as dementia screening tests (phase 1). Dementia screening tests included the Mini-Mental State Examination (MMSE) [7], modified Kimberley Indigenous Cognitive Assessment
(mKICA) [7], and Rowland Universal Dementia Assessment Scale (RUDAS) [8]. The mKICA was adapted for the urban setting from a validated assessment of cognition in remote Aboriginal populations [9] and is scored out of a total of 39. The RUDAS was developed to improve cognitive assessment in culturally diverse elderly populations, has been extensively validated [10,11], and is scored out of a total of 30. Predefined screening cutoffs set for this study were MMSE 26, mKICA 35, and/or RUDAS 25 [7]. Participants who scored at or below the cutoff on any one of these tests proceeded to phase 2 of the study, along with a 20% random sample of those scoring above the cutoff on all three tests. Phase 2 involved a detailed 90-minute medical and cognitive assessment with a geriatrician or physician with expertise in aging and dementia, as well as a contact person (CP) interview with a relative or friend nominated by the participant. CP interviews mirrored phase 1 participant interviews. Phase 2 assessments were completed blind to all phase 1 data. Median time between phase 1 and 2 assessments was 3 months (interquartile range, 1–7 months). The study design is depicted in Fig. 1, and full details of these study assessments have been reported elsewhere [7]. The study was approved by the Aboriginal Health and Medical Research Council (AHMRC; 615/07), the University of New South Wales Human Research Ethics Committee (HREC 08003), and NSW Population & Health Services Research Ethics Committee (AU RED Ref: HREC/09/CIPHS/65; Cancer Institute NSW Ref: 2009/ 10/187). 2.2. Participants Participation was available to all eligible Aboriginal and Torres Strait Islander men and women identified through our census process. Inclusion criteria were Aboriginal and/or Torres Strait Islander identification, age 60 years and older at the time of study enrollment, and residing in the study site for at least 6 months. Exclusion criteria included current incarceration and stroke within the past 3 months. All participants gave written informed consent or, in cases when capacity to consent was lacking, gave verbal assent and written informed consent was obtained from an appropriate relative or a caregiver. Study participants were also asked to nominate a CP to complete phase 2 assessments. CPs were not necessarily Aboriginal and also provided written informed consent to participate in the study. The target sample size of 366 Aboriginal and Torres Strait Islander people aged 60 years and older was calculated based on a 60% participation rate of the total population within our catchment areas (n 5 609 from ABS population data) and a 95% probability that a sample estimate between 19.6% and 28.4% would be obtained if the true dementia prevalence rate mirrored that found in remote communities (i.e., 23.8%).
K. Radford et al. / Alzheimer’s & Dementia 11 (2015) 271-279
CENSUS LIST N=823
273
Excluded: N=280 34 Not Aboriginal or TSI 37 Too young 61 Died 144 Not living in area 4 Incarcerated
CENSUS ELIGIBLE N=546
PHASE 1: Participant Interview N=336
Screened Positive (Pos) N=171
Non-participation: N=210 125 Refused 31 Unable to contact 10 Moved away before interviewed 9 Died before interviewed 35 Unable to schedule*
Screened Negative (Neg) N=165
20% randomly selected N=33
80% end study participation N=132
Non-participation: Pos N=44 32 2 6
Neg N=7 7 -
Medical Refused Lost to follow-up Died *
Unable to schedule 4 N=75 Contact Person (CP) N=15 40 Participant refused CP 5 10 No CP available 1 12 CP refused 4 5 Unable to contact CP 5 1 Participant died 7
*
Unable to schedule
PHASE 2: Medical Assessment (N=127) CP Interview (N=96)
1 PHASE 2: Medical Assessment (N=26) CP Interview (N=18)
Case reviewed by consensus panel for diagnosis N=153
Fig. 1. Study flow diagram. *Unable to schedule interview before the end of data collection (September 30, 2012). TSI, Torres Strait Islander.
2.3. Outcomes Phase 2 medical assessment data were reviewed by a panel of three or more clinicians including at least one geriatrician and one clinical neuropsychologist. This panel made consensus determinations of cognitive impairment, dementia, and dementia type according to standard diagnostic criteria [12–16]. These included “all-cause” dementia [14], Alzheimer’s dementia (AD) [12,14], vascular dementia [12], dementia with Lewy bodies [13],
frontotemporal dementia [15], dementia due to the persisting effect of substance abuse [12], dementia due to other medical conditions [12], and mild cognitive impairment (MCI) [16]. 2.4. Statistical analysis Data were analyzed using IBM SPSS Statistics software (IBM, Armonk, NY, USA; version 21) and Microsoft Excel 2010 (Redmond, WA, USA). We
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determined crude and age-standardized prevalence rates for all-cause dementia, given the relatively young age of our study population relative to the general Australian population. Age standardization was calculated using a direct method [17] with reference to current Australian population estimates of dementia and age distribution for those aged 60 years and older [18]. The prevalence of dementia and MCI in the 20% random sample of high-scoring (screened negative) participants was inverse weighted to the full sample of high scorers. For 51 participants who were selected for phase 2, but did not complete a medical assessment (or consensus diagnosis), we based dementia diagnosis on a phase 1 MMSE score ,22 (to give 95% specificity in this population, as determined by preliminary analyses) [19] combined with any evidence of functional impairment [20]. Confidence intervals (CIs) were calculated using the asymptotic method with continuity correction [21] for crude rates and Chiang Poisson approximation method [22] for standardized rates. We also examined a range of demographic and clinical variables in our sample and used Pearson chi-square tests to compare men and women on these variables. Missing self-report data were imputed using CP responses where available.
