More people with an intellectual disability are now living to older age and there is a paucity of information about this group of people. Mental illness is 2-3 times more prevalent in people with an intellectual disability than in the general community; however, this often goes undiagnosed and undetected. Additional issues complicate assessment if the person is also ageing. Little is known about the prevalence and nature of mental illness in this group of older people. Instruments used to assist in the diagnosis of mental illness in the general community are not suitable for use with individuals who have an intellectual disability. The Developmental Behavioural Checklist for Adults (DBC-A) (Mohr, Tonge & Einfeld, 2005) is a well established screen for psychopathology; however, it has no standardised norms and has not been specifically validated for older adults. Lack of knowledge and inadequate assessment processes can result in inappropriate service delivery and therefore reduced quality of life for older people with an intellectual disability and their carers. The general aim of the research was to contribute knowledge about older people with an intellectual disability and more specifically to investigate their mental health. In addition, the validity of the DBC-A for use with older adults was examined. An epidemiological study of adults aged 55 years and older, who lived in representative areas in South Australia, and who were registered with intellectual disability service agencies, were surveyed. Familiar informants completed a questionnaire booklet (see Appendix A). The Adaptive Behaviour Dementia Questionnaire (ABDQ) (Prasher, Farooq & Holder, 2004) and, for a subset of the participants, the Dementia Screening Questionnaire for Individuals with Intellectual Disability (DSQIID) (Deb, Hare, Bhaumik et al., 2007a) were also completed (see Appendices F and G). There was a participation rate of 91.7% and participants’ ages ranged from 55-86 years, the majority being males (56.6%), except in the oldest cohort. Those aged 55-64 years appears to differ from those who are older and younger. They have more severe intellectual impairments, more chronic health conditions, they are less likely to be engaged in activities, and have fewer relationships. Those older than 65 years are more similar to older people without an intellectual disability except that more live in nursing homes or larger congregate care settings. Standardised normative data was established for the DBC-A for older people. The DBC-A profile showed age-associated decline in psychopathology; however, the intensity of behaviours was higher in older people with more severe cognitive impairment. Significant psychopathology was found in 16% of older adults. There were no gender differences but those with a moderate level of intellectual disability had the highest rates. Being younger, having fewer hours in activity, living in large congregate care and significant life events were all risk factors. Rates of dementia of between 5-7% were found using the ABDQ, DSQIID and respondent report. A dementia screen using items from the DBC-A (DBC-A Dem) identified almost double that number. There was no association between age and dementia status in this study, which differs from other research, as does the lack of relationship between having Down syndrome and dementia status. The results of this study confirm a picture of differential mortality and the presence of a healthy survivor cohort who have fewer chronic health problems and are more likely to have a mild level of intellectual disability. Although there is an age-related decline in the prevalence of mental illness, rates are still one and a half times more than older people who do not have an intellectual disability. With minor amendments, the DBC-A is a valid screening instrument for use with older people with an intellectual disability. It can record changes in a wide range of emotional and behaviour disturbances including those that may affect older people, including dementia. When used with other DBCs for children and adolescents (Einfeld & Tonge, 1995) it provides a simple and familiar way to record psychopathology throughout the lifespan. This offers clinicians, researchers and service providers a means to monitor and maintain the mental health and well-being of older people with an intellectual disability.
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