A system dynamics modelling approach to studying the increasing prevalence of people with intellectual developmental disorders in New South Wales
Lynette Lee A F , Mark Heffernan B , Geoffrey McDonnell C , Stephanie D. Short D and Vasi Naganathan EA School of Medicine Sydney, University of Notre Dame Australia, 160 Oxford Street, Darlinghurst, NSW 2010, Australia.
B Dynamic Operations, 5/10 Surfview Road, Mona Vale, NSW 2103, Australia. Email: mark@dynamicoperations.com.au
C Australian Institute of Health Innovation, AGSM Building, UNSW Australia, Kensington, NSW 2052, Australia. Email: gmcdonne@bigpond.net.au
D Discipline of Behavioural and Social Sciences in Health, Faculty of Health Sciences, University of Sydney, Lidcombe, NSW 2141, Australia. Email: stephanie.short@sydney.edu.au
E Centre for Education and Research on Ageing, University of Sydney, Concord Hospital, Concord, NSW 2139, Australia. Email: vasi.naganathan@sydney.edu.au
F Corresponding author. Email: lyn-lee@bigpond.net.au
Australian Health Review 40(3) 235-243 https://doi.org/10.1071/AH14150
Submitted: 2 September 2014 Accepted: 17 July 2015 Published: 12 October 2015
Abstract
Objective The aims of this study were to estimate the prevalence count of people with intellectual developmental disorders (IDD) in New South Wales (NSW) in 2003, by age groups, and to forecast their prevalence until 2043.
Methods Administrative data obtained from NSW government departments of education, pensions, health and disability were used to profile the number of people whose characteristics met the criteria for ‘intellectual developmental disorders’ who had received services in 2003. These figures were compared with published tables of NSW data from the national self-report Survey of Disability, Ageing and Carers (SDAC) of 2003 to estimate the likely prevalence of people with intellectual developmental disorders, by age groups in that year. The results were then used as baseline figures in a computational system dynamics model of the aging chain of people with these disorders, built to project prevalence to 2043.
Results The number of people who met the criteria for having intellectual developmental disorder in NSW in 2003 was estimated to be 57 000 (a ratio of 85 per 10 000), with 32 000 aged 0–15 years, 15 000 aged 16–39 years, 9000 aged 40–64 years and 1000 aged 65+ years. Using these figures as baseline, the computer simulation predicted a total increase to 77 225 people in 2013 and 135 905 people by 2043. By 2043, the number of children with intellectual developmental disorders will have doubled, from 32 000 to 59 480, and the number of adults will have tripled, from 25 000 to 76 420.
Conclusions This modelling technique forecast an increase in the prevalence count of people with intellectual developmental disorders in NSW over the period 2003–43 from 57 000 (85 per 10 000) to 135 905 (135 per 10 000). These predictions may have important implications for the planning of specialist health services for this group of people.
What is known about the topic? The prevalence ratio of people with intellectual developmental disorders is quoted at lying between 1% and 2% of the Australian population, depending on the definition adopted. It is known that life expectancy for this group of people is increasing. Many people with intellectual developmental disorders have multiple service demands and there is a need to understand the prevalence count in various age groups in order to plan effectively for their health service needs.
What does this paper add? This paper confirms a NSW prevalence ratio of people with intellectual developmental disorders of approximately 0.85% for the purposes of specialist health service planning at the beginning of the 21st century, and this is predicted to increase to 1.35% over a 40-year period. The paper demonstrates that there will be significant growth in the number of adults surviving to old age between 2003 and 2043.
What are the implications for practitioners? It is known that as people with intellectual developmental disorders age, their health promoting care needs increase, as do their dependencies on special supports. Planning for the allocation of resources associated with the welfare and healthcare of people with intellectual developmental disorders may need to be focused on this anticipated increase in the number of older people with the condition.
