Identifying and definitional attributes
|Metadata item type:||Quality Statement|
|Registration status:||Health, Superseded 12/03/2015|
|Indicators linked to this Quality statement:|
National Healthcare Agreement: P05-Proportion of persons obese, 2010 Health, Superseded 08/06/2011
|Institutional environment:||The National Health Survey (NHS) and the National Aboriginal and Torres Strait Islander Survey (NATSIHS) are collected, processed, and published by the Australian Bureau of Statistics (ABS). The ABS operates within a framework of the Census and Statistics Act 1905 and the Australian Bureau of Statistics Act 1975. These ensure the independence and impartiality from political influence of the ABS, and the confidentiality of respondents. For more information on the institutional environment of the ABS, including the legislative obligations of the ABS, financing and governance arrangements, and mechanisms for scrutiny of ABS operations, please see ABS Institutional Environment.|
The NHS is conducted every three years over a 12 month period. Results from the 2007-08 NHS were released in May 2009.
The NATSIHS is conducted every six years. Results from the 2004-05 survey were released in April 2006.
|Accessibility:||See National Health Survey, Summary of Results (cat. no. 4364.0) for an overview of results from the NHS, and National Health Survey: State tables (cat. no. 4362.0) for State and Territory specific tables. See the National Aboriginal and Torres Strait Islander Health Survey (cat. no. 4715) for an overview of results from the NATSIHS. Other information from these surveys is also available on request.|
Information to aid interpretation of the data is available from the National Health Survey User Guide, and the National Aboriginal and Torres Strait Islander Health Survey User Guide on the ABS website.
Many health-related issues are closely associated with age, therefore data for this indicator have been age-standardised to the 2001 total Australian population to account for differences in the age structures of the States and Territories and the Indigenous and non-Indigenous population. Age standardised rates should be used to assess the relative differences between groups, not to infer the rates that actually exist in the population.
The 2007-08 NHS collected measured height and weight from persons aged 5 years and over, and self-reported height and weight from persons aged 15 years and over. For the purposes of this Indicator, Body Mass Index (BMI) values are derived from measured height and weight information using the formula: weight (kg) / height (m)2. Data for Indigenous persons are based on self-reported height and weight, from the 2004-05 NHS and 2004-05 NATSIHS.
Despite some limitations, BMI is widely used internationally as a relatively straightforward way of measuring obesity.
The NHS is conducted in all States and Territories, excluding very remote areas. Non-private dwellings such as hotels, motels, hospitals, nursing homes and short-stay caravan parks were also not included in the survey. The exclusion of persons usually resident in very remote areas has a small impact on estimates, except for the Northern Territory, where such persons make up a relatively large proportion of the population. The 2007-08 NHS response rate was 91 per cent. NHS data are weighted to account for nonresponse.
The NATSIHS is conducted in all states and territories and includes remote and non-remote areas. The 2004–05 sample was 10,000 persons/5,200 households, with a response rate of 81 per cent of households.
As it is drawn from a sample survey, the indicator is subject to sampling error. Sampling error occurs because only a small proportion of the population is used to produce estimates that represent the whole population. Sampling error can be reliably estimated as it is calculated based on the scientific methods used to design surveys. Rates should be considered with reference to their Relative Standard Error (RSE). Estimates with RSEs between 25 per cent and 50 per cent should be used with caution. Estimates with RSEs greater than 50 per cent are generally considered too unreliable for general use.
RSEs for adult obesity rates for Remote areas are all greater than 25 per cent and should be used with caution. The rate for Tasmania is greater than 50 per cent. The breakdown by SEIFA quintiles has sampling error within acceptable limits, except for the Northern Territory. For children, remoteness and SEIFA disaggregations by state/territory are generally unreliable and national level figures should be used with caution.
Adult obesity rates by age and sex should be used with caution at the State/Territory level, but generally have acceptable levels of sampling error at the national level and for total adults. State breakdowns for children are generally greater than 25 per cent RSE with many cells above 50 per cent and should not be considered reliable. Age by sex breakdowns at the national level are within acceptable limits.
Sampling errors for BMI data for all persons by state/territory are generally within acceptable limits, though figures for Tasmania (particularly for children) should be used with caution.
BMI data for children aged 15-17 years by Indigenous status was not able to be included as the small sample size meant that the data was of very poor quality.
The methods used to construct the indicator are consistent and comparable with other collections and with international practise.
Most surveys, including CATI health surveys conducted by the states and territories, collect only self-reported height and weight. There is a general tendency across the population for people to overestimate height and underestimate weight, which results in BMI scores based on self-reported height and weight to be lower than BMI scores based on measured height and weight.
The age- and sex-specific cutoff points for BMI categories for children are from the work of Cole TJ, Bellizzi MC, Flegal KM & Dietz WH 2000, “Establishing a standard definition for child overweight and obesity worldwide: international survey”, BMJ 320:1240.
The NHS and NATSIHS collect a range of other health-related information that can be analysed in conjunction with BMI.
Source and reference attributes
|Submitting organisation:||Australian Bureau of Statistics|
|Related metadata references:|
Has been superseded by National Healthcare Agreement: PI 03-Prevalence of overweight and obesity, 2013 QS Health, Superseded 14/01/2015