based on measured venous plasma glucose concentration classifications that are outlined in the (WHO 1999). Cardiovascular disease is defined as a positive response to the questions “Have you ever been treated for or suffered from any of the conditions: heart disease e.g. heart attack, angina, or a stroke”. The definition of labour force participation from the AusDiab survey is taken to be those who are either working or not working but not retired. In the survey 5% of men and women in the working age groups were not working but not retired.
Explanatory variables for participation were chosen based on the empirical labour supply literature and include age, age squared, education level, marital status, diabetes and cardiovascular disease status. Explanatory variables for the two chronic disease equations -weight, exercise, hypertension and lipid levels, and family history of diabetes - were chosen on the basis of clinical literature on risk. A number of additional variables were initially considered e.g. past smoking, undiagnosed hypertension, untreated elevated lipid levels, overweight, and some exercise but jointly rejected on the theoretical basis that they were correlated with the included variables but less likely to have a direct impact on morbidity. The joint significance of these additional variables was rejected by an adjusted Wald test.
Table 1 shows mean values for the main determinants of labour supply and the key risk factors for diabetes and cardiovascular disease in the sample. The average age was 47 years for men and 49 years for women. Forty-seven percent of men and 36.0% of women had a University degree. This is high compared to the general population of Australia and suggests some potential bias in so far as we might expect a somewhat greater attachment to the labour force in this sample than population as a whole. The survey illustrates the high prevalence of disease risk factors for chronic disease in the population. For example as measured by waist circumference 26.7% of men and 33.6% of women were obese. Waist circumference provides an measure of overweight that is reasonably well correlated with the more common body mass index (BMI) as weight in kilograms divided by height in metres squared (Lean, Han et al. 1995), but appears to be a better indicator of type 2 diabetes and cardiovascular disease (Haffner, Stern et al. 1987). Almost half of men (42.4%) and more than half of women (52.8%) did not get sufficient exercise to maintain their health, while smoking was more common in men (19.1% smoked) compared to women (13.7% smoked).
Chronic disease and labour force participation in Australia: an endogenous multivariate probit analysis of clinical prevalence data