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4364.0 - National Health Survey: Summary of Results, 2001  
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 25/10/2002   
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INTRODUCTION

1 This publication presents results from the National Health Survey (NHS) which was conducted throughout Australia from February to November 2001. This is the fifth in the series of health surveys conducted by the ABS; previous surveys were conducted in 1977-78, 1983, 1989-90 and 1995.

2 The survey collected information about:

  • the health status of the population, including long term medical conditions experienced and recent injuries
  • use of health services such as consultations with health practitioners and visits to hospital and other actions people have recently taken for their health
  • health related aspects of people's lifestyles, such as smoking, diet, exercise and alcohol consumption
  • demographic and socioeconomic characteristics.

3 The statistics presented in this publication are a selection of the information available. Some emphasis has been given in this publication to providing information on National Health Priority Areas.

4 A supplementary health survey of Aboriginal and Torres Strait Islander people was conducted in association with the 2001 NHS. Information about that survey, together with summary results will be separately published in National Health Survey 2001: Aboriginal and Torres Strait Islander Results, Australia (cat. no. 4715.0).


SCOPE OF THE SURVEY

5 The NHS was conducted in a sample of 17,918 private dwellings across Australia. Both urban and rural areas in all states and territories were included, but sparsely settled areas of Australia were excluded. Non private dwellings such as hotels, motels, hostels, hospitals, nursing homes and short-stay caravan parks were not included in the survey.

6 Within each selected household, a random sub-sample of usual residents was selected for inclusion in the survey as follows:
  • one adult (18 years of age and over)
  • all children aged 0-6 years
  • one child aged 7-17 years.

7 Subsampling of respondents enabled more information to be collected from each respondent than would have been possible had all usual residents of selected dwellings been included in the survey.

8 The following groups were excluded from the survey:
  • certain diplomatic personnel of overseas governments, customarily excluded from the Census and estimated resident population figures
  • persons whose usual place of residence was outside Australia
  • members of non-Australian defence forces (and their dependants) stationed in Australia
  • visitors to private dwellings.


DATA COLLECTION

9 Trained ABS interviewers conducted personal interviews with selected residents of sampled dwellings. One person aged 18 years and over in each dwelling was selected and interviewed about their own health characteristics. An adult resident, nominated by the household, was interviewed about all children aged 0-6 years and one selected child aged 7-17 years in the dwelling. Adult female respondents were invited to complete a small additional questionnaire covering supplementary women's health topics.


SURVEY DESIGN

Sample size and selection

10 Dwellings were selected at random using a multi-stage area sample of private dwellings. The initial sample selected for the survey consisted of approximately 21,900 dwellings; this reduced to a sample of approximately 19,400 after sample loss (e.g. households selected in the survey which had no residents in scope for the survey, vacant or derelict buildings, buildings under construction). Of those remaining dwellings, around 92% were fully responding, yielding a total sample for the survey of 26,863 persons.

11 To take account of possible seasonal effects on health characteristics, the sample was spread throughout the 10 months enumeration period. Conduct of the survey was suspended during the six weeks from 28 July to 10 September during the Census of Population and Housing enumeration period.

12 At the request of the relevant health authorities:
  • the sample in the Northern Territory (NT) was reduced to a level such that NT records contribute appropriately to national estimates but cannot support reliable estimates for the NT. This was requested to enable a larger NT sample to be used in the General Social Survey conducted by the ABS in 2002. As a result, estimates for NT are not shown separately in this publication.
  • the sample in the Australian Capital Territory was increased by around 60% to improve the reliability of estimates.


WEIGHTING, BENCHMARKING AND ESTIMATION

Weighting

13 Weighting is the process of adjusting results from a sample survey to infer results for the total population. To do this, a 'weight' is allocated to each sample unit. The weight is a value which indicates how many population units are represented by the sample unit.