3. Results 3.1. Participants The study census identified 546 eligible participants across the five study sites, which compared well with our reference figure of 609 Aboriginal or Torres Strait Islander people, based on available population statistics during the study (ABS, 2006). Of these, 336 (61.5%) participated in the study, aged 60 to 92 years (M 5 66.6 years, standard deviation [SD] 5 6.3 years). Reasons for exclusion or nonparticipation at each stage of the study are shown in the study flow diagram (Fig. 1). Participants did not differ significantly from eligible nonparticipants in terms of age, sex, or urban/regional distribution [7]. As detailed in Table 1, participants were predominantly Aboriginal (99.4%), female (59.5%), aged younger than 70 years (72.9%), and with some formal education (99.1%). All participants spoke English, typically as their first language (98.2%). Compared with women, men had significantly (P , .05) higher rates of head injury, heavy alcohol use, and prior prison/police custody and were more likely to have been in paid employment through their lifetime and to be currently married or in a de facto relationship. Women were more likely (P , .05) to have achieved at least 10 years of education, to be widowed or divorced, and to have had a fall in the past year. These results are shown in Tables 1 and 2. Based on phase 1 screening, 204 participants were selected to continue to study phase 2 (see Fig. 1). For
selected participants, there were no significant differences in age, sex, or MMSE scores between those who did (n 5 153) and did not (n 5 51) complete phase 2 medical/ cognitive assessments. One hundred fourteen CPs also participated. CPs were aged 23 to 82 years (M 5 52.3 years, SD 5 11.7 years), 71.9% (n 5 82) female, commonly the daughter (n 5 38; 33.3%) or spouse (n 5 27; 23.7%) of the participant, currently (n 5 48; 42.1%) or previously (n 5 38; 33.3%) lived with the participant, typically saw the participant daily (n 5 68; 59.6%), and reported knowing them well or very well (n 5 112; 98.2%). 3.2. Outcomes Of the 153 cases reviewed by the consensus panel, 41 cases of dementia and 38 cases of MCI were diagnosed. For dementia cases, 17 were classified as mild, 12 as moderate, and 12 as severe [23]. A further four cases of cognitive impairment were identified, related to chronic schizophrenia (n 5 2), developmental disorder (n 5 1), or delirium due to a general medical condition (n 5 1). There were no cases of dementia in the 20% randomly selected group of those with a negative phase 1 screening result (n 5 26), but four cases of MCI were identified in this group. Thus, prevalence of MCI was prorated for the remaining 139 participants with a negative screening result who did not complete a phase 2 medical assessment. Analysis of the 51 participants who were assigned to phase 2, but did not complete a medical assessment revealed four additional cases of dementia (two had refused a medical assessment and two had died), according to predefined criteria (described previously). Thus, the crude dementia prevalence rate was 13.4% (95% CI, 9.6–17.2) and the age-standardized rate was 21.0% (95% CI, 12.8–29.2). Fig. 2 shows dementia prevalence at different ages in the present study compared with a previous study in a remote Aboriginal population [3] and official estimates for the general Australian population (based on meta-analysis of data from Australia, Europe, and the United States) [18]. Prevalence of MCI was 17.7% (95% CI, 13.4–21.9). The total burden of cognitive impairment (including dementia, MCI, and other cognitive disorders) was 32.3% in this population. As depicted in Fig. 3, AD was the most common diagnosis of dementia, with 18 (43.9%) cases of probable AD. Other diagnoses of dementia included vascular dementia (n 5 7; 17.1%), dementia due to head trauma (n 5 3; 7.3%), and frontotemporal dementia (n 5 1; 2.4%). There were a further 12 cases (29.3%) with mixed dementia diagnoses. 4. Discussion The prevalence of dementia in the present urban/regional Aboriginal Australian population was comparable with rates found in a remote population at ages 60 years and older
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Table 1 Characteristics of sample on key demographic and social variables Total, n 5 336 Variable Indigenous status Aboriginal TSI Aboriginal and TSI Age group, y 60–69 70–79 801 Education ,10 y school 10 y education Basic literacy* Current residence Urban (Sydney) Regional (other NSW) Local area .20 yy Residential aged care Living alonez Marital status Married/de facto Widowed/divorced Never married Employment Currently employed Ever employed Main job, unskilledx Prison/police custody (past) Early life (birth to 15 years old) Residence Major city Regional/rural Remote Family stress One parent died Both parents died Removed from family Poor health{
N
%
328 2 6
98 1 2
245 77 14
Men, n 5 136 Missing data
Women, n 5 200
N
%
Missing data
N
%
Missing data
0 0 0
133 1 2
98 1 1
0 0 0
195 1 4
98 1 2
0 0 0
73 23 4
0 0 0
94 37 5
69 27 4
0 0 0
151 40 9
76 20 5
0 0 0
204 131 325
61 39 97
1 1 1
93 43 130
68 32 96
0 0 0
111 88 195
56 44 98
1 1 1
140 196 254 17 72
42 58 76 5 23
0 0 0 0 9
51 85 103 8 34
38 63 76 6 27
0 0 0 0 3
89 111 151 9 38
45 56 76 5 21
0 0 0 0 6
124 166 39
38 50 12
7 7 7
64 54 16
48 40 12
2 2 2
60 112 23
31 57 12
5 5 5
64 317 118 109
19 95 37 34
4 4 4 13
31 133 55 74
23 99 41 56
2 2 1 4
33 184 63 35
17 93 35 18
2 2 3 9
103 216 15
31 65 4
2 2 2
44 89 3
32 65 2
0 0 0
59 127 12
30 64 6
2 2 2
69 5 33 78
21 1 10 24
2 2 9 5
30 2 11 28
22 1 8 21
0 0 3 2
39 3 22 50
20 2 11 25
2 2 6 3
Abbreviations: TSI, Torres Strait Islander; NSW, New South Wales. *Adequate for Mini-Mental State Examination assessment. y Residing in the study catchment area for more than 20 years. z Excludes those living in residential aged care facilities. x Excludes those never employed, unskilled work includes laborers, cleaners, factory workers, etc. { Childhood health self-rated as poor/fair (vs. good/very good/excellent).
(23.8%; total n 5 168) [3]. The standardized rate of 21.0% is substantially (threefold) higher than the overall Australian population prevalence of 6.8% in this age range [18]. Consistent with previous studies in First World populations [24,25], our results showed that AD was most common (44% of cases), followed by vascular dementia (17% of cases). This pattern is highly similar to a population-based study of Australians aged 75 years and older [25], which found 43% of dementia cases were AD, 13% were vascular, and 30% were mixed. A similar pattern was also seen in remote Aboriginal communities [3]. In contrast to previously held opinion [26] and consistent with findings in remote Aboriginal communities [3],
dementia due to alcohol abuse was relatively uncommon in our urban population of older Aboriginal Australians. However, complex etiologies were frequently observed with close to a third of cases (n 5 12) meeting criteria for multiple types of dementia. Again, Alzheimer’s type presentations were common (i.e., possible AD)—a feature in nine (75%) of these mixed presentations. Dementia related to vascular pathology (n 5 7; 58%), head trauma (n 5 6; 50%), and alcohol abuse (n 5 4; 33%) were other key contributing factors in this mixed dementia group. Irrespective of diagnosis, our study showed high rates of stroke, head injury, and epilepsy, factors that were associated with dementia in the remote Aboriginal population [3].
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Table 2 Characteristics of sample on key medical and clinical variables Total, n 5 336
Men, n 5 136
Women, n 5 200
Variable
N
%
Missing data
N
%
Missing data
N
%
Missing data
Dementia Depression (lifetime) Anxiety (lifetime) Heavy alcohol (current)* Heavy alcohol (past)* Smoking (current) Hypertension Heart problems Stroke/TIA Diabetes Cancer Epilepsy Head injuryy Falls (past year) Hospital (past year) Disabilityz
45 114 95 65 168 86 205 140 78 144 40 25 95 78 132 166
13 35 29 20 52 26 63 43 24 44 12 8 29 24 41 51
0 11 11 11 14 11 12 10 10 9 11 13 10 11 14 11
24 39 31 39 93 36 80 61 31 54 15 6 56 23 60 59
18 29 23 29 70 27 60 46 23 40 11 5 42 17 45 45
0 3 3 3 4 3 3 3 2 2 4 5 3 4 3 5
21 75 64 26 75 50 125 79 47 90 25 19 39 55 72 107
11 39 33 14 39 26 65 41 24 47 13 10 20 28 38 55
0 8 8 8 10 8 9 7 8 7 7 8 7 7 11 6
Abbreviation: TIA, transient ischemic attack. *Measured by the Alcohol Use Disorder Identification Test – alcohol consumption questions (AUDIT-C) [37]. Heavy alcohol use defined as AUDIT-C 4. y Any head injury with loss of consciousness. z Some impairment of activities of daily living [20].
