Australian Aboriginal and Torres Strait Islander Health Survey: Biomedical Results methodology

Refers to people who identified themselves, or were identified by another household member, as being of Aboriginal, Torres Strait Islander, or Aboriginal and Torres Strait Islander origin.

Age standardisation is a way of allowing comparisons between two or more populations with different age structures, in order to remove age as a factor when examining relationships between variables. For example, the Aboriginal and Torres Strait Islander population has a larger proportion of young people and a smaller proportion of older people than the non-Indigenous population. For this reason, where appropriate, estimates for Aboriginal and Torres Strait Islander people and non-Indigenous people have both been age standardised to reflect the age structure of the same population — the total estimated resident population of Australia as at 30 June 2001. The age standardised rates are the rates that would have prevailed if both populations had this same age structure.

The ratio of albumin (a protein) to creatinine (a waste product) in the urine can determine how well the kidneys are functioning. An elevated ACR result may indicate kidney disease or a reduction in kidney function. In this survey, abnormal ACR - also known as albuminuria - is defined as 2.5 mg/mmol or greater for males, and 3.5 mg/mmol or greater for females.

Albuminuria is defined as the presence of albumin, a type of protein, in the urine. In this survey, the presence of albuminuria was defined as an ACR reading of greater than or equal to 2.5 mg/mmol for males and greater than or equal to 3.5 mg/mmol for females.

Also see Albumin creatinine ratio (ACR), Macroalbuminuria, Microalbuminuria and Normoalbuminuria.

ALT is an enzyme found mainly in the liver. When the liver is damaged or diseased, ALT leaks into the bloodstream. In this survey, abnormal ALT is defined as greater than 40 U/L for males and greater than 30 U/L for females.

Anaemia describes a decrease in either the number of red blood cells in the body or the quantity of haemoglobin within red blood cells.

Also see haemoglobin.

In this survey, a person was considered to be at high risk of diabetes if they did not currently have diabetes, but had an impaired fasting plasma glucose result, that is, a fasting plasma glucose level ranging from 6.1 mmol/L to less than 7.0 mmol/L. The equivalent cut-off for the glycated haemoglobin (HbA1c) test was a value of 6.0% to less than 6.5%.

Also see Diabetes, Known diabetes and Newly diagnosed diabetes.

See High blood pressure.

Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, normal weight, overweight and obesity. It is calculated from height and weight information, using the formula weight (kg) divided by the square of height (m). To produce a measure of the prevalence of underweight, normal weight, overweight or obesity in adults, BMI values are grouped according to the table below which allows categories to be reported against both the World Health Organization (WHO) and National Health and Medical Research Council (NHMRC) guidelines.

CRP is used for ferritin interpretations and measures general levels of inflammation in the body. High levels may mask iron deficiency and therefore people with CRP levels above 10mg/L were excluded from the ferritin results.

Also see Iron and Ferritin.

Cholesterol is a type of fat that circulates in the blood. It is essential for many metabolic processes, including the production of hormones and in building cells. There are two main types of cholesterol: high density lipoprotein (HDL) and low density lipoprotein (LDL).

Also see Total cholesterol, HDL cholesterol and LDL cholesterol.

Chronic kidney disease stages were derived using a combination of participants' estimated glomerular filtration rate (eGFR) results with their albumin creatinine ratio (ACR) results. The different stages were defined as follows:

• No indicators of chronic kidney disease - eGFR greater than or equal to 60 mL/min/1.73 m² and no presence of albuminuria
• Stage1 - eGFR greater than or equal to 90 mL/min/1.73 m² & albuminuria
• Stage 2 - eGFR 60 to 89 mL/min/1.73 m² & albuminuria
• Stage 3a - eGFR 45–59 mL/min/1.73 m²
• Stage 3b - eGFR 30–44 mL/min/1.73 m²
• Stage 4–5 - eGFR less than 30 mL/min/1.73 m².

Cotinine is produced in the process of breaking down, or metabolising, nicotine. Elevated levels of cotinine in the blood can be used to determine exposure to tobacco smoke. However, cotinine levels only remain elevated for around 20 hours after exposure to tobacco smoke, therefore it can only provide a measure of short-term exposure. In this survey, cotinine levels of 140 nmol/L or greater indicate exposure to tobacco smoke.

A current daily smoker is a respondent who reported at the time of interview that they regularly smoked one or more cigarettes, cigars or pipes per day. Also see Smoker status.

