Type 2 diabetes is the most common form of diabetes in Australia. Almost 1.2 million (4.6%) people were living with type 2 diabetes in 2021, although this is likely to be an underestimate of the true prevalence.5 In addition, almost one in six adults are affected by impaired glucose tolerance (IGT) or impaired fasting glucose (IFG).8
Clinical suspicion for type 2 diabetes needs to remain high, because type 2 diabetes is often asymptomatic and is increasingly developing in younger people (refer to ‘Early-onset type 2 diabetes’).6 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.8
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,5 and people with certain ethnicities (Aboriginal and Torres Strait Islander people, South Asian, South-east Asian, North African, Latin American, Middle Eastern, Māori or Pacific Islander people [includes individuals of mixed ethnicity]).1
Aboriginal and Torres Strait Islander peoples have almost three times the rate of type 2 diabetes than other Australians, with onset at an earlier age.9 Type 2 diabetes is a direct or indirect cause of 20% of deaths among Aboriginal and Torres Strait Islander people.10 There are many structural barriers to access to and affordability of healthy foods for many Aboriginal and Torres Strait Islander people, and colonisation has disrupted traditional diets and knowledge of food systems.2 (Refer to the National Aboriginal Community Controlled Health Organisation [NACCHO]–Royal Australian College of General Practitioners [RACGP] National guide to preventive healthcare for Aboriginal and Torres Strait Islander people).
Assessing diabetes risk
People should be assessed for diabetes risk every three years from the age of 40 years using the Australian type 2 diabetes risk assessment tool (AUSDRISK; Table 1).3
Aboriginal and Torres Strait Islander people
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 the age of 18 years.2
Refer to the NACCHO-RACGP National guide to preventive healthcare for Aboriginal and Torres Strait Islander people.
An AUSDRISK score of ≥12 is considered ‘high risk’ for developing type 2 diabetes (Table 1). The following people are also considered at high risk, regardless of AUSDRISK score:1,3
- any age with IGT or IFG
- overweight or obesity and age ≥40 years
- overweight or obesity, age 18–40 years and hypertension
- overweight or obesity, age 18–40 years and clinical evidence of insulin resistance (acanthosis nigricans, dyslipidaemia)
- a first-degree relative with type 2 diabetes
- a history of a cardiovascular event (eg acute myocardial infarction, angina, peripheral vascular disease or stroke)
- certain ethnicities (Aboriginal and Torres Strait Islander, South Asian, South-east Asian, North African, Latin American, Middle Eastern, Māori or Pacific Islander people [includes individuals of mixed ethnicity])
- a history of GDM
- PCOS
- taking antipsychotic medication.
It is recommended that all people at high risk are tested every three years for diabetes with either FBG or a non-fasting HbA1c (refer to ‘Diagnosing diabetes in asymptomatic people’).1,3 People with IGT or IFG should be tested annually.3 For recommended management of people at high risk of developing diabetes, refer to ‘Preventing progression to type 2 diabetes’.
For recommendations on screening in pregnancy, refer to ‘Type 2 diabetes, reproductive health and pregnancy’.
Aboriginal and Torres Strait Islander people
Obesity is a major cause of type 2 diabetes; Aboriginal and Torres Strait Islander adults who are obese are sevenfold more likely as those of healthy weight or underweight to have diabetes (17% versus 2.4%, respectively).10 Obesity is a very strong predictor of who may get type 2 diabetes in the future; a study of non-diabetic Aboriginal adults in Central Australia found that those who were overweight or obese were 3.3-fold more likely to develop diabetes than those who were not.2,3
The AusDiab study found that BMI, waist circumference and waist-to-hip ratio all had similar correlations with diabetes and cardiovascular disease (CVD) risk.11 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 have central obesity. For men, a BMI ≥25 kg/m2 was a better predictor than BMI ≥30 kg/m2 or a waist circumference ≥102 cm.12
Table 1. AUSDRISK tool for assessing type 2 diabetes risk13
|
AUSDRISK score
|
Risk of developing type 2 diabetes within five years*
|
≤5
|
1 in 100
|
6–8
|
1 in 50
|
9–11
|
1 in 30
|
12–15
|
1 in 14
|
16–19
|
1 in 17
|
≥20
|
1 in 3
|
*The overall score may overestimate the risk of diabetes in those aged <25 years and underestimate the risk in Aboriginal and Torres Strait Islander people.1
|
IFG and IGT
The definition of diabetes is based on a collection of symptoms and agreed glycaemic measures associated with escalating retinopathy risk. People 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 OGTT (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 people 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 ‘Preventing progression to type 2 diabetes’.