In contrast, lack of formal education was rare at just 1% of the present sample compared with 40% in remote Aboriginal people, where it was associated with dementia [3]. No significant difference in the dementia rate was found between men and women. The present study achieved recruitment of just over the targeted 60% of a population that was difficult to identify. This was due to the relatively small proportion of the total population within a given catchment area (i.e., 1.5%–11.1% across sites) and the absence of a formal registry of Aboriginal Australians. Although the sample size is lower than major dementia prevalence studies, such as the 10/66 Study [27], the present study is the largest population-based study of dementia to date for Aboriginal Australians in this age range (i.e., twice that of a previous 60
Prevalence rate (%)
50 40 Urban/regional
30
Remote
20
All Australia
10 0
60-69
70-79
80+
Age group (years)
Fig. 2. Dementia prevalence by age group: compares the current urban/ regional Aboriginal Australian population with a remote Aboriginal population (Smith et al. [3]) and the general Australian population (population projections based on data from Australia, Europe, and the United States, published by the Australian Institute of Health and Welfare, 2012 [18]).
study) [3]. The sample size, participation rate, and rate of progression/retention to phase 2 medical assessment and formal dementia diagnosis (75% of those screened/selected) were acceptable [24]. As opposed to the 10/66 single-phase approach (which avoids any such attrition), our study design allowed for a “gold standard” medical assessment with diagnosis by clinical consensus, adding to the validity of our results. We acknowledge it is possible that we missed some potential participants through our census process because of the limits of the snowballing technique. For example, Aboriginal people living within an area may not have been known to the local community or Aboriginal controlled services, particularly in city sites. Our additional recruitment technique through mainstream health services was only partly successful because of the inaccurate or incomplete records of the Indigenous status held by such services. Moreover, given that part of our recruitment approach was directed through primary health services, it is possible that our sample could have been biased to those who were sicker or who were more likely to be experiencing cognitive impairment; however, subsequent snowballing was carried out by our independent Aboriginal researchers. We also identified and recruited relatively few people in residential aged care facilities, which contributed significant dementia numbers in a previous study [3]. Limited evidence regarding the validity of cognitive measures and normative reference criteria in our study population made it challenging to diagnose MCI and subtle cognitive impairment. The present study further aims to validate and compare selected cognitive screening tests in this population, whereas a longitudinal follow-up will explore the progression rate of MCI to dementia. Clinical
K. Radford et al. / Alzheimer’s & Dementia 11 (2015) 271-279
Fig. 3. Frequency of dementia types diagnosed, by clinical consensus according to formal dementia criteria [12–15], of 41 cases in the current urban/regional Aboriginal Australian population.
examination with subsequent consensus diagnosis remains uncertain in a population with multiple potential risk factors and without the availability of normative reference criteria, neuroimaging, or an autopsy sample. Consideration of genetic risk factors, particularly apolipoprotein E polymorphisms [28], is also important. The use of genetic and biomarker research technologies in Aboriginal populations raises several historical and cultural challenges. Nonetheless, these should be explored as options for future work in close consultation and collaboration with Aboriginal communities to ensure an equitable high standard of research. However, as found in the United States [29], modifiable social and healthrelated risk factors are likely to have a bigger impact than genetic risk in accounting for differences in dementia between Aboriginal and nonindigenous Australians. The question now remains as to why there are much higher rates of dementia in older urban Aboriginal Australians compared with many other populations worldwide. The potential risk factors for cognitive decline and dementia in this population are multiple and varied. A range of factors across the life course could be contributing, directly and indirectly, to high dementia prevalence. It is likely that both early life environmental factors (e.g., low education levels, low socioeconomic status, trauma, and other adverse events) [29–31] and mid–late life biomedical factors (e.g., vascular and metabolic risk, prior head injury) [29] are driving these higher dementia rates that are common to remote and urban Aboriginal populations. In socioeconomically disadvantaged populations (including ethnic minorities and Fourth World Indigenous people), low education and illiteracy have been frequently identified as important factors linked to increased dementia risk [3,29,31–33] Although almost our entire urban sample had received some schooling and demonstrated basic literacy, the level of education in the urban Aboriginal population is considerably lower than in other older Australians; 61% of Australians aged 65 years and over have achieved 10 years of education or more [34] compared
277
with 19% in the present sample. In addition, we are examining the influence of education quality (e.g., attendance, learning disabilities, parental attitudes, and discrimination within the education system) and informal educational opportunities (i.e., enriched learning environment beyond school) on cognitive decline and dementia. Disparately high prevalence of cardiovascular diseases and diabetes mellitus in many disadvantaged populations has also been associated with greater rates of dementia [2,3,29]. An excess burden of vascular and metabolic diseases (risk factors) is apparent in Aboriginal Australians [5], and these were common in our sample. There could also be other, less obvious but nonetheless pervasive, risk factors influencing cognitive decline and higher dementia rates in this population, including early life stress [35] and head trauma [3,36]. We are planning further analysis of the present data set, coupled with longitudinal follow-up, which will help to understand these risk factors. Acknowledgments The Koori Growing Old Well Study (KGOWS) is a collaboration between Neuroscience Research Australia (NeuRA), University of NSW, and Aboriginal and academic research partners. Our collaborators include our Aboriginal partner communities, Aboriginal health managers in NSW Area Health Services (Gail Daylight, Vicki Wade, and Tim Agius), Muru Marri Indigenous Health Unit UNSW, Dementia Collaborative Research Centres, Prince of Wales Hospital, KICA Research Group at University of Western Australia, ARC-NHMRC Ageing Well Network, and the National Aboriginal and Torres Strait Islander Dementia Advisory Group at Alzheimer’s Australia. This work relied on the assistance and support of many individuals and organizations. The authors are particularly grateful to our participants; our local Elder guidance groups, KGOWS Aboriginal Reference Group; and our Aboriginal community partners who continue to offer their support for our research: Durri Aboriginal Corporation Medical Service and Booroongen Djugun in Kempsey, Darrimba Maarra Aboriginal Health Clinic in Nambucca, Galambila Aboriginal Health Service in Coffs Harbour, La Perouse Local Aboriginal Land Council, La Perouse Aboriginal Community Health Centre, and Tharawal Aboriginal Corporation in Campbelltown. We wish to recognize the hard work of our research team including Aboriginal research assistants (Bridget Jarrett, Gail Ling, Garth Fatnowna, Heidi Sainsbury, Margaret Anderson, Mervyn Davison, Michele Stewart, Sue Hoskins, and Sue Parsons), project officers and interviewers (Cecilia Minogue, Christine Metusela, Emily Hindman, Emma Schofield, Jennifer Japhet, Jennifer Sperring, Kristen Holdsworth, Lea Williams, Natalie Johnson, Rachelle Arkles, Renee Ward, and Wendy Hampshire), medical doctors (Anthony French, Brenda McPhee, Matthew Kinchington, Tabitha Hartwell, and
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William Brooks), and administrative support (Hamish Robertson, Jan Koh, and Sandra Forster). We also acknowledge Professor Lisa Jackson Pulver for her contribution to the study design and Associate Professor Emeritus David Grayson for his contribution to the design and initial implementation of the study and ongoing advice regarding data management and analyses. Funding sources: This study was supported by an Australian National Health and Medical Research Council Project Grant (510347). Initial piloting was funded by the Dementia Collaborative Research Centres (IPW02) and Alzheimer’s Australia Research. The project also received donations via the Ageing Research Centre at Prince of Wales Hospital, Sydney. K.R. is funded by the RW & JG Postdoctoral Fellowship in Aboriginal Health and Ageing.
