Type 2 diabetes is the most common form of diabetes in Australia. Five per cent of adults have a diagnosis of type 2 diabetes, although this is likely to be an underestimate of the true prevalence.6 Additionally, almost one in six adults are affected by impaired glucose tolerance (IGT) or impaired fasting glucose (IFG).3
Clinical suspicion for type 2 diabetes needs to remain high, as type 2 diabetes is often asymptomatic and is increasingly developing in younger people (refer to the section ‘Early-onset type 2 diabetes’).4 Causes of secondary diabetes, such as diseases of the exocrine pancreas (eg pancreatic cancer, cystic fibrosis, haemochromatosis), metabolic, or drug-induced causes (eg treatment of human immunodeficiency virus [HIV]), should also be considered in the presence of symptoms suggestive of diabetes.3
Type 2 diabetes in specific populations
There is a higher prevalence of type 2 diabetes among Australians from lower socioeconomic backgrounds compared with higher socioeconomic groups,6 and certain ethnic groups are more at risk: people with Pacific Islander, Southern European or Asian backgrounds are more than twice as likely as other Australians to develop diabetes within five years.7
Aboriginal and Torres Strait Islander people are almost four times more likely to have diabetes than non-Indigenous Australians,6 and type 2 diabetes is a direct or indirect cause of 20% of Aboriginal and Torres Strait Islander people deaths.8 Furthermore, the average age of diabetes onset is younger for Aboriginal and Torres Strait Islander people than non-Indigenous Australians,9 and in some populations, Aboriginal children and adolescents have rates of type 2 diabetes that are 6–20 times higher than non-Indigenous youth.10
Assessing diabetes risk
Patients should be assessed for diabetes risk every three years from 40 years of age using the Australian type 2 diabetes risk assessment tool (AUSDRISK; Table 1).1
Aboriginal and Torres Strait Islander point
Given the high background prevalence of type 2 diabetes in Aboriginal and Torres Strait Islander adults, AUSDRISK has limited use as a screening tool in this population.
Aboriginal or Torres Strait Islander people should instead proceed directly to blood testing for diabetes, in conjunction with other opportunistic screening (such as for cardiovascular risk assessment) from 18 years of age.2
An AUSDRISK score of ≥12 or more is considered ‘high risk’ for developing type 2 diabetes (Table 1). The following people are also considered at high risk, regardless of AUDRISK score:1,11
- people aged ≥40 years who are overweight or obese
- people of any age with IGT or IFG
- people with a first-degree relative with diabetes
- all patients with a history of a cardiovascular event (eg acute myocardial infarction, angina, peripheral vascular disease or stroke)
- people of high-risk ethnicity/background (eg Pacific Islands, Indian subcontinent)
- women with a history of GDM
- women with polycystic ovary syndrome (PCOS)
- people taking antipsychotic medication
- Aboriginal and/or Torres Strait Islander people.
It is recommended that all patients at high risk are tested every three years for diabetes with either FBG or HbA1c (refer to ‘Diagnosing diabetes in asymptomatic patients’).1,11 People with IGT or IFG should be tested annually.1 For recommended management of people at high risk of developing diabetes, refer to the section ‘Preventing progression to type 2 diabetes’.
Refer to the section ‘Type 2 diabetes, reproductive health and pregnancy’ for recommendations on screening in pregnancy.
Aboriginal and Torres Strait Islander point
Aboriginal and Torres Strait Islander adults who are obese are seven times as likely as those of normal weight or underweight to have diabetes (17% compared with 2.4%).2
The AusDiab study found that body mass index (BMI), waist circumference and waist-to-hip ratio all had similar correlations with diabetes and cardiovascular disease (CVD) risk.12 However, a later study of diabetes risk in an Aboriginal community found that in women, central obesity (defined as waist circumference ≥88 cm) or BMI ≥25 kg/m2 were better predictors of type 2 diabetes and CVD risk; many women with ‘normal’ BMIs were found to be centrally obese. For men, a BMI ≥25 kg/m2 was a better predictor than BMI ≥30 or waist circumference ≥102 cm.13
AUSDRISK tool for assessing type 2 diabetes risk7
Impaired fasting glucose and impaired glucose tolerance
The definition of diabetes is based on a collection of symptoms and agreed glycaemic measures associated with escalating retinopathy risk. Patients with elevated glucose not high enough to be diagnosed with type 2 diabetes might have either IFG or IGT, also known as ‘dysglycaemic states’ or ‘intermediate hyperglycaemia’. IFG is identified by a FBG test, and IGT can be identified by a two-hour oral glucose tolerance test (OGTT) – refer to Figure 1.14
These states are not considered benign, and they reflect a risk of developing diabetes in the future; however, IFG and IGT have been shown to regress over three years in 18% of cases, if patients follow standard (ie non-intensive) lifestyle recommendations.15
As CVD risk is distributed across a continuum of post-challenge glucose levels, any degree of post-challenge hyperglycaemia may be associated with the development of premature CVD.16
Refer also to the section ‘Preventing progression to type 2 diabetes’.