References
[1] World Health Organization (WHO). International classification of functioning, disability and health. Geneva: WHO; 2001.[2] World Health Organization (WHO). Intellectual disability. 2015. Available at: http://www.euro.who.int/en/health-topics/noncommunicable-diseases/mental-health/news/news/2010/15/childrens-right-to-family-life/definition-intellectual-disability [verified 11 January 2015].
[3] Salvador-Carulla L, Reed GM, Vaez-Azizi LM, et al Intellectual developmental disorders: towards a new name, definition and framework for ‘mental retardation/intellectual disability’ in ICD-11. World Psych 2011; 10 175–80.
[4] Haveman M, Heller T, Lee L, Maaskant M, Shooshtari S, Strydom A. Major health risks in aging persons with intellectual disabilities: an overview of recent studies. J Policy Pract Intell Disabil 2010; 7 59–69.
| Major health risks in aging persons with intellectual disabilities: an overview of recent studies.Crossref | GoogleScholarGoogle Scholar |
[5] Australian Institute of Health and Welfare. Available at: http://www.aihw.gov.au/disability-data-cubes/ [verified 10 July 2015].
[6] Bittles AH, Petterson BA, Sullivan SG, Hussain R, Glasson EJ, Montgomery PD. The influence of intellectual disability on life expectancy. J Gerontol A Biol Sci Med Sci 2002; 57 M470–2.
| The influence of intellectual disability on life expectancy.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD38zltFClug%3D%3D&md5=c3d824a71d4fd3b9fb87df26e57a8178CAS | 12084811PubMed |
[7] NSW Health. A service framework to improve the health care of people with Intellectual Disability. Sydney: NSW Ministry of Health; 2012.
[8] American Psychiatric Association (APA). Diagnostic and statistical manual of mental disorders (DSM-5R). Michigan: APA; 2013.
[9] Australian Government. Guidelines to the tables for the assessment of work-related impairment for DSP, Table 9 intellectual function. 2012. Available at: http://guides.dss.gov.au/guide-social-security-law/3/6/3/90 [verified 10 July 2015].
[10] Ageing Disability and Home Care. Client information system annual report database 2009/10: Family and Community Services. Sydney: Ageing Disability and Home Care; 2010.
[11] MacMillan DL, Gresham F, Siperstein G. Conceptual and psychometric concerns about the 1992 AAMR definition of mental retardation. Am J Ment Retard 1993; 98 325–35.
| 1:STN:280:DyaK2c7itFymsQ%3D%3D&md5=7a955c4f0be5e4d42da5bf4d4e9410b2CAS | 8292309PubMed |
[12] MacMillan DL, Gresham F, Siperstein G. Heightened concerns over the 1992 AAMR definition: advocacy versus precision. Am J Ment Retard 1995; 100 87–95.
| 1:STN:280:DyaK28%2FlsFykug%3D%3D&md5=bbf9e5850767204b4fb8cd05fb042faeCAS | 7546640PubMed |
[13] Patton J, Beirne-Smith M, Payne J. Mental retardation. New York: Macmillan; 1990.
[14] Evans I. Testing and diagnosis: a review and evaluation. In: Meyer L, Peck C, Brown L, editors. Critical issues in the lives of people with severe disabilities. Baltimore: Paul H Brookes Publishing; 1991; pp. 25–44.
[15] Anderson LL, Humphries K, McDermott S, Marks B, Sisirak L, Larson S. The state of the science of health and wellness for adults with intellectual and developmental disabilities. Intellect Dev Disabil 2013; 51 385–98.
| The state of the science of health and wellness for adults with intellectual and developmental disabilities.Crossref | GoogleScholarGoogle Scholar | 24303825PubMed |
[16] Emerson E. Health status and health risks of the “hidden majority” of adults with intellectual disability. Intellect Dev Disabil 2011; 49 155–65.
| Health status and health risks of the “hidden majority” of adults with intellectual disability.Crossref | GoogleScholarGoogle Scholar | 21639742PubMed |
[17] Krahn GL, Hammond L, Turner A. A cascade of disparities: health and health care access for people with intellectual disabilities. Ment Retard Dev Disabil Res Rev 2006; 12 70–82.
