The 2014-15 NHS collects data on a broad range of health conditions a person may have, with the primary focus on current and long-term conditions. Some conditions have been selected to be of greater 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 section should be reviewed.
These conditions are:
- Heart and circulatory conditions
- Diabetes mellitus
- Kidney disease
- Mental, behavioural and cognitive conditions.
Throughout this Users' Guide these conditions are referred to as priority, targeted conditions.
The 2014-15 NHS also collects information on sight and hearing and other long-term conditions.
In the specific conditions modules, respondents are specifically asked whether they have been diagnosed. 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. Each reported condition was then classified into the following condition status output categories:
1. Ever told has condition, still current and long-term
2. Ever told has condition, still current but not long-term
3. Ever told has condition, not current.
Respondents without a condition are classified into category 5: Never told, not current or long-term.
An additional category '4: Not known or not ever told, but condition current and long-term' is also used in the 2014-15 NHS 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.
Condition prevalence is usually reported based on categories 1 and 4 (where applicable in NHS), 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, the 2014-15 NHS collected information on self-assessed health and
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 NHS. The detailed output classification used for NHS was developed by the ABS based on mapping between the 1000 input code list and ICD10 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 10TH REVISION OF THE INTERNATIONAL CLASSIFICATION OF DISEASES (ICD10)
was used in the development of this list, results are generally not available classified to the most detailed condition level based on ICD10. 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. Copies of the standard classifications of medical conditions available from the NHS
are contained in Appendix 2: Classification of medical conditions
Number of conditions
There are three data items available from the 2014-15 NHS relating to the number of conditions reported. They are:
- Number of conditions reported (includes any condition reported regardless of condition status)
- Number of current conditions reported (includes only conditions reported as current - the condition could also be long-term)
- Number of current long-term conditions reported (includes only conditions reported as current and long-term).
These items include any conditions which the respondent reported including any of the priority, targeted conditions, sight and hearing conditions, or other long-term conditions (e.g. hayfever, food allergies, migraines, back pain etc.) The condition did not have to be diagnosed (i.e. the respondent did not have to have been told by a doctor or nurse that they had the condition) for it to be included.
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.
- Although in the 2014-15 NHS 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 Disability sub-section, for more information.
- The prevalence of most long-term illness increases with age. In drawing comparisons of prevalence between NHS surveys, account should be taken of the shift in the age profile of the Australian population during the period between surveys. As a result of this, Table 1 National Health Survey: First Results, 2014-15 (cat. no. 4364.0.55.001) has been age standardised so that direct comparisons can be made.