RESEARCH IN CONTEXT
1. Systematic review: We searched OVID and MEDLINE databases for studies of dementia prevalence in the major Fourth World Indigenous people (i.e., from Canada, United States, New Zealand, and Australia), identifying only two previous cross-sectional studies [2,3]. 2. Interpretation: There is a major lack of epidemiologic data on dementia in these Fourth World Indigenous populations. The present results are comparable with findings in a remote Aboriginal population [3] and provide further evidence that Aboriginal Australians experience some of the highest rates of dementia reported worldwide. 3. Future directions: Alzheimer’s disease dementia was common, but high rates of other potential causes or risks factors for dementia (e.g., vascular, head trauma) were also observed. Longitudinal research, in addition to neuroimaging and genetic data, is needed to understand the social and biomedical risk factors contributing to the high dementia rates in urban, regional, and remote Aboriginal Australians.
References [1] United Nations. State of the world’s Indigenous peoples. New York: United Nations; 2009. [2] Hendrie HC, Hall KS, Pillay N, Rodgers D, Prince C, Norton J, et al. Alzheimer’s disease is rare in Cree. Int Psychogeriatr 1993; 5:5–14. [3] Smith K, Flicker L, Lautenschlager NT, Almeida OP, Atkinson D, Dwyer A, et al. High prevalence of dementia and cognitive impairment in Indigenous Australians. Neurology 2008;71:1470–3.
[4] Australian Bureau of Statistics, Experimental estimates and projections, Aboriginal and Torres Strait Islander Australians (Report No. 3238.0). 2009, Canberra. [5] Vos T, Barker B, Begg S, Stanley L, Lopez AD. Burden of disease and injury in Aboriginal and Torres Strait Islander peoples: the Indigenous health gap. Int J Epidemiol 2009;38:470–7. [6] Kalton G, Anderson DW. Sampling rare populations. Journal of the Royal Statistical Society Series a-Statistics in Society 1986;149:65–82. [7] Radford K, Mack HA, Robertson H, Draper B, Chalkley S, Daylight G, et al. The Koori Growing Old Well Study: investigating aging and dementia in urban Aboriginal Australians. Int Psychogeriatr 2014; 26:1033–43. [8] Storey JE, Rowland JT, Basic D, Conforti DA, Dickson HG. The Rowland Universal Dementia Assessment Scale (RUDAS): a multicultural cognitive assessment scale. Int Psychogeriatr 2004;16:13–31. [9] LoGiudice D, Smith K, Thomas J, Lautenschlager NT, Almeida OP, Atkinson D, et al. Kimberley Indigenous Cognitive Assessment tool (KICA): development of a cognitive assessment tool for older Indigenous Australians. Int Psychogeriatr 2006;18:269–80. [10] Basic D, Rowland JT, Conforti DA, Vrantsidis F, Hill K, LoGiudice D, et al. The validity of the Rowland Universal Dementia Assessment Scale (RUDAS) in a multicultural cohort of community-dwelling older persons with early dementia. Alzheimer Dis Assoc Disord 2009; 23:124–9. [11] Nielsen TR, Vogel A, Gade A, Waldemar G. Cognitive testing in non-demented Turkish immigrants—comparison of the RUDAS and the MMSE. Scand J Psychol 2012;53:455–60. [12] American Psychiatric Association, Diagnostic and statistical manual of mental disorders: DSM-IV-TR. 4th (Text Revision) ed. 2000, Washington, DC, American Psychiatric Association. [13] McKeith IG, Dickson DW, Lowe J, Emre M, O’Brien JT, Feldman H, et al. Diagnosis and management of dementia with Lewy bodies: third report of the DLB Consortium. Neurology 2005;65:1863–72. [14] McKhann GM, Knopman DS, Chertkow H, Hyman BT, Jack CR Jr, Kawas CH, et al. The diagnosis of dementia due to Alzheimer’s disease: recommendations from the National Institute on AgingAlzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimers Dement 2011;7:263–9. [15] Neary D, Snowden JS, Gustafson L, Passant U, Stuss D, Black S, et al. Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria. Neurology 1998;51:1546–54. [16] Winblad B, Palmer K, Kivipelto M, Jelic V, Fratiglioni L, Wahlund LO, et al. Mild cognitive impairment—beyond controversies, towards a consensus: report of the International Working Group on Mild Cognitive Impairment. J Int Med 2004;256:240–6. [17] Australian Institute of Health and Welfare. Age-standardised rate. Metadata Online Registry (METeOR) 2005 [cited 2012 7 May]; Available from: http://meteor.aihw.gov.au/content/index.phtml/item Id/327276. [18] Australian Institute of Health and Welfare. Dementia in Australia. Canberra: AIHW; 2012. [19] Radford K, Mack HA, Chalkley S, Draper B, Cumming R, Hoskins S, et al. Cognitive screening for dementia assessment in urban Aboriginal Australians: which test is best?. Canberra, Australia: National Dementia Research Forum; 2012. [20] Akhtar AJ, et al. Disability and dependence in the elderly at home. Age and Ageing 1973;2:102–11. [21] Blyth CR, Still HA. Binomial confidence-intervals. J Am Stat Assoc 1983;78:108–16. [22] Armitage P, Berry G. Statistical methods in medical research. 3rd ed. , Oxford: Blackwell; 1994. [23] American Psychiatric Association. Diagnostic and statistical manual of mental disorders: DSM-III-R. 3rd. , Washington, DC: American Psychiatric Association; 1987. Revised. [24] Lobo A, Launer LJ, Fratiglioni L, Andersen K, Di Carlo A, Breteler MM, et al. Prevalence of dementia and major subtypes in Europe: a collaborative study of population-based cohorts.
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[32] Afgin AE, Massarwa M, Schechtman E, Israeli-Korn SD, Strugatsky R, Abuful A, et al. High prevalence of mild cognitive impairment and Alzheimer’s disease in Arabic villages in northern Israel: impact of gender and education. J Alzheimers Dis 2012; 29:431–9. [33] Prince M, Acosta D, Ferri CP, Guerra M, Huang Y, Llibre Rodriguez JJ, et al. Dementia incidence and mortality in middleincome countries, and associations with indicators of cognitive reserve: a 10/66 Dementia Research Group population-based cohort study. Lancet 2012;380:50–8. [34] Australian Bureau of Statistics. Who are Australia’s older people? 2071.0-reflecting a nation: stories from the 2011 Census, 2012– 2013 2012; Available at: http://www.abs.gov.au/ausstats/[email protected]/ Lookup/2071.0main1features752012-2013. Accessed February 3, 2014. [35] Ritchie K, Jaussent I, Stewart R, Dupuy AM, Courtet P, Malafosse A, et al. Adverse childhood environment and late-life cognitive functioning. Int J Geriatr Psychiatry 2011;26:503–10. [36] Moretti L, Cristofori I, Weaver SM, Chau A, Portelli JN, Grafman J. Cognitive decline in older adults with a history of traumatic brain injury. Lancet Neurol 2012;11:1103–12. [37] Bush K, Kivlahan DR, McDonell MB, Fihn SD, Bradley KA. The AUDIT alcohol consumption questions (AUDIT-C): an effective brief screening test for problem drinking. Ambulatory Care Quality Improvement Project (ACQUIP). Alcohol Use Disorders Identification Test. Arch Intern Med 1998;158:1789–95.