14 The first step in calculating weights for each person was to assign an initial weight, which was equal to the inverse of the probability of being selected in the survey. For example, if the probability of a person being selected in the survey was 1 in 600, then the person would have an initial weight of 600 (that is, they represent 600 others).

Benchmarking

15 The weights were calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks', in designated categories of sex by age by area of usual residence categories. Weights calibrated against population benchmarks compensate for over or under-enumeration of particular categories of persons and ensure that the survey estimates conform to the independently estimated distribution of the population by age, sex and area of usual residence, rather than to the distribution within the sample itself.

16 The survey was benchmarked to the estimated population living in private dwellings in non-sparsely settled areas at 30 June 2001 based on results from the 2001 Census of Population and Housing. Hence the benchmarks relate only to persons living in private dwellings, and therefore do not (and are not intended to) match estimates of the total Australian resident population (which include persons living in non-private dwellings, such as hotels) obtained from other sources.

Estimation

17 Survey estimates of counts of persons are obtained by summing the weights of persons with the characteristic of interest. Estimates of non-person counts (e.g. days away from work) are obtained by multiplying the characteristic of interest with the weight of the reporting person and aggregating.

Standardisation

18 Data for states and the ACT and most time series data contained in this publication are shown as age (and sex) standardised estimates or percentages. Many health characteristics are age-related and to enable comparisons over time or across population groups (e.g. between states) the age profile of the populations being compared needs to be considered. The age standardised percentages are those which would have prevailed should the actual population have the standard age composition. In this publication the standard population is the benchmark population; i.e. the population at 30 June 2001 based on the 2001 Census of Population and Housing, adjusted for the scope of the survey. It should be noted that minor discrepancies in totals may occur between standardised and non-standardised estimates or percentages, as a result of the standardisation process.


RELIABILITY OF ESTIMATES

19 The estimates provided in this publication are subject to sampling and non-sampling error.

Sampling error

20 Sampling error is the difference between the published estimates, derived from a sample of persons, and the value that would have been produced if all persons in scope of the survey had been included. For more information refer to the Technical Notes. In this publication, estimates with a relative standard error of 25% to 50% are preceded by an asterisk (e.g. *3.4) to indicate that the estimate should be used with caution. Estimates with a relative standard error over 50% are indicated by a double asterisk (e.g. **0.6) and should be considered unreliable for most purposes.

Non-sampling error

21 Non-sampling error may occur in any data collection, whether it is based on a sample or a full count such as a Census. Sources of non-sampling error include non-response, errors in reporting by respondents or recording of answers by interviewers, and errors in coding and processing data.

22 Non-response occurs when people cannot or will not cooperate, or cannot be contacted. Non-response can affect the reliability of results and can introduce a bias. The magnitude of any bias depends upon the rate of non-response and the extent of the difference between the characteristics of those people who responded to the survey and those who did not.

23 The following methods were adopted to reduce the level and impact of non-response:
  • face-to-face interviews with respondents
  • the use of interviewers who could speak languages other than English where necessary
  • follow-up of respondents if there was initially no response
  • weighting to population benchmarks to reduce non-response bias.

24 By careful design and testing of questionnaires, training of interviewers, asking respondents to refer to records where appropriate, and extensive editing and quality control procedures at all stages of data processing, other non-sampling error has been minimised. However, the information recorded in the survey is essentially 'as reported' by respondents, and hence may differ from information available from other sources, or collected using different methodology. In particular it should be noted that:
  • information about medical conditions was not medically verified and most was not necessarily based on diagnosis by a medical practitioner. Conditions which have a greater effect on people's wellbeing or lifestyle, or those which were specifically mentioned in survey questions are expected in general to have been better reported than others
  • results of previous surveys have shown a tendency for respondents to under-report alcohol consumption levels and their weight, but over-estimate their height
  • respondents were asked to refer to children's immunisation records and to medication packets/bottles when answering related questions. However, this was not possible in all cases, which may have reduced the reliability of some information reported
  • in this survey immunisation status is derived from counts of the number of vaccinations of various types reported as being received. As the cumulative number of vaccinations required increases with age, the likelihood of reporting error may also increase, with the result that immunisation status of older children may be less reliable than for younger children.


