The Australian Diabetes, Obesity and Lifestyle Study (AusDiab)—methods and response rates

doi:10.1016/S0168-8227(02)00025-6

Diabetes Research and Clinical Practice

Volume 57, Issue 2, August 2002, Pages 119-129

https://doi.org/10.1016/S0168-8227(02)00025-6 Get rights and content

Abstract

The Australian Diabetes, Obesity and Lifestyle Study (AusDiab) addresses the urgent need for data on diabetes prevalence, risk factors and associated conditions in Australia. Here we describe the methods used and the response rates obtained. AusDiab was a population-based cross-sectional survey of national diabetes mellitus prevalence and associated risk factors in people aged ⩾25 years, conducted between May 1999 and December 2000 in the six states and the Northern Territory of Australia. The study involved an initial household interview, followed by a biomedical examination that included an oral glucose tolerance test (OGTT), standard anthropometric tests, blood pressure measurements and the administration of questionnaires. Of the 20 347 eligible people (aged ⩾25 years and resident at the address for ⩾6 months) who completed a household interview, 11 247 (55.3%) attended for the biomedical examination. Of those who completed the biomedical examination 55.1% were female. Comparisons with the 1998 Australian population estimates showed that younger age responders were under-represented at the biomedical examination, while the middle-aged and older age groups were over-represented. Weighting of the AusDiab data for age and gender have corrected for this bias. AusDiab, which is the largest national diabetes prevalence study undertaken in a developed nation to have used an OGTT, provides a valuable national resource for the study of the prevalence and possible causes of diabetes, as well as identifying possible risk factors that may lead to diabetes. Furthermore, it generates the baseline data for a prospective 5-year cohort study. The data will be important for national and regional public health and lifestyle education and health promotion programs.

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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The Australian Diabetes, Obesity and Lifestyle Study (AusDiab)—methods and response rates

Abstract

Introduction

Section snippets

Target population/eligibility requirements

Sampling frame

Survey response

Discussion

Acknowledgements

The rising global burden of diabetes and its complications: estimates and projections to the year 2010

Diabetic Med.

Global burden of diabetes, 1995–2025. Prevalence, numerical estimates and projections

Diabetes Care

Prevalence of impaired fasting glucose, and impaired glucose tolerance in US adults. The Third National Health and Nutrition Examination 1988–1994

Diabetes Care

Diabetes and impaired glucose tolerance. A prevalence estimate based on the Busselton 1981 survey

Med. J. Aust.