Prevalence of dementia in urban and regional Aboriginal Australians Kylie Radforda,b,c,*, Holly A. Macka, Brian Drapera,d,e, Simon Chalkleya,f, Gail Daylightg, Robert Cumminga,h, Hayley Bennetta, Kim Delbaerea,i, Gerald A. Broea,b,j a Neuroscience Research Australia, Sydney, Australia Ageing Research Centre, Prince of Wales Hospital, Sydney, Australia c School of Medical Sciences, University of New South Wales, Sydney, Australia d Academic Department for Old Age Psychiatry, Euroa Centre, Prince of Wales Hospital, Sydney, Australia e School of Psychiatry, University of New South Wales, Sydney, Australia f St Vincent’s Clinical School, University of New South Wales, Sydney, Australia g Aboriginal Strategy & Consultation Unit, South Eastern Sydney Local Health District, Sydney, Australia h School of Public Health, University of Sydney, Sydney, Australia i School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia j Geriatric Medicine, University of New South Wales, Sydney, Australia b
Abstract
Background: This study aimed to determine the prevalence of dementia in collaboration with urban/ regional Aboriginal communities. Methods: A census of Aboriginal and Torres Strait Islander men and women aged 60 years and above in the target communities identified 546 potential participants, with 336 (61.5%) participating in this cross-sectional study. Participants completed a structured interview and cognitive screening tests. One hundred fifty-three participants also completed a detailed medical assessment. Assessment data were reviewed by a panel of clinicians who determined a diagnosis of dementia or mild cognitive impairment (MCI) according to standard criteria. Results: Crude prevalence of dementia was 13.4%, and age-standardized prevalence was 21.0%. The most common types of dementia were Alzheimer’s dementia (44%) and mixed dementia diagnoses (29%). Estimated prevalence of MCI was 17.7%. Conclusion: Consistent with previous findings in a remote population, urban and regional Aboriginal Australians face high rates of dementia at younger ages, most commonly Alzheimer’s dementia. Ó 2015 The Alzheimer’s Association. Published by Elsevier Inc. All rights reserved.
Keywords:
Indigenous population; Epidemiology of dementia; Alzheimer’s disease; Mild cognitive impairment; Vascular dementia
1. Introduction There are little data on dementia rates in the major Fourth World Indigenous people who have welldocumented differences in life expectancy, midlife disease rates, and levels of adverse social and biological risk factors compared with their First World neighbors [1].
Conflict of interest: The authors declare no conflicts of interest. *Corresponding author. Tel.: 161-2-93991269; Fax: 161-2-9399-1082. E-mail address: [email protected]
One study showed that overall prevalence of dementia was similar for an Indigenous Cree sample and a nonindigenous Canadian sample, and rates of Alzheimer’s-type dementia were relatively low in the Indigenous group [2]. In contrast, another study found a high prevalence of dementia in a remote Aboriginal Australian population relative to the nonindigenous Australian rate and most other populations worldwide [3]. These remote Aboriginal people had high rates of illiteracy, lack of formal education, and many were non-English speaking or spoke English as a second language [3]. However, the majority of Aboriginal Australians (75%) are urban and residing in cities and
1552-5260/$ - see front matter Ó 2015 The Alzheimer’s Association. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jalz.2014.03.007
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regional towns (i.e., nonremote settings) [4]. Urban Aboriginal people are predominantly English speaking, literate, and have at least basic education. Yet, similar to remote Aboriginal populations, urban Aboriginal people have high rates of midlife noncommunicable diseases, particularly cardiovascular and metabolic disorders [5], and possibly also higher dementia rates. The Koori Growing Old Well Study is investigating the epidemiology and related service needs of urban and regional dwelling Aboriginal Australians aged 60 years and over. The present analyses aimed to determine the prevalence of dementia and cognitive impairment in this urban majority of aging Aboriginal Australians and provide comparative data for further studies of dementia prevalence in disadvantaged Fourth World people.
2. Methods 2.1. Study design and setting A cross-sectional population-based survey of aging and dementia was undertaken in collaboration with local Aboriginal controlled community health organizations and local Elders across five Aboriginal communities (study sites), two in metropolitan Sydney and three on the midnorth coast of New South Wales (NSW), Australia. Aboriginal Australians make up around 2.5% of the overall urban population compared with 30% to 90% in more sparsely populated remote areas, with the state of NSW having the largest Aboriginal population. Study sites were defined by local government area boundaries, to align with Australian Bureau of Statistics (ABS) population census reporting. The sites were chosen as generally representative of the distribution of the urban Aboriginal population. A study census was conducted to identify all Aboriginal and Torres Strait Islander residents aged 60 years and older in these communities, using Aboriginal community organization lists from each site supplemented by a snowballing technique with support of local organizations, community members, and local Aboriginal researchers employed through the study. Snowballing entailed asking participants and other collaborating community members to identify potential study participants known to them, to augment and refine existing community lists. Snowball sampling is recommended in populations with incomplete and/or unavailable identification and where people are likely to know each other [6]. Snowballing continued from study initiation in September 2008 until completion of data collection (September 2012). The study design involved two phases. First, study participants completed a structured interview of their life history, general health, and well-being, as well as dementia screening tests (phase 1). Dementia screening tests included the Mini-Mental State Examination (MMSE) [7], modified Kimberley Indigenous Cognitive Assessment
(mKICA) [7], and Rowland Universal Dementia Assessment Scale (RUDAS) [8]. The mKICA was adapted for the urban setting from a validated assessment of cognition in remote Aboriginal populations [9] and is scored out of a total of 39. The RUDAS was developed to improve cognitive assessment in culturally diverse elderly populations, has been extensively validated [10,11], and is scored out of a total of 30. Predefined screening cutoffs set for this study were MMSE 26, mKICA 35, and/or RUDAS 25 [7]. Participants who scored at or below the cutoff on any one of these tests proceeded to phase 2 of the study, along with a 20% random sample of those scoring above the cutoff on all three tests. Phase 2 involved a detailed 90-minute medical and cognitive assessment with a geriatrician or physician with expertise in aging and dementia, as well as a contact person (CP) interview with a relative or friend nominated by the participant. CP interviews mirrored phase 1 participant interviews. Phase 2 assessments were completed blind to all phase 1 data. Median time between phase 1 and 2 assessments was 3 months (interquartile range, 1–7 months). The study design is depicted in Fig. 1, and full details of these study assessments have been reported elsewhere [7]. The study was approved by the Aboriginal Health and Medical Research Council (AHMRC; 615/07), the University of New South Wales Human Research Ethics Committee (HREC 08003), and NSW Population & Health Services Research Ethics Committee (AU RED Ref: HREC/09/CIPHS/65; Cancer Institute NSW Ref: 2009/ 10/187). 2.2. Participants Participation was available to all eligible Aboriginal and Torres Strait Islander men and women identified through our census process. Inclusion criteria were Aboriginal and/or Torres Strait Islander identification, age 60 years and older at the time of study enrollment, and residing in the study site for at least 6 months. Exclusion criteria included current incarceration and stroke within the past 3 months. All participants gave written informed consent or, in cases when capacity to consent was lacking, gave verbal assent and written informed consent was obtained from an appropriate relative or a caregiver. Study participants were also asked to nominate a CP to complete phase 2 assessments. CPs were not necessarily Aboriginal and also provided written informed consent to participate in the study. The target sample size of 366 Aboriginal and Torres Strait Islander people aged 60 years and older was calculated based on a 60% participation rate of the total population within our catchment areas (n 5 609 from ABS population data) and a 95% probability that a sample estimate between 19.6% and 28.4% would be obtained if the true dementia prevalence rate mirrored that found in remote communities (i.e., 23.8%).