| A cascade of disparities: health and health care access for people with intellectual disabilities.Crossref | GoogleScholarGoogle Scholar | 16435327PubMed |
[18] Maulik PK, Mascarenhas MN, Mathers CD, Dua T, Saxena S. Prevalence of intellectual disability: a meta-analysis of population-based studies. Res Dev Disabil 2011; 32 419–36.
| Prevalence of intellectual disability: a meta-analysis of population-based studies.Crossref | GoogleScholarGoogle Scholar | 21236634PubMed |
[19] Wullink M, van Schrojenstein Lantman-de Valk H, Dinant GJ, Metsemakers JFM. Prevalence of people with intellectual disability in The Netherlands. J Intellect Disabil Res 2007; 51 511–9.
| Prevalence of people with intellectual disability in The Netherlands.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD2szisFCksQ%3D%3D&md5=26fb6750f8c29c3633dff8a686552c27CAS | 17537164PubMed |
[20] van Schrojenstein Lantman-de Valk HM, Wullink M, van den Akker EWA, van Heurn-Nijsten JFM, Metsemakers JFM, Dinant GJ. The prevalence of intellectual disability in Limburg, The Netherlands. J Intellect Disabil Res 2006; 50 61–8.
| The prevalence of intellectual disability in Limburg, The Netherlands.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD2MnjsF2isQ%3D%3D&md5=29655e298110d479f2f5a7ef3534c8cbCAS | 16316431PubMed |
[21] Ouellette-Kuntz H, Shooshtari S, Temple B, Brownell M, Burchill C, Holden JJA, Hennen B. Estimating administrative prevalence of intellectual disabilities in Manitoba. J Dev Disabil 2009; 15 69–80.
[22] McDonald G, MacKay DN. The prevalence of learning disability in a health and social services board in Northern Ireland. J Intellect Disabil Res 1996; 40 550–6.
| The prevalence of learning disability in a health and social services board in Northern Ireland.Crossref | GoogleScholarGoogle Scholar | 9081517PubMed |
[23] Mulvany F, Barron S. Annual report 2002. Dublin: National Intellectual Disability Database Committee, Health Research Board of Ireland; 2003.
[24] Patja K, Iivanainen M, Vesala H, Oksanen H, Ruoppila I. Life expectancy of people with intellectual disability: a 35-year follow-up study. J Intellect Disabil Res 2000; 44 591–9.
| Life expectancy of people with intellectual disability: a 35-year follow-up study.Crossref | GoogleScholarGoogle Scholar | 11079356PubMed |
[25] Esbensen AJ, Seltzer MM, Greenberg JS. Factors predicting mortality in mid-life adults with and without Down syndrome living with family. J Intellect Disabil Res 2007; 51 1039–50.
| Factors predicting mortality in mid-life adults with and without Down syndrome living with family.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD2snms1Grtg%3D%3D&md5=3b5a0520c1c346f40a134a0e33d51e78CAS | 17991011PubMed |
[26] Lemay RA. Deinstitutionalization of people with developmental disabilities: a review of the literature. Can J Commun Ment Health 2009; 28 181–94.
| Deinstitutionalization of people with developmental disabilities: a review of the literature.Crossref | GoogleScholarGoogle Scholar |
[27] Forrester JW. System dynamics: a personal view of the first fifty years. Syst Dyn Rev 2007; 23 345–58.
| System dynamics: a personal view of the first fifty years.Crossref | GoogleScholarGoogle Scholar |
[28] Forrester JW. Industrial dynamics. Portland: Productivity Press; 1961.
[29] Homer JB, Hirsch G, Milstein B. Chronic illness in a complex health economy: the perils and promises of downstream and upstream reforms. Syst Dyn Rev 2007; 23 313–43.
| Chronic illness in a complex health economy: the perils and promises of downstream and upstream reforms.Crossref | GoogleScholarGoogle Scholar |
[30] Milstein B, Homer JB, Hirsch G. Analyzing national health reform strategies with a dynamic simulation model. Am J Public Health 2010; 100 811–19.
| Analyzing national health reform strategies with a dynamic simulation model.Crossref | GoogleScholarGoogle Scholar | 20299653PubMed |
[31] Homer JB. Models that matter: selected writings on system dynamics 1985–2010. New York: Grapeseed Press; 2012.
