COHORT PROFILE Cohort Profile: The Fremantle Diabetes Study

When the Fremantle Diabetes Study (FDS) Phase I was conceived in 1991 by its chief investigator (T.M.E.D.), there were few published longitudinal communitybased diabetes natural history studies. Population studies such as Framingham in the United States and Busselton in Australia contained relatively small subgroups from which limited additional diabetesspecific information was collected. The United Kingdom Prospective Diabetes Study (UKPDS) had recruited more than 5000 newly diagnosed type 2 subjects aged 25–65 years but the sample, although relatively large, was not community based. The diagnosis of diabetes was based on a low fasting plasma glucose concentration (46 mmol/l), and the study was interventional with outcomes presented in 1998. There were also Australia-specific aspects of diabetes that had not been characterized in detail, especially the disproportionately large number of patients from a migrant (especially Southern European) background and the important question of diabetes in indigenous groups. The aim of FDS Phase I was, therefore, to identify from all potential sources, and collect detailed prospective data from, known diabetic patients in a stable multi-ethnic urban Australian population to examine clinically relevant aspects of diabetes including clinical management, metabolic control, complications and cost. Based on the amount of available seeding funding from the Raine Foundation, University of Western Australia (WA) and respecting a reasonable patient time commitment and throughput, it was decided to attempt to recruit all consenting patients from the Fremantle Hospital (FH) primary catchment area, a postcode-defined population of approximately 120 000 living in and around the port of Fremantle in Western Australia. A 3-year registration period between 1993 and 1996 was followed by yearly reviews of the FDS Phase I cohort until 2001 (a minimum follow-up of 5 years) by which time more than half of the patients had died or withdrawn, although acquisition of hospitalizations, cancer registrations and deaths through the WA Data Linkage System (WADLS) has continued since. During and after the active data collection in Phase I, the results of a number of studies were published that provided important data relating to diabetes epidemiology and management. The Australian Diabetes, Obesity, and Lifestyle (AusDiab) Study showed that the prevalence of diabetes had increased at the rate of 0.15%/year in males and 0.18%/year in females in individuals aged 525 years during the 19 years since the first Australian estimate from the Busselton survey in 1981. The incidence of type 1 diabetes in Australia was also increasing. A contributor to this increased prevalence was the lowering of the threshold fasting plasma glucose for diagnosis of diabetes from 7.8 mmol/l to 7.0 mmol/l by the World Health Organization in 1999. In relation to management, results of the Diabetes Control and Complications Trial (DCCT) in type 1 diabetes were first presented in 1993 and confirmed the benefits of tight glycaemic control in the prevention of microvascular disease. Parallel findings for type 2 diabetes from the UKPDS followed in 1998 but the UKPDS also highlighted the vascular benefits of intensive management of hypertension. Other landmark non-glycaemic intervention trials, such as the Heart Outcomes Prevention Evaluation (HOPE and MICRO-HOPE), the Heart Protection Study and the Fenofibrate Intervention and Event Lowering in Diabetes Study provided further evidence of the benefits of individual intensive vascular risk factor management in type 2 diabetes. The Steno-2 Study extended these findings in a multifactorial intervention that reduced both microand macrovascular disease. In addition, the 33% 2-year mortality rate in conventionally treated diabetic patients after myocardial infarction in the Diabetes Mellitus, Insulin Glucose Infusion in Acute Myocardial Infarction (DIGAMI) Study carried out in the early 1990s had fallen to 19% in similar patients in the more recent DIGAMI-2 Study in the presence of increased Published by Oxford University Press on behalf of the International Epidemiological Association