CLASSIFICATIONS

Long term medical conditions

25 All reported long term medical conditions were coded to a list of approximately 1,000 condition categories which was prepared for this survey. Information about medical conditions classified at this level of detail will not generally be available for output from the survey; however, they can be regrouped in various ways for output. Three standard output classifications developed by the ABS for this survey are available:
  • a classification based on the International Classification of Diseases, 10th revision (ICD10)
  • a classification based on the 2 plus edition of the International Classification of Primary Care (ICPC)
  • a classification based on the International Classification of Diseases, 9th revision (ICD9), which is similar to the classification of conditions used in the 1995 NHS, and has been retained to assist data users in comparing 2001 and 1995 results.

26 In this publication, medical conditions data from the 2001 NHS are shown classified to the ICD10-based classification, or variants of that classification. Data from the 1989-90 and 1995 surveys are classified to the ICD9: although different classifications are used, conditions selected for inclusion in the publication were generally those where classification differences would have minimal impact on comparability. However, classification differences do reduce direct comparability for the categories complete/partial hearing loss, rheumatism and heart disease.

Pharmaceutical medications

27 Pharmaceutical medications reported by respondents as used for asthma, diabetes mellitus/high sugar levels, cardiovascular conditions or cancer were classified into generic types. The classification used was developed by the ABS for this survey, but is based on the WHO Anatomical Therapeutic Chemical (ATC) classification, and the framework (based on organ system and therapeutic drug class) underlying the listing of medications in the Australian Medicines Handbook.

Demographic characteristics

28 Country of Birth was classified according to the Standard Australian Classification for Countries.

29 Languages spoken at home were classified according to the Australian Standard Classification of Languages.

Geographic characteristics

30 In this publication, survey results are shown compiled for Australia, individual states and the ACT, and broad categories from the Australian Standard Geographical Classification (ASGC) Remoteness Area classification. Results compiled at other levels of the ASGC can be compiled on request.


RESULTS OF THE SURVEY

Comparability with previous National Health Surveys

31 Summary results of the last two NHSs were published in National Health Survey, Summary of Results, Australia, 1989-90 and 1995 (cat. no. 4364.0). A range of other publications was also released from each of these surveys; see paragraph 39.

32 This publication contains some results from the last two NHSs, the 1995 Children's Immunisation and Health Screening Survey and the 1997 Survey of Mental Health and Wellbeing of Adults. Understanding the comparability of data from the 2001 NHS with data from these other surveys is crucial to the use of the data and interpretation of apparent changes in health characteristics over time. While the 2001 NHS is similar in many ways, particularly to the 1995 NHS, there are important differences in sample design and coverage, survey methodology and content, definitions and classifications. These will effect the degree to which data are directly comparable between the surveys.