[32] Wolstenholme E, McKelvie ND, Smith G, Monk D. Using system dynamics in modelling health and social care commissioning in the UK. Teddington; 2004. Available at: http://www.systemdynamics.org/conferences/2004/SDS_2004/PAPERS/116SMITH.pdf [verified 15 July 2015].
[33] McDonnell G, Heffernan M. Health care system dynamics insights. Sydney: Systemswiki; 2012. Available at: http://www.systemswiki.org/index.php?title=Health_Care_System_Dynamics_Insights [verified 10 July 2015].
[34] Chalmers J, Ritter A, Heffernan M, McDonnell G. Modelling pharmacotherapy maintenance in Australia: exploring affordability, availability, accessibility and quality using system dynamics. Research Paper No. 19. Civic Square, ACT: Australian National Council on Drugs; 2009.
[35] Atkinson JA, Wells R, Page A, Dominello A, Haines M, Wilson A. Applications of system dynamics modelling to support health policy. Public Health Research Practice 2015; 25 e2531531
| Applications of system dynamics modelling to support health policy.Crossref | GoogleScholarGoogle Scholar |
[36] Forrester JW. The ‘model’ versus the modeling ‘process’. Syst Dyn Rev 1985; 1 133–4.
| The ‘model’ versus the modeling ‘process’.Crossref | GoogleScholarGoogle Scholar |
[37] Sparrow SS, Cicchetti DV, Balla DA. Vineland adaptive behavior scales, 2nd edn. San Antonio: PsychCorp; 2005.
[38] Weschler D. The measurement and appraisal of adult intelligence, 4th edn. Baltimore, MD: Williams and Wilkins; 1958.
[39] NSW Education and Communities. Educational services supporting students with disability. 2011. Available at: http://www.schools.nsw.edu/media/downloads/schoolsweb/studentsupport/programs/disabilitypgrms/eduservices-studisability.pdf [verified 15 July 2015].
[40] Ageing Disability and Home Care. National minimum data set data for annual report. Sydney: ADHC; 2005.
[41] NSW Health. Hospital separations for mental retardation NSW Hospitals 2003–2006. Sydney: NSW Health; 2006.
[42] Centrelink. Disability Support Pension data Australia 2001–2009. Canberra: Centrelink; 2009.
[43] Bigby C, Webber R, Bowers B, Mckenzie-Green B. A survey of people with intellectual disabilities living in residential aged care facilities in Victoria. J Intellect Disabil Res 2008; 52 404–14.
| A survey of people with intellectual disabilities living in residential aged care facilities in Victoria.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD1c3lsFSmsA%3D%3D&md5=3ac677731ba9de4eeed371a1e0f3dd34CAS | 18205755PubMed |
[44] Wen X. The definition and prevalence of intellectual disability in Australia. Canberra: Australian Institute of Health and Welfare; 1997.
[45] Australian Institute of Health and Welfare (AIHW). Disability in Australia: intellectual disability. Catalogue no. AUS 110 (Bulletin 67). Canberra: AIHW; 2008
[46] Australian Bureau of Statistics. Disability ageing and carers, Australia: summary of findings, 2003. 2004. Available at: http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/4430.02003?OpenDocument [verified 7 September 2015].
[47] Australian Institute of Health and Welfare (AIHW). Disability and disability services in Australia. Canberra: AIHW; 2005.
[48] Australian Bureau of Statistics. Survey of disability, ageing and carers 2012. 2014. Available at: http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/4430.02012?OpenDocument [verified 15 July 2015].
[49] Australian Bureau of Statistics (ABS). How many people have intellectual disability? Canberra: ABS; 2014.
