Figures and tables in Economic modelling of the prevention of type 2 diabetes in Australia – the diabetes model

Abstract

This paper outlines the development of the Diabetes Model which projects the number of Australians 25 years of age and over who are expected to have pre-diabetes and type 2 diabetes over a 45 year simulation period. The model also simulates control of the disease in terms of glycaemic levels, cholesterol levels, weight and blood pressure control. The model produces a wide range of epidemiological and economic outputs to assess the current and projected impact of those with the disease. The number and cost of complications associated with type 2 diabetes, conditioning on the level of diabetes control, are also projected.

The model also provides the capacity to quantify the effect of hypothetical public health initiatives in the management of type 2 diabetes and associated trends in risk factor prevalence and diabetes control over the simulation period. While the benefits of such programs often will not manifest until many years after implementation, the Diabetes Model simulation period enables long term benefits to be assessed beyond traditional government planning horizons. By comparing the results of the base case status quo projection to alternative simulations premised on interventions that either reduce the prevalence of diabetes risk factors or improve diabetes control among those known to have the disease, it is possible to identify the extent to which short run investments can reap long term benefits in both human and economic terms.

This article contains 3 tables.

Tables

Table 1. Socio-Demographic and Lifestyle Related Risk Factors for Type 2 Diabetes.

Risk Factor	Metrics and Threshold Values
Sex
Age^a	Six categories of ten year age groups from 25–34 years up to 75+ years
Income^b:
• Low • Medium • High • Unknown	≤ $399 per week $400 – $799 per week ≥ $800 per week Unknown Income
Waist Circumference:
• Not Obese^c • Obese^d • Very Obese^d	< 102/88 cm (male/female) 102/88 – 108.05/96.925 cm (male/female) ≥ 108.05/96.925 cm (male/female)
Abnormal Cholesterol^e	High-density lipoprotein < 1.03/1.29 mmol/l (male/female)
Hypertension^e	Systolic blood pressure ≥ 140 mmHg and/or Diastolic blood pressure ≥ 90 mmHg
Exercise^a:
• Sufficient • Insufficient • Sedentary	> 150 minutes of physical activity time per week 0 – 150 minutes of physical activity time per week 0 minutes physical activity time per week
Smoking^a:
• Current • Ex-Smoker • Never	Smokes at least daily Smokes less than daily for at least the last three months, but used to smoke daily Smoked less than 100 cigarettes over lifetime

These variable definitions are as specified in the AusDiab survey (refer to Dunstan et al. 2001 and the AusDiab data dictionary available at www.diabetes.com.au/AusDiab2000datadictionary).

The threshold values are based on an aggregation across the seven income ranges reported in the AusDiab survey. The median gross weekly income in Australia in 1999–00 was $535 (ABS 2001).

The 102/88 cm (male/female) measurements are commonly accepted clinical threshold values.

The 108.05/96.925 cm (male/female) values are an empirical threshold that splits the group of people with waist circumference ≥ 102/88 cm (male/female) into equal sizes.

These threshold values were advised by an expert Advisory Group to the project based on clinical experience and with reference to commonly accepted medical guidelines.

Table 2. RACGP Clinical Control Targets, 2008–2009.

Measure	Clinical Target
Glycaemia (HbA1c)	≤ 7%
Body mass index	< 25kg/m2
Total cholesterol	< 4.0 mmol/L
Blood pressure (systolic/diastolic)	≤ 130/80 mm Hg

Table 3. States of Diabetes Control.

State of Control*	Controlled				Not Controlled
State of Control*	Glycaemic	Weight	Lipids	BP	Glycaemic	Weight	Lipids	BP
1 – GWLB	✓	✓	✓	✓
2 – GWLb	✓	✓	✓					✓
3 – GWlB	✓	✓		✓			✓
4 – GWlb	✓	✓					✓	✓
5 – GwLB	✓		✓	✓		✓
6 – GwLb	✓		✓			✓		✓
7 – GwlB	✓			✓		✓	✓
8 – Gwlb	✓					✓	✓	✓
9 – gWLB		✓	✓	✓	✓
10 – gWLb		✓	✓		✓			✓
11 – gWlB		✓		✓	✓		✓
12 – gWlb		✓			✓		✓	✓
13 – gwLB			✓	✓	✓	✓
14 – gwLb			✓		✓	✓		✓
15 – gwlB				✓	✓	✓	✓
16 – gwlb					✓	✓	✓	✓

This refers to the combination of diabetes control across the four different areas of diabetes control. ‘G’ represents glycaemic control, ‘W’ represents weight control, ‘L’ represents cholesterol control and ‘B’ represents blood pressure control. A capital letter denotes that the clinical threshold for control in that area is being met. A lower case letter denotes that the clinical threshold for control in that area is not being met.