Improving risk prediction for cardiovascular disease and type 2 diabetes in the general Australian population

Abstract

Cardiovascular disease (CVD) and type 2 diabetes are two major public health challenges. There is strong evidence that both conditions are predictable and preventable. Accurate identification of individuals at higher risk of CVD and type 2 diabetes is critical for the most effective and efficient prevention of these conditions, as it ensures preventive resources are focused on those who are most likely to benefit. Firstly, using baseline data from the nation-wide, population-based Australian Diabetes, Obesity and Lifestyle (AusDiab) study, this thesis examined how well the current Australian Pharmaceutical Benefits Scheme eligibility criteria for subsidy of lipid-lowering drugs identified individuals who were at high risk of developing CVD events according to the current national guidelines; and whether an anthropometric index can be used as an ancillary measure to help identify individuals with a high absolute cardiovascular risk estimate. Secondly, a validated risk prediction tool for future CVD mortality was developed based on recalibration of the SCORE (Systematic COronary Risk Evaluation) risk chart using Australian national mortality data and the major CVD risk factor profiles from eight Australian population-based surveys. Since diabetes is a major and independent risk factor for CVD, this thesis was expanded to include the prediction of risk of diabetes by analysing data from the two waves of the AusDiab study. Relevant work entailed development and validation of a self-completed, non-invasive Australian Type 2 Diabetes Risk Assessment Tool (AUSDRISK); and investigation of four different screening strategies to maximise efficiency of screening for people with a high risk of future diabetes and those with prevalent undiagnosed diabetes. The study found that: i) 11.0% of all Australian men and 3.6% of women aged 30-74 years old with neither CVD nor diabetes were found to be at high absolute CVD risk, and less than 20% of these high-risk individuals were being treated with lipid-lowering agents. Conversely many individuals eligible for statins subsidy were estimated to be at relatively low risk; ii) measurement of waist-to-hip ratio could be used as an ancillary measure to help identify individuals who are likely to have an increased absolute cardiovascular risk estimate; iii) an Australian risk prediction chart for CVD mortality was generated and validated, and offers an easy and simple approach to assessing 10-year risk of CVD death; iv) the AUSDRISK provides a valid and reliable method to estimate the 5-year risk of developing type 2 diabetes and is also able to identify asymptomatic individuals who are likely to have prevalent undiagnosed diabetes in cross-sectional settings; v) a sequential risk stratification strategy, using AUSDRISK then a second score incorporating fasting glucose, would maximise efficiency of type 2 diabetes screening and inform appropriate intervention. In conclusion, this work provides two validated tools for predicting risk of CVD mortality and incident type 2 diabetes, respectively. These tools will help improve strategies for detection of individuals at high risk of CVD or diabetes to ensure they might receive adequate prevention and treatment. The overall findings will help inform national health strategies and clinical practice related to the prevention and management of CVD and type 2 diabetes in Australia.