K. Radford et al. / Alzheimer’s & Dementia 11 (2015) 271-279
CENSUS LIST N=823
273
Excluded: N=280 34 Not Aboriginal or TSI 37 Too young 61 Died 144 Not living in area 4 Incarcerated
CENSUS ELIGIBLE N=546
PHASE 1: Participant Interview N=336
Screened Positive (Pos) N=171
Non-participation: N=210 125 Refused 31 Unable to contact 10 Moved away before interviewed 9 Died before interviewed 35 Unable to schedule*
Screened Negative (Neg) N=165
20% randomly selected N=33
80% end study participation N=132
Non-participation: Pos N=44 32 2 6
Neg N=7 7 -
Medical Refused Lost to follow-up Died *
Unable to schedule 4 N=75 Contact Person (CP) N=15 40 Participant refused CP 5 10 No CP available 1 12 CP refused 4 5 Unable to contact CP 5 1 Participant died 7
*
Unable to schedule
PHASE 2: Medical Assessment (N=127) CP Interview (N=96)
1 PHASE 2: Medical Assessment (N=26) CP Interview (N=18)
Case reviewed by consensus panel for diagnosis N=153
Fig. 1. Study flow diagram. *Unable to schedule interview before the end of data collection (September 30, 2012). TSI, Torres Strait Islander.
2.3. Outcomes Phase 2 medical assessment data were reviewed by a panel of three or more clinicians including at least one geriatrician and one clinical neuropsychologist. This panel made consensus determinations of cognitive impairment, dementia, and dementia type according to standard diagnostic criteria [12–16]. These included “all-cause” dementia [14], Alzheimer’s dementia (AD) [12,14], vascular dementia [12], dementia with Lewy bodies [13],
frontotemporal dementia [15], dementia due to the persisting effect of substance abuse [12], dementia due to other medical conditions [12], and mild cognitive impairment (MCI) [16]. 2.4. Statistical analysis Data were analyzed using IBM SPSS Statistics software (IBM, Armonk, NY, USA; version 21) and Microsoft Excel 2010 (Redmond, WA, USA). We
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determined crude and age-standardized prevalence rates for all-cause dementia, given the relatively young age of our study population relative to the general Australian population. Age standardization was calculated using a direct method [17] with reference to current Australian population estimates of dementia and age distribution for those aged 60 years and older [18]. The prevalence of dementia and MCI in the 20% random sample of high-scoring (screened negative) participants was inverse weighted to the full sample of high scorers. For 51 participants who were selected for phase 2, but did not complete a medical assessment (or consensus diagnosis), we based dementia diagnosis on a phase 1 MMSE score ,22 (to give 95% specificity in this population, as determined by preliminary analyses) [19] combined with any evidence of functional impairment [20]. Confidence intervals (CIs) were calculated using the asymptotic method with continuity correction [21] for crude rates and Chiang Poisson approximation method [22] for standardized rates. We also examined a range of demographic and clinical variables in our sample and used Pearson chi-square tests to compare men and women on these variables. Missing self-report data were imputed using CP responses where available.
3. Results 3.1. Participants The study census identified 546 eligible participants across the five study sites, which compared well with our reference figure of 609 Aboriginal or Torres Strait Islander people, based on available population statistics during the study (ABS, 2006). Of these, 336 (61.5%) participated in the study, aged 60 to 92 years (M 5 66.6 years, standard deviation [SD] 5 6.3 years). Reasons for exclusion or nonparticipation at each stage of the study are shown in the study flow diagram (Fig. 1). Participants did not differ significantly from eligible nonparticipants in terms of age, sex, or urban/regional distribution [7]. As detailed in Table 1, participants were predominantly Aboriginal (99.4%), female (59.5%), aged younger than 70 years (72.9%), and with some formal education (99.1%). All participants spoke English, typically as their first language (98.2%). Compared with women, men had significantly (P , .05) higher rates of head injury, heavy alcohol use, and prior prison/police custody and were more likely to have been in paid employment through their lifetime and to be currently married or in a de facto relationship. Women were more likely (P , .05) to have achieved at least 10 years of education, to be widowed or divorced, and to have had a fall in the past year. These results are shown in Tables 1 and 2. Based on phase 1 screening, 204 participants were selected to continue to study phase 2 (see Fig. 1). For
selected participants, there were no significant differences in age, sex, or MMSE scores between those who did (n 5 153) and did not (n 5 51) complete phase 2 medical/ cognitive assessments. One hundred fourteen CPs also participated. CPs were aged 23 to 82 years (M 5 52.3 years, SD 5 11.7 years), 71.9% (n 5 82) female, commonly the daughter (n 5 38; 33.3%) or spouse (n 5 27; 23.7%) of the participant, currently (n 5 48; 42.1%) or previously (n 5 38; 33.3%) lived with the participant, typically saw the participant daily (n 5 68; 59.6%), and reported knowing them well or very well (n 5 112; 98.2%). 3.2. Outcomes Of the 153 cases reviewed by the consensus panel, 41 cases of dementia and 38 cases of MCI were diagnosed. For dementia cases, 17 were classified as mild, 12 as moderate, and 12 as severe [23]. A further four cases of cognitive impairment were identified, related to chronic schizophrenia (n 5 2), developmental disorder (n 5 1), or delirium due to a general medical condition (n 5 1). There were no cases of dementia in the 20% randomly selected group of those with a negative phase 1 screening result (n 5 26), but four cases of MCI were identified in this group. Thus, prevalence of MCI was prorated for the remaining 139 participants with a negative screening result who did not complete a phase 2 medical assessment. Analysis of the 51 participants who were assigned to phase 2, but did not complete a medical assessment revealed four additional cases of dementia (two had refused a medical assessment and two had died), according to predefined criteria (described previously). Thus, the crude dementia prevalence rate was 13.4% (95% CI, 9.6–17.2) and the age-standardized rate was 21.0% (95% CI, 12.8–29.2). Fig. 2 shows dementia prevalence at different ages in the present study compared with a previous study in a remote Aboriginal population [3] and official estimates for the general Australian population (based on meta-analysis of data from Australia, Europe, and the United States) [18]. Prevalence of MCI was 17.7% (95% CI, 13.4–21.9). The total burden of cognitive impairment (including dementia, MCI, and other cognitive disorders) was 32.3% in this population. As depicted in Fig. 3, AD was the most common diagnosis of dementia, with 18 (43.9%) cases of probable AD. Other diagnoses of dementia included vascular dementia (n 5 7; 17.1%), dementia due to head trauma (n 5 3; 7.3%), and frontotemporal dementia (n 5 1; 2.4%). There were a further 12 cases (29.3%) with mixed dementia diagnoses. 4. Discussion The prevalence of dementia in the present urban/regional Aboriginal Australian population was comparable with rates found in a remote population at ages 60 years and older