33 The main differences between the 1995 and 2001 NHSs which may effect comparability of data presented in this publication are shown below. In this publication, data from previous surveys are only shown where a reasonable level of comparability exists.
  • While the number of dwellings sampled was slightly smaller in 2001, sub-sampling of persons within households has meant the number of persons sampled in 2001 was about half that in 1995 (in which several states purchased additional sample). This has reduced the reliability of some estimates.
  • The sample for the 1995 survey included some non-private dwellings and covered sparsely settled areas. The 2001 NHS survey included private dwellings in urban and rural areas only. However, both the sparsely settled and special dwelling populations are quite small and hence their exclusion in 2001 is regarded as having minimal impact on comparability, particularly at the data levels shown in this publication.
  • All persons in sampled dwellings were included in the 1995 survey, and only records from fully responding households were retained on the data file. In contrast the 2001 survey sub-sampled persons within households (one adult, all children 0-6 years, one child 7-17 years). To the extent that some health characteristics may be clustered within households, the different sampling approaches may impact slightly on comparability between surveys.
  • The 2001 survey was effectively enumerated over about a ten month period, compared with a 12 month period for the 1995 survey. The 2001 survey was not enumerated in December or January, nor during a 6 week period mid-winter (coinciding with conduct of the 2001 Census of Population and Housing).
  • Data relating to asthma, cancer and cardiovascular conditions were collected in detailed topic-specific question modules in 2001, whereas in 1995 the topics were covered in the context of general long term conditions. There is expected to be a greater tendency among respondents to report conditions in response to direct questions rather than in response to more general questions.
  • Data relating to asthma, cancer, cardiovascular conditions and diabetes/high sugar levels were primarily collected through questions which screened out conditions which had not been medically diagnosed. This was not the case in the 1995 survey. Although the data are therefore conceptually different for these items between surveys, the nature of the conditions involved is such that most cases reported in the 1995 survey are expected to have been medically diagnosed and therefore effects on the comparability of data are expected to be relatively small.
  • The coding systems and classifications used for long term conditions, type of medication and alcohol consumption differed between surveys.
  • Data about cause of long term conditions i.e. whether work-related or due to an injury, are conceptually different between surveys and therefore are not directly comparable.
  • Injuries data obtained in the 2001 NHS related to injury events occurring in the 4 weeks prior to interview. In the 1995 survey injuries data referred to injuries current at the time of the survey irrespective of how long ago they occurred. As a result of these conceptual differences injuries data from the 2001 survey are not comparable with 1995 data.
  • Use of medications (including vitamins, minerals, natural and herbal medicines) was obtained only for specific conditions in the 2001 survey; the 1995 survey obtained data about all medication use, but included data on reasons (i.e. medical conditions) for use. At the condition level, therefore, data are considered broadly comparable but some care should be taken in making comparisons because of the different methodologies used in their collection.
  • The coverage of other health professionals (OHPs) has expanded with each NHS. Data about consultations with audiologists, hypnotherapists, occupational therapists and speech therapists were first collected in the 1995 survey. Aboriginal health worker (n.e.c.), accredited counsellor and alcohol and drug worker (n.e.c.) consultations were introduced in 2001. As a result data for consultations with OHPs at the aggregate level are not directly comparable although the expanded coverage in part reflects expanded use of OHPs.
  • Children's immunisation was not covered in 1995 NHS but in a separate survey conducted in April 1995. The methodologies used were similar, but questions were updated for the 2001 survey to reflect changes in the Standard Childhood Immunisation Schedule. Care should be taken in comparing data across surveys to ensure that changes to the schedule have been taken into account.
  • National information on psychological distress using the Kessler 10 Scale (K10) was first collected in the Survey of Mental Health and Wellbeing of Adults (SMHWB) conducted by the ABS in 1997. The SMHWB was an initiative of, and funded by, the Commonwealth Department of Health and Family Services as part of the National Mental Health Strategy. The K10 was included in the 2001 NHS as it proved to be a better predictor of depression and anxiety disorders than the other short, general measures used in the 1997 SMHWB.

34 As a result of the points above, some care should be taken in interpreting apparent changes over time in the prevalence of certain long term conditions and other health characteristics. Some movements between 1995 and 2001 estimates can, at least in part, be attributed to conceptual, methodological and/or classification differences. However, there are some instances where the degree or nature of the change suggests other factors are contributing to the movements, including changes in community awareness or attitudes to certain conditions, changes in common terminology for conditions, improvements in the diagnosis of certain conditions, etc. The degree of change attributable to all these factors, relative to actual change in the prevalence of characteristics, cannot be determined from information collected in this survey.