Diabetes is a chronic condition where insulin, a hormone that controls blood glucose levels, is no longer produced or is not produced in sufficient amounts by the body. In this survey, diabetes prevalence was derived using a combination of blood test results and self-reported information on diabetes diagnosis and medication use.

Also see Known diabetes, Newly diagnosed diabetes and At high risk of diabetes.

Refers to a number of different lipid disorders (that is, conditions where there are too many fats in the blood). In this survey, a person was considered to have dyslipidaemia if they had one or more of the following:

• Taking cholesterol-lowering medication
• Total cholesterol greater than or equal to 5.5 mmol/L
• HDL cholesterol less than 1.0 mmol/L for men and less than 1.3 mmol/L for women
• LDL cholesterol greater than or equal to 3.5 mmol/L
• Triglycerides greater than or equal to 2.0 mmol/L.

eGFR measures the rate at which the kidneys filter wastes from the blood. In this survey, abnormal kidney function using eGFR is defined as a reading of less than 60 mL/min/1.73m².

A blood test that measures the amount of glucose (a sugar) in the blood. In this survey, fasting plasma glucose levels of 7.0 mmol/L or greater indicates diabetes. A fasting plasma glucose level from 6.1 mmol/L to less than 7.0 mmol/L is known as impaired fasting plasma glucose and indicates that a person is at high risk of diabetes.

Ferritin measures the amount of iron stores in the body. Low ferritin in the blood reflects depleted iron stores. Levels of ferritin can be affected by infection or inflammation, therefore people with inflammation (defined as a C-reactive protein level of >10mg/L) were excluded from the NATSIHMS ferritin results.

Also see C-reactive protein, Iron and Serum transferrin receptor.

Folate is a B group vitamin that is essential for healthy growth and development. Folate is found naturally in food, such as green leafy vegetables, fruits and grains, while folic acid is the synthetic form of folate added to food or used in dietary supplements. Folate can help prevent neural tube defects in babies, including spina bifida, if it is taken before conception and early in pregnancy. Folate status can be assessed by measuring serum folate, which provides information on recent intake.

Also see Serum folate.

GGT is an enzyme that is found in high concentrations in the liver, and in lesser concentrations in the kidneys, bile duct, pancreas, gallbladder, spleen, heart, and brain. When these tissues are damaged by disease or inflammation, GGT leaks from the tissue into the bloodstream. Abnormal GGT is defined as greater than 50 U/L for males and greater than 35 U/L for females.

Haemoglobin is an iron-containing protein and is found in the red blood cells and helps transport oxygen from the lungs to the rest of the body. Low haemoglobin levels in the blood may indicate anaemia. In this survey, the risk of anaemia is defined using haemoglobin levels. For non-pregnant women, haemoglobin levels less than 120 g/L are defined as at risk of anaemia. For pregnant women, haemoglobin levels less than 110 g/L are defined as at risk of anaemia. For males, haemoglobin levels less than 130 g/L are defined as at risk of anaemia.

See also Anaemia.

Glycated haemoglobin, commonly known as HbA1c, is a blood test that measures what the person's average blood glucose level has been in the previous three months. Results from the HbA1c test can be expressed either as a percentage (%) or as a measurement in mmol/mol. In this survey, normal HbA1c is defined as less than 6.0%; at high risk of diabetes is defined as 6.0% to less than 6.5% and levels greater than or equal to 6.5% indicate diabetes.

High density lipoprotein (HDL) cholesterol is the measure of "good" cholesterol. HDL picks up excess cholesterol in the blood and takes it to the liver where it is broken down. High levels of HDL cholesterol reduce the risk of heart disease, while low levels increase the risk. In this survey, abnormal HDL cholesterol is defined as less than 1.0 mmol/L for males, and as less than 1.3 mmol/L for females.

A measured blood pressure reading of 140/90 mm Hg (millimetres of mercury) or higher. Data on high blood pressure in this publication refer to measured blood pressure only, and do not take into account whether people who might otherwise have high blood pressure are managing their condition through the use of blood pressure medications.

A fasting plasma glucose level ranging from 6.1 mmol/L to less than 7.0 mmol/L. Also see At high risk of diabetes.

Iodine is an important nutrient for the production of thyroid hormones. It is essential for brain development, particularly in young children and infants. Deficiency in iodine can cause goitres, hypothyroidism, fetal brain damage and developmental delays. The major dietary sources of iodine include seafood, especially seaweed, and baked bread and dairy milk.

The WHO considers a population iodine deficient if the median urinary iodine concentration is less than 100 μg/L. They also recommended that no more than 20% of the population have iodine concentrations below 50 μg/L.