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275
Table 1 Characteristics of sample on key demographic and social variables Total, n 5 336 Variable Indigenous status Aboriginal TSI Aboriginal and TSI Age group, y 60–69 70–79 801 Education ,10 y school 10 y education Basic literacy* Current residence Urban (Sydney) Regional (other NSW) Local area .20 yy Residential aged care Living alonez Marital status Married/de facto Widowed/divorced Never married Employment Currently employed Ever employed Main job, unskilledx Prison/police custody (past) Early life (birth to 15 years old) Residence Major city Regional/rural Remote Family stress One parent died Both parents died Removed from family Poor health{
N
%
328 2 6
98 1 2
245 77 14
Men, n 5 136 Missing data
Women, n 5 200
N
%
Missing data
N
%
Missing data
0 0 0
133 1 2
98 1 1
0 0 0
195 1 4
98 1 2
0 0 0
73 23 4
0 0 0
94 37 5
69 27 4
0 0 0
151 40 9
76 20 5
0 0 0
204 131 325
61 39 97
1 1 1
93 43 130
68 32 96
0 0 0
111 88 195
56 44 98
1 1 1
140 196 254 17 72
42 58 76 5 23
0 0 0 0 9
51 85 103 8 34
38 63 76 6 27
0 0 0 0 3
89 111 151 9 38
45 56 76 5 21
0 0 0 0 6
124 166 39
38 50 12
7 7 7
64 54 16
48 40 12
2 2 2
60 112 23
31 57 12
5 5 5
64 317 118 109
19 95 37 34
4 4 4 13
31 133 55 74
23 99 41 56
2 2 1 4
33 184 63 35
17 93 35 18
2 2 3 9
103 216 15
31 65 4
2 2 2
44 89 3
32 65 2
0 0 0
59 127 12
30 64 6
2 2 2
69 5 33 78
21 1 10 24
2 2 9 5
30 2 11 28
22 1 8 21
0 0 3 2
39 3 22 50
20 2 11 25
2 2 6 3
Abbreviations: TSI, Torres Strait Islander; NSW, New South Wales. *Adequate for Mini-Mental State Examination assessment. y Residing in the study catchment area for more than 20 years. z Excludes those living in residential aged care facilities. x Excludes those never employed, unskilled work includes laborers, cleaners, factory workers, etc. { Childhood health self-rated as poor/fair (vs. good/very good/excellent).
(23.8%; total n 5 168) [3]. The standardized rate of 21.0% is substantially (threefold) higher than the overall Australian population prevalence of 6.8% in this age range [18]. Consistent with previous studies in First World populations [24,25], our results showed that AD was most common (44% of cases), followed by vascular dementia (17% of cases). This pattern is highly similar to a population-based study of Australians aged 75 years and older [25], which found 43% of dementia cases were AD, 13% were vascular, and 30% were mixed. A similar pattern was also seen in remote Aboriginal communities [3]. In contrast to previously held opinion [26] and consistent with findings in remote Aboriginal communities [3],
dementia due to alcohol abuse was relatively uncommon in our urban population of older Aboriginal Australians. However, complex etiologies were frequently observed with close to a third of cases (n 5 12) meeting criteria for multiple types of dementia. Again, Alzheimer’s type presentations were common (i.e., possible AD)—a feature in nine (75%) of these mixed presentations. Dementia related to vascular pathology (n 5 7; 58%), head trauma (n 5 6; 50%), and alcohol abuse (n 5 4; 33%) were other key contributing factors in this mixed dementia group. Irrespective of diagnosis, our study showed high rates of stroke, head injury, and epilepsy, factors that were associated with dementia in the remote Aboriginal population [3].
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Table 2 Characteristics of sample on key medical and clinical variables Total, n 5 336
Men, n 5 136
Women, n 5 200
Variable
N
%
Missing data
N
%
Missing data
N
%
Missing data
Dementia Depression (lifetime) Anxiety (lifetime) Heavy alcohol (current)* Heavy alcohol (past)* Smoking (current) Hypertension Heart problems Stroke/TIA Diabetes Cancer Epilepsy Head injuryy Falls (past year) Hospital (past year) Disabilityz
45 114 95 65 168 86 205 140 78 144 40 25 95 78 132 166
13 35 29 20 52 26 63 43 24 44 12 8 29 24 41 51
0 11 11 11 14 11 12 10 10 9 11 13 10 11 14 11
24 39 31 39 93 36 80 61 31 54 15 6 56 23 60 59
18 29 23 29 70 27 60 46 23 40 11 5 42 17 45 45
0 3 3 3 4 3 3 3 2 2 4 5 3 4 3 5
21 75 64 26 75 50 125 79 47 90 25 19 39 55 72 107
11 39 33 14 39 26 65 41 24 47 13 10 20 28 38 55
0 8 8 8 10 8 9 7 8 7 7 8 7 7 11 6
Abbreviation: TIA, transient ischemic attack. *Measured by the Alcohol Use Disorder Identification Test – alcohol consumption questions (AUDIT-C) [37]. Heavy alcohol use defined as AUDIT-C 4. y Any head injury with loss of consciousness. z Some impairment of activities of daily living [20].
In contrast, lack of formal education was rare at just 1% of the present sample compared with 40% in remote Aboriginal people, where it was associated with dementia [3]. No significant difference in the dementia rate was found between men and women. The present study achieved recruitment of just over the targeted 60% of a population that was difficult to identify. This was due to the relatively small proportion of the total population within a given catchment area (i.e., 1.5%–11.1% across sites) and the absence of a formal registry of Aboriginal Australians. Although the sample size is lower than major dementia prevalence studies, such as the 10/66 Study [27], the present study is the largest population-based study of dementia to date for Aboriginal Australians in this age range (i.e., twice that of a previous 60
Prevalence rate (%)
50 40 Urban/regional
30
Remote
20
All Australia
10 0
60-69
70-79
80+
Age group (years)
Fig. 2. Dementia prevalence by age group: compares the current urban/ regional Aboriginal Australian population with a remote Aboriginal population (Smith et al. [3]) and the general Australian population (population projections based on data from Australia, Europe, and the United States, published by the Australian Institute of Health and Welfare, 2012 [18]).