[50] Australian Institute of Health and Welfare (AIHW). Australia’s Welfare 2005. Canberra: AIHW; 2005.
[51] Australian Bureau of Statistics Disability. Ageing and carers: summary of findings. Canberra: ABS; 2004.
[52] Australian Bureau of Statistics (ABS). 3222.0: population projections, Australia, 2012 to 2101. 2012. Available at: http://www.abs.gov.au/ausstats/abs@.nsf/Latestproducts/3222.0Main%20Features72012%20(base)%20to%202101?opendocument&tabname=Summary&prodno=3222.0&issue=2012%20(base)%20to%202101&num=&view= [verified 10 January 2015].
[53] Larson S, Lakin C, Anderson L, Lee NK, Lee JH, Anderson D. Prevalence of mental retardation and developmental disabilities: estimates from the 1994/1995 national health interview survey disability supplements. Am J Ment Retard 2001; 106 231–52.
| Prevalence of mental retardation and developmental disabilities: estimates from the 1994/1995 national health interview survey disability supplements.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD3MzktlygtA%3D%3D&md5=1653751c4fb0863521d1249bcfc000dbCAS | 11408960PubMed |
[54] McConkey R, Mulvany F, Barron S. Adult persons with intellectual disabilities on the island of Ireland. J Intellect Disabil Res 2006; 50 227–36.
| Adult persons with intellectual disabilities on the island of Ireland.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD28%2FktleqsA%3D%3D&md5=3eec2b483816c48dccb08b8031d3247dCAS | 16430733PubMed |
[55] Westerinen H, Kaski M, Virta L, Almqvist F, Iivanainen M. Prevalence of intellectual disability: a comprehensive study based on national registers. J Intellect Disabil Res 2007; 51 715–25.
| Prevalence of intellectual disability: a comprehensive study based on national registers.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD2srjtFOgsg%3D%3D&md5=26104029412e40f7307c9a6aac54f60eCAS | 17845240PubMed |
[56] Cooper S, Smiley E, Morrison J, et al Mental ill-health in adults with intellectual disabilities: prevalence and associated factors. Br J Psych 2007; 190 27–35.
| Mental ill-health in adults with intellectual disabilities: prevalence and associated factors.Crossref | GoogleScholarGoogle Scholar |
[57] Søndenaa E, Rasmussen K, Nottestad JA, Lauvrud C. Prevalence of intellectual disabilities in Norway: domestic variance. J Intellect Disabil Res 2010; 54 161–7.
| Prevalence of intellectual disabilities in Norway: domestic variance.Crossref | GoogleScholarGoogle Scholar | 20015168PubMed |
[58] Einfeld SL, Tonge BJ. Population prevalence of psychopathology in children and adolescents with intellectual disability: 11 epidemiological findings. J Intellect Disabil Res 1996; 40 99–109.
| Population prevalence of psychopathology in children and adolescents with intellectual disability: 11 epidemiological findings.Crossref | GoogleScholarGoogle Scholar | 8731467PubMed |
[59] Beange H, Taplin JE. Prevalence of intellectual disability in northern Sydney adults. J Intellect Disabil Res 1996; 40 191–7.
| Prevalence of intellectual disability in northern Sydney adults.Crossref | GoogleScholarGoogle Scholar | 8809660PubMed |
[60] Shreckengost RC. Dynamic simulation models: how valid are they? In: Self-Report Methods of Estimating Drug Use: Meeting Current Challenges to Validity. Eds Rouse BA, Kozel NJ, Richards MSLG. NIDA Research Monograph National Institute on Drug Abuse. Rockville: National Institute on Drug Abuse, Department of Health and Human Services; 1985; 57: 63–70.
[61] Australian Bureau of Statistics (ABS). Disability ageing and carers 2009 state data for NSW. Canberra: ABS; 2012.
[62] Australian Bureau of Statistics (ABS) Intellectual Disability Australia. 2014. Available at: http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/4433.0.55.003main+features102012 [verified 15 July 2015].
