The Australian Diabetes, Obesity and Lifestyle Study (AusDiab)—methods and response rates
Introduction
Globally, the prevalence of diabetes, particularly Type 2 diabetes is rapidly increasing [1]. Indeed, it has been predicted that the global figure of people with diabetes will rise from current levels of about 150 million in 2000 to 300 million by 2025 [2]. However, with the exception of the USA [3], nationally representative, population based diabetes prevalence data among developed nations is scarce. In particular, few studies have involved an oral glucose tolerance test (OGTT).
In Australia, estimates of diabetes prevalence and other categories of glucose intolerance are confined to studies conducted 10–20 years ago on a small sample of residents from a rural town in Western Australia [4]. Most recent estimates of diabetes prevalence in Australia have relied on self-reported data, but since Type 2 diabetes can be asymptomatic for many years before it is diagnosed in a clinical situation, reliance on self-reported information invariably contributes to an underestimation of the true prevalence. Furthermore, such studies fail to provide information on the extent of other states of glucose intolerance, which are known to substantially increase risk of future diabetes.
To address the urgent need for more definitive data on the true current prevalence of diabetes and its associated risk factors in Australia, the Australian Diabetes, Obesity and Lifestyle Study (AusDiab) was a cross-sectional study involving a standard OGTT conducted during 1999–2000 in all Australian States and the Northern Territory. The present paper provides a detailed description of the survey methods including the design, sampling techniques and survey protocols. Data on weighting of the sample, response rates and statistical techniques are also presented. The survey methods conform to those recommended by the World Health Organisation (WHO) [5], and the study was approved by the International Diabetes Institute ethics committee.
The AusDiab study aimed to determine the national prevalence of diabetes and other selected non-communicable diseases and their risk factors in a representative sample of adults aged 25 years and over from each of the states and the Northern Territory of Australia.
More specifically, the objectives of the study were to:
- 1
estimate the national and regional prevalence of diabetes and other forms of abnormal glucose tolerance;
- 2
estimate the prevalence of the cardiovascular risk factors within the Metabolic Syndrome, including obesity, hypertension, and lipid profile abnormalities;
- 3
assess the distribution and relationships of the cardiovascular risk factors indicated above;
- 4
assess temporal trends in risk factor prevalences with reference to previous Australian surveys;
- 5
describe health knowledge and attitudes and utilization of health services, and
- 6
provide baseline data for longitudinal cohort studies.
Section snippets
Target population/eligibility requirements
Non-institutionalised adults aged 25 years and over residing in private dwellings in each of the six states and the Northern Territory of Australia were included in the survey if they had resided permanently at the address for a minimum of 6 months prior to the survey. Persons with physical or intellectual disabilities that precluded participation in the study were not included.
Sampling frame
A stratified cluster sampling method was used, involving seven strata (six states and the Northern Territory) and
Survey response
Response rates to the household interview and the biomedical examination are shown in Fig. 1. In total, the AusDiab interviewers approached 25 984 households in the 42 selected clusters. Of these, 6769 (26%) were classified as non-contacts. Reasons for non-contact (and hence non-participation) in the household interview included language difficulties (318 households), no access gained to the residence (e.g. because of dangerous dogs, security fences) (941), the householders not being
Discussion
AusDiab is the largest cross-sectional study of the prevalence of diabetes and its precursors ever performed in a developed nation. Through its capacity to provide the first definitive data on the true magnitude of the diabetes epidemic in Australia, AusDiab will not only be a valuable resource for health care planners in Australia, but will also serve as an important research tool for the study of diabetes and associated diseases on a longitudinal basis.
The AusDiab experience provides a
Acknowledgements
We are most grateful to the following for their support of the study: The Commonwealth Department of Health and Aged Care, Eli Lilly (Aust) Pty Ltd, Janssen–Cilag (Aust) Pty Ltd, Knoll Australia Pty Ltd, Merck Lipha s.a., Alphapharm Pty Ltd, Merck Sharp & Dohme (Aust), Roche Diagnostics, Servier Laboratories (Aust) Pty Ltd, SmithKline Beecham International, Pharmacia and Upjohn Pty Ltd, BioRad Laboratories Pty Ltd, HITECH Pathology Pty Ltd, the Australian Kidney Foundation, Diabetes Australia
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