study) [3]. The sample size, participation rate, and rate of progression/retention to phase 2 medical assessment and formal dementia diagnosis (75% of those screened/selected) were acceptable [24]. As opposed to the 10/66 single-phase approach (which avoids any such attrition), our study design allowed for a “gold standard” medical assessment with diagnosis by clinical consensus, adding to the validity of our results. We acknowledge it is possible that we missed some potential participants through our census process because of the limits of the snowballing technique. For example, Aboriginal people living within an area may not have been known to the local community or Aboriginal controlled services, particularly in city sites. Our additional recruitment technique through mainstream health services was only partly successful because of the inaccurate or incomplete records of the Indigenous status held by such services. Moreover, given that part of our recruitment approach was directed through primary health services, it is possible that our sample could have been biased to those who were sicker or who were more likely to be experiencing cognitive impairment; however, subsequent snowballing was carried out by our independent Aboriginal researchers. We also identified and recruited relatively few people in residential aged care facilities, which contributed significant dementia numbers in a previous study [3]. Limited evidence regarding the validity of cognitive measures and normative reference criteria in our study population made it challenging to diagnose MCI and subtle cognitive impairment. The present study further aims to validate and compare selected cognitive screening tests in this population, whereas a longitudinal follow-up will explore the progression rate of MCI to dementia. Clinical
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Fig. 3. Frequency of dementia types diagnosed, by clinical consensus according to formal dementia criteria [12–15], of 41 cases in the current urban/regional Aboriginal Australian population.
examination with subsequent consensus diagnosis remains uncertain in a population with multiple potential risk factors and without the availability of normative reference criteria, neuroimaging, or an autopsy sample. Consideration of genetic risk factors, particularly apolipoprotein E polymorphisms [28], is also important. The use of genetic and biomarker research technologies in Aboriginal populations raises several historical and cultural challenges. Nonetheless, these should be explored as options for future work in close consultation and collaboration with Aboriginal communities to ensure an equitable high standard of research. However, as found in the United States [29], modifiable social and healthrelated risk factors are likely to have a bigger impact than genetic risk in accounting for differences in dementia between Aboriginal and nonindigenous Australians. The question now remains as to why there are much higher rates of dementia in older urban Aboriginal Australians compared with many other populations worldwide. The potential risk factors for cognitive decline and dementia in this population are multiple and varied. A range of factors across the life course could be contributing, directly and indirectly, to high dementia prevalence. It is likely that both early life environmental factors (e.g., low education levels, low socioeconomic status, trauma, and other adverse events) [29–31] and mid–late life biomedical factors (e.g., vascular and metabolic risk, prior head injury) [29] are driving these higher dementia rates that are common to remote and urban Aboriginal populations. In socioeconomically disadvantaged populations (including ethnic minorities and Fourth World Indigenous people), low education and illiteracy have been frequently identified as important factors linked to increased dementia risk [3,29,31–33] Although almost our entire urban sample had received some schooling and demonstrated basic literacy, the level of education in the urban Aboriginal population is considerably lower than in other older Australians; 61% of Australians aged 65 years and over have achieved 10 years of education or more [34] compared
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with 19% in the present sample. In addition, we are examining the influence of education quality (e.g., attendance, learning disabilities, parental attitudes, and discrimination within the education system) and informal educational opportunities (i.e., enriched learning environment beyond school) on cognitive decline and dementia. Disparately high prevalence of cardiovascular diseases and diabetes mellitus in many disadvantaged populations has also been associated with greater rates of dementia [2,3,29]. An excess burden of vascular and metabolic diseases (risk factors) is apparent in Aboriginal Australians [5], and these were common in our sample. There could also be other, less obvious but nonetheless pervasive, risk factors influencing cognitive decline and higher dementia rates in this population, including early life stress [35] and head trauma [3,36]. We are planning further analysis of the present data set, coupled with longitudinal follow-up, which will help to understand these risk factors. Acknowledgments The Koori Growing Old Well Study (KGOWS) is a collaboration between Neuroscience Research Australia (NeuRA), University of NSW, and Aboriginal and academic research partners. Our collaborators include our Aboriginal partner communities, Aboriginal health managers in NSW Area Health Services (Gail Daylight, Vicki Wade, and Tim Agius), Muru Marri Indigenous Health Unit UNSW, Dementia Collaborative Research Centres, Prince of Wales Hospital, KICA Research Group at University of Western Australia, ARC-NHMRC Ageing Well Network, and the National Aboriginal and Torres Strait Islander Dementia Advisory Group at Alzheimer’s Australia. This work relied on the assistance and support of many individuals and organizations. The authors are particularly grateful to our participants; our local Elder guidance groups, KGOWS Aboriginal Reference Group; and our Aboriginal community partners who continue to offer their support for our research: Durri Aboriginal Corporation Medical Service and Booroongen Djugun in Kempsey, Darrimba Maarra Aboriginal Health Clinic in Nambucca, Galambila Aboriginal Health Service in Coffs Harbour, La Perouse Local Aboriginal Land Council, La Perouse Aboriginal Community Health Centre, and Tharawal Aboriginal Corporation in Campbelltown. We wish to recognize the hard work of our research team including Aboriginal research assistants (Bridget Jarrett, Gail Ling, Garth Fatnowna, Heidi Sainsbury, Margaret Anderson, Mervyn Davison, Michele Stewart, Sue Hoskins, and Sue Parsons), project officers and interviewers (Cecilia Minogue, Christine Metusela, Emily Hindman, Emma Schofield, Jennifer Japhet, Jennifer Sperring, Kristen Holdsworth, Lea Williams, Natalie Johnson, Rachelle Arkles, Renee Ward, and Wendy Hampshire), medical doctors (Anthony French, Brenda McPhee, Matthew Kinchington, Tabitha Hartwell, and
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William Brooks), and administrative support (Hamish Robertson, Jan Koh, and Sandra Forster). We also acknowledge Professor Lisa Jackson Pulver for her contribution to the study design and Associate Professor Emeritus David Grayson for his contribution to the design and initial implementation of the study and ongoing advice regarding data management and analyses. Funding sources: This study was supported by an Australian National Health and Medical Research Council Project Grant (510347). Initial piloting was funded by the Dementia Collaborative Research Centres (IPW02) and Alzheimer’s Australia Research. The project also received donations via the Ageing Research Centre at Prince of Wales Hospital, Sydney. K.R. is funded by the RW & JG Postdoctoral Fellowship in Aboriginal Health and Ageing.
RESEARCH IN CONTEXT
1. Systematic review: We searched OVID and MEDLINE databases for studies of dementia prevalence in the major Fourth World Indigenous people (i.e., from Canada, United States, New Zealand, and Australia), identifying only two previous cross-sectional studies [2,3]. 2. Interpretation: There is a major lack of epidemiologic data on dementia in these Fourth World Indigenous populations. The present results are comparable with findings in a remote Aboriginal population [3] and provide further evidence that Aboriginal Australians experience some of the highest rates of dementia reported worldwide. 3. Future directions: Alzheimer’s disease dementia was common, but high rates of other potential causes or risks factors for dementia (e.g., vascular, head trauma) were also observed. Longitudinal research, in addition to neuroimaging and genetic data, is needed to understand the social and biomedical risk factors contributing to the high dementia rates in urban, regional, and remote Aboriginal Australians.
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