Impact of socioeconomic and risk factors on cardiovascular disease and type II diabetes in Australia: comparison of results from longitudinal and cross-sectional designs

OBJECTIVE: Existing large-scale studies do not take into account comorbidity or control for selection and endogeneity biases. This study addresses these shortcomings. PARTICIPANTS: We use information on individuals aged between 35 and 70 years from a nationally representative longitudinal survey conducted in Australia between 2001 and 2013. Participants were approached annually, and updates on their characteristics, including health status, were ascertained through self-reporting. METHOD: We develop three different analytical designs. The first model is a cross-sectional analysis against which our improved models are compared. In the second model, we follow the same approach but control for prior health conditions. The last preferred model additionally adjusts for characteristics and risk profile of respondents prior to onset of conditions. It also allows for comorbidity and controls for selection bias. RESULTS: Once comorbidity and changes over time in the participant's characteristics are controlled for, body mass index (BMI), alcohol consumption and physical activity exhibit a stronger impact than in the models without these controls. A unit increase in BMI increases the risk of developing a cardiovascular disease (CVD) condition within 2 years by 1.3 percentage points (β=0.11, 95% CI 0.05 to 0.16) and regular alcohol intake increases the risk of CVD by 3.0 percentage points (β=0.24, 95% CI 0.09 to 0.39). Both factors lose significance without proper control for endogenous behavioural change. We also note that frequent physical activity reduces the risk of developing diabetes by 0.9 percentage point (β=−0.40, 95% CI −0.72 to −0.07). CONCLUSIONS: Our result shows a greater importance of certain lifestyle and risk factors than was previously suggested.