Australian Bureau of Statistics
Celebrating the International Year of Statistics 2013

LONG-TERM HEALTH CONDITIONS


DEFINITION

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; and
• long-term or permanent impairments or disabilities.

POPULATION

Information was obtained for all persons in the NHS survey.

METHODOLOGY

Long-term condition data is drawn from two conceptually different sets of data:

• conditions that are specifically asked about in their own modules, including: asthma, cancer, heart and circulatory conditions, diabetes mellitus, kidney disease, arthritis, osteoporosis, and sight and hearing.
• conditions reported in response to the questions in the long-term conditions module on whether they currently had any other long-term health conditions which had lasted, or were expected to last, for six months or more.

Data from these two groups are combined into a condition status relating to long-term conditions or persons with long-term conditions, in the following 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.
4. Not known if ever told or not ever told, but condition current and long-term.
5. Never told, not current or long-term.

Specific condition modules

The 2011-12 NHS collected information on the prevalence of some long-term conditions in the Australian population via specific modules enabling particular questions to be asked about people with those conditions. Those conditions included those classified as National Health Priority Areas as well as sight and hearing. The National Health Priority Area conditions were:

• asthma;
• cancer;
• heart and circulatory conditions;
• diabetes;
• kidney disease;
• arthritis; and
• osteoporosis.

The prevalence of these conditions was established though the collection of supplementary information to determine whether a reported condition was current and long-term. Some conditions such as sight and hearing were assumed to be current and/or long term. This is discussed in more detail in the individual sections later in this chapter.

Long-term conditions module

Initial data for other long-term conditions was collected via a prompt card showing the following conditions. Respondents were asked whether they currently had any of these conditions, and whether they had lasted or were expected to last for six months or more:

• hayfever;
• sinusitis or sinus allergy;
• food allergy;
• drug allergy;
• other allergy;
• anaemia;
• bronchitis;
• emphysema;
• epilepsy;
• fluid problems/fluid retention/oedema (excluding those due to heart or circulatory conditions);
• hernias;
• kidney stones;
• migraine;
• psoriasis;
• stomach/other gastrointestinal ulcers;
• thyroid trouble/goiter;
• depression;
• feeling depressed;
• back - slipped disc or other disc problems; and,
• back pain or other problems.

More than one response was allowed.

Respondents who reported having a food or drug allergy were asked whether their reaction to food or drugs is:

• anaphylactic;
• non-anaphylactic;
• both; or,
• don't know.

An anaphylactic reaction is a severe form of allergic reaction which may be life threatening. It may affect the skin, respiratory system, gastrointestinal system and cardiovascular system. The anaphylactic reaction can be brought on by an allergy to certain foods, or the use of certain drugs or herbal medicines.

Respondents were then asked to report any other conditions (not included on the previous list or reported earlier in the survey) that had lasted or were expected to last six months or more. There was capacity to report up to six other conditions. If more than six conditions were identified the six main conditions were recorded.

Respondents were then finally asked whether they had any other long-term conditions such as the following:

• amputation or loss of limbs, e.g. arm, foot, finger;
• behavioural or emotional disorders;
• deformity or disfigurement from birth, e.g. club foot, cleft palate;
• other deformity or disfigurement, e.g. effects of burns;
• dependence on drugs or alcohol;
• difficulties in learning or understanding;
• feeling anxious or nervous;
• gallstones;
• incontinence;
• paraplegia or other paralysis; and,
• speech impediment.

More than one response was allowed.

For respondents who identified here that they had asthma, cancer, diabetes/high sugar levels, heart and circulatory disease, kidney disease, arthritis or osteoporosis, depending on question wording, an edit was triggered if they had not previously responded to their related module. Interviewers were then able to return to that module and complete it or progress to the question regarding whether they had ever been told by a doctor or nurse that they have that condition. This enabled most of these cases to be appropriately classified to a condition status which was derived for all conditions. If this edit was not triggered then diagnosis status was identified as not known and specific module questions were not answered.

Mental Health Conditions

Respondents who identified in this module having specific mental health conditions were asked an additional set of questions for each condition up to a limit of 6 conditions. These questions included:

• whether their mental health condition had been diagnosed by a doctor or nurse; and,
• at what age they were first told they had the mental health condition.

Respondents were then asked (whether or not they had been diagnosed) whether they had taken any of the following medications in the last two weeks for any of their conditions:

• sleeping tablets or capsules;
• tablets or capsules for anxiety or nerves;
• tranquillisers;
• antidepressants;
• mood stabilisers; or,
• other medications for mental health.

