The 2012-13 National Aboriginal and Torres Strait Islander Health Survey (NATSIHS) and National Aboriginal and Torres Strait Islander Nutrition and Physical Activity Survey (NATSINPAS) collected data on a broad range of health conditions a person may have, with the primary focus on current and long-term conditions. Some conditions, including National Health Priority Area (NHPA) conditions, are of great importance in policy planning and are specifically asked in individual modules to ensure high quality detailed results for these conditions. For collection methodology and interpretation specific to each condition, the appropriate topic page should be reviewed.
The following NHPA conditions as well as kidney disease were collected in both the NATSIHS and the NATSINPAS and therefore information is available for the larger Core sample:
- heart and circulatory conditions
- diabetes mellitus.
In addition to these, the NATSIHS collected information on the following five NHPA conditions:
- mental health (limited).
NATSIHS also collects information on sight and hearing and other long-term conditions. Note that selected mental health conditions ('feeling depressed' and 'depression') are collected within the Other Long-term Conditions module. Additional information on mental health and wellbeing, including psychological distress, are collected within the NATSIHS social and emotional wellbeing section of the questionnaire (referred to in the Mental Health and Well-being
page of this Users' Guide).
In the NHPA conditions and kidney disease modules, respondents are specifically asked whether they have been diagnosed with the condition. Respondents are also asked whether the condition is current and long-term except where an assumption is made (e.g. cancers are considered to be long-term if they are identified as current). This is discussed in more detail in the individual sections on these conditions later in this chapter. Each reported condition was then classified into the following condition status output categories:
- ever told has condition, still current and long-term
- ever told has condition, still current but not long-term
- ever told has condition, not current.
An additional category 4: 'not known if ever told or not ever told, but condition current and long-term' is also used in the NATSIHS where respondents are not asked about diagnosis. It is specifically used for sight and hearing conditions as well as any other long-term health conditions reported which had lasted, or were expected to last, for six months or more. Category 4 also applies to conditions in NATSIHS where NHPA conditions or kidney disease were reported in the long-term conditions module and did not trigger a diagnosis question.
Respondents without a condition are classified into category 5: 'never told, not current or long-term'.
Condition prevalence is usually reported based on categories 1 and 4 (where applicable in NATSIHS), i.e. that the condition is current and long-term. Current long-term conditions are defined as medical conditions (illnesses, injuries or disabilities) which were current at the time of the survey and which had lasted at least six months, or which the respondent expected to last for six months or more, including:
- long-term conditions from which only infrequent attacks may occur
- long-term conditions which may be under control, for example, through the continuing use of medication
- conditions which, although present, may not be generally considered ‘illness’ because they are not necessarily debilitating, e.g. reduced sight
- long-term or permanent impairments or disabilities.
In addition to the above conditions, NATSIHS and NATSINPAS collected information on self-assessed health, and NATSIHS also collected information on disabilities and recent injuries.
Classification of conditions
Conditions reported by respondents were coded to a single list of approximately 1000 specific condition and condition group categories (referred to as the "1000 input code list" in this publication). This list covers the more common types of long-term conditions experienced in the Australian community. The list was initially developed by the Family Medicine Research Centre at the University of Sydney, in consultation with the ABS, for the 2001 National Health Survey (NHS) (and used for the 2001 National Health Survey (Indigenous)). The detailed output classification used for ABS Health surveys (including NATSIHS) since 2001 was developed by the ABS based on mapping between the 1000 input code list and the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10)
provided by the Family Medicine Research Centre. The classification takes into account:
- the types of long-term conditions more commonly reported in a population based survey and for which reliable estimates could be produced
- the types of conditions or groups of conditions known to be of particular interest to data users
- the variability of the descriptions of conditions provided by respondents.
While information from the ICD-10
was used in the development of this list, results are generally not available classified to the most detailed condition level based on ICD-10. As the data are from a sample survey, there are not enough observations to support reliable estimates at that level of detail.
A computer-based coding system was developed by the ABS based on this list, and interviewers were able to select from it using a trigram coder which was built into the CAI instruments. Predefined response categories in the questionnaires were allocated unique codes within the 1000 input code list.
For the majority of conditions, interviewers were able to select the appropriate condition from either category responses for questions or from a trigram coder attached to ‘other’ response categories. Where the interviewer could not find the condition in the coder or the condition name was not known at the time of the interview, efforts were made to ensure that the description of each condition which was recorded at interview was as precise and informative as possible to enable detailed, accurate and consistent coding of conditions. The standard classification of medical conditions available from the NATSIHS and a reduced classification produced specifically for NATSINPAS and the Core output, is contained in Appendix 2: Classification of health conditions
Points to consider
- It is expected that conditions which were specifically mentioned in questions or (to a lesser extent) shown on prompt cards would have been better reported than conditions for which responses relied entirely on respondent judgement and willingness to report them. Data are not available from this survey to enable the magnitude of this effect to be quantified, but it is likely to differ across condition types and for different groups in the population.
- As a result of a prompt card being incorrectly excluded from the NATSIHS in the Other long-term conditions section of the questionnaire, the only mental health conditions available for output as part of the ICD-10 classification are those of 'feeling depressed' and 'depression'. However, due to the method used to collect conditions it was still possible for respondents to report other mental health conditions via responding to questions which had the trigram coder attached. These responses are excluded from the ICD-10 data item (on the Conditions level) but are included in the 'Number of conditions reported (incl. not current or long-term)' and 'Number of long-term conditions reported' data items (located on the Person level). Therefore, counts of conditions based on the conditions reported in the ICD-10 data item will not match those of these specifically created data items.
- Although in NATSIHS long-term/permanent disabilities were within the scope of general conditions data, data output from the ICD-10 should not be interpreted as indicating the disabled population. In some cases, long-term/permanent impairment/disability could be evident from the condition categories, e.g. blindness (complete or partial), while for others some degree of impairment/disability could be inferred from the nature of the condition, e.g. arthritis, back problems. However, these data should, at best, be considered as proxy indicators of disability only. See the Disability page of this Users' Guide for more information.
- As the NATSINPAS only collected data for specific condition modules and required diagnosis, there was no opportunity to pick up conditions that may be recalled later in the survey through promptings, such as prompts used in the NATSIHS long-term conditions module. Some differences in prevalence rates may therefore be apparent, particularly as reported NATSIHS prevalence rates included conditions that are not identified as diagnosed but are long-term and current whereas this population is not available in the production of NATSINPAS or core prevalence rates.
- As many population characteristics are age-related, (for example, long-term health conditions and employment patterns), adjustments are made to account for the confounding effects of the different age structures on the prevalence of these characteristics. Age standardisation is a technique used to enhance the comparability of rates between populations with different age structures. The Aboriginal and Torres Strait Islander population has a larger proportion of young people and a smaller proportion of older people than the non-Indigenous population. For this reason, where appropriate, estimates for Aboriginal and Torres Strait Islander people and non-Indigenous people in AATSIHS publications have both been age standardised to reflect the age structure of the same population — the total estimated resident population of Australia as at 30 June 2001. The age standardised rates are the rates that would have prevailed if both populations had this same age structure.