35 Further information about comparability between surveys will be contained in National Health Survey, Users' Guide, Australia, 2001 to be available through this site from December 2002. In addition, the ABS can offer advice, if required, on the comparison of the 2001 survey results with those from the 1995 or earlier surveys.


HEALTH PRODUCTS AND SERVICES

Results for states and territories

36 Summary results from this survey compiled separately for each state and the ACT are available in tabular form on this site or on request to ABS.

Microdata

37 For users who wish to undertake more detailed analysis of the survey data, it is expected that a confidentialised unit record file will be available on CDROM towards the end of 2002. Arrangements for other access to confidentialised microdata are also being developed and are expected to be in place by the end of 2002. Those wishing to access such microdata should contact the Director, Health Section of the ABS.

Special tabulations

38 Special tabulations are available on request. Subject to confidentiality and sampling variability constraints, tabulations can be produced from the survey incorporating data items, populations and geographic areas selected to meet individual requirements. These can be provided in printed or electronic form. A list of data items available from the survey is available free of charge on this site. Further information about the survey and associated products is available from the contact officer listed at the front of this publication.


RELATED PUBLICATIONS

39 Other ABS publications which may be of interest are shown below. Most of these are available on this site:

National Health Survey, Summary of Results, Australia, 1989-90 and 1995, cat. no. 4364.0

National Health Survey, Summary Results, Australian States and Territories, 1995, cat. no. 4368.0

National Health Survey, Users' Guide, 1989-90 and 1995, cat. no. 4363.0

National Health Survey, Private Health Insurance, 1995, cat. no. 4334.0

National Health Survey: Diabetes, Australia, 1995, cat. no. 4371.0

National Health Survey: Cardiovascular and Related Conditions, Australia, 1995, cat. no. 4372.0

National Health Survey: Asthma and Other Respiratory Conditions, Australia, 1995, cat. no. 4373.0

National Health Survey: Injuries, Australia, 1995, cat. no. 4384.0

National Health Survey: SF36 Population Norms, Australia, 1995, cat. no. 4399.0

Mental Health and Wellbeing: Profile of Adults, Australia, 1997, cat. no. 4326.0

Mental Health and Wellbeing: Users' Guide, 1997, cat. no. 4327.0

National Nutrition Survey: Selected Highlights, Australia, 1995, cat. no 4802.0

National Nutrition Survey: Foods Eaten, Australia, 1995, cat. no 4804.0

National Nutrition Survey: Nutrient Intakes and Physical Measurements, Australia, 1995, cat. no 4805.0

National Nutrition Survey: Users' Guide, 1995, cat. no 4801.0

Children's Health Screening, Australia, 1995, cat. no. 4337.0

Children's Immunisation, Australia, 1995, cat. no. 4352.0

Disability, Ageing and Carers, Summary of Findings, Australia, 1998, cat. no. 4430.0

40 Current publications and other products released by the ABS are listed in the Catalogue of Publications and Products (cat. no. 1101.0). The Catalogue is available from any ABS office or the ABS web site. The ABS also issues a daily Release Advice on the web site which details products to be released in the week ahead.


ABBREVIATIONS

ABSAustralian Bureau of Statistics
ARIAAccessibility/Remoteness Index of Australia
ASGCAustralian Standard Geographical Classification
ATCCAnatomical Therapeutic Chemical Classification
BMIBody mass index
cmCentimetres
GPGeneral medical practitioner
HibHaemophilus influenza type b
HRTHormone replacement therapy
HSLHigh sugar level
ICDInternational Classification of Diseases
ICPCInternational Classification of Primary Care
K10Kessler Psychological Distress Scale-10
kgKilogram
MMRMeasles mumps and rubella
n.e.c.Not elsewhere classified
NHMRCNational Health and Medical Research Council
NHSNational Health Survey
OHPOther health professional
RSERelative standard error
SEStandard error
SEIFASocio Economic Indexes for Areas
SMHWBSurvey of Mental Health and Wellbeing
WHOWorld Health Organisation




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