How long they had been taking each type of medication for:

• less than 1 month;
• 1 month to less than 3 months
• 3 months to less than 6 months
• 6 months or more; or,
• don't know.

The frequency they took each type of medication:

• every day and/or night
• more than 3 days and/or nights in a week;
• 1 to 3 days and/or nights a week
• less than once a week; or,
• varies/as required.

Respondents with a diagnosed mental health condition were then sequenced to the "Actions" module where they were asked questions about the number of times they had seen a GP, specialist etc. for their mental health condition.

Conceptually, cases of mis-diagnosis are excluded. Where interviewers became aware of a condition which the respondent had been told they have, but that diagnosis later proved incorrect, the respondent was recorded as not ever told they have the condition. This approach retains the conceptual alignment between the 'ever told' and 'whether current' populations. However, respondents may not have made this known to interviewers, with the result being that those cases will appear in survey results as 'ever told' but 'not current'.

The 2011-12 NHS questionnaire design enabled a theoretical maximum of 100 conditions per person to be reported. While the survey questionnaires were designed to prompt respondents and give them an opportunity to report all their long-term conditions, whether or not they chose to report a condition to the ABS interviewer, and how they chose to identify or describe that condition, was at the respondent's discretion.


INFORMATION ABOUT MEDICAL CONDITIONS

Classification of conditions

Provision was made on the survey questionnaires for interviewers to record condition information in two ways:

• record responses against predefined and specified condition type/name response categories; or
• select from a larger list contained in a trigram coder.

Information from both sources was combined and classified 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. 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.

Results from the survey 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. While some data at this level may be made available on request for more commonly occurring conditions, for general output purposes, long-term conditions are classified based on the 10TH REVISION OF THE INTERNATIONAL CLASSIFICATION OF DISEASES (ICD10). Refer to Appendix 2: Classification of medical conditions for the conditions classifications and codes used in the AHS.

The output classification 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; and,
• the variability of the descriptions of conditions provided by respondents.

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, where the precise condition name wasn't known at the time of the interview. Copies of the standard classifications of medical conditions available from this survey are contained in Appendix 2: Classification of medical conditions of this Users' Guide. The process of mapping the 1000 input codes to the ICD10 output classifications was complex, and in some cases the classification of the input codes was based on 'best fit' rather than 'exact match'.

INTERPRETATION

Points to be considered in interpreting data for this topic include the following:

• The data relate to conditions 'as reported' by respondents and hence do not necessarily represent conditions as medically diagnosed, except in the case of those conditions where respondents reported having been advised by a doctor or nurse that they had the condition. However, as the data relate to conditions which had lasted or were expected to last for six months or more, there is considered to be a reasonable likelihood that medical diagnoses would have been made in most cases. The degree to which conditions have been medically diagnosed is likely to differ across condition types.
• As the NHS is a household survey, residents of hospitals, nursing or convalescent homes or similar accommodation were outside the scope of the surveys, therefore prevalence data for conditions such as cancer are likely to be affected.
• While the methodology was aimed at maximising the identification of long-term conditions, some under-reporting may have occurred, particularly in respect of those conditions which are controlled by treatment (such as epilepsy) or recur infrequently, or those to which respondents have become accustomed and no longer consider an illness.
• Where conditions with specific modules are reported later in the survey (rather than in the specified section), the prevalence of that condition is still recorded appropriately. However, unless it has been identified that the condition is diagnosed, there will be no response to the questions asked within the condition module. If a diagnosis status is identified via another module or from triggering the question in the "Long-term conditions" module a 'not known' response will be recorded for condition-related data.
• 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 long-term/permanent disabilities were within the scope of long-term conditions, data from this section on long-term conditions 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" module, for more information.

COMPARABILITY TO 2007-08

Changes in community perceptions of illness and disability, together with changes in the identification and treatment of conditions (e.g. institutional versus community care) may have affected the degree to which certain conditions were reported in the survey.

The prevalence of most long-term illness increases with age. In drawing comparisons of prevalence between the 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 in this product has been age standardised so that direct comparisons can be made.

Food and drug allergies are new categories added to the list of conditions in the 2011-12 survey.

Kidney disease was collected in a specific module for the first time in the 2011-12 survey.

This section contains the following subsection :

Self-assessed health status

Asthma

Arthritis

Cancer

Heart and circulatory conditions

Diabetes mellitus

Kidney disease

Osteoporosis

Sight and hearing

Disability

Injuries

Bodily pain

Mental health and well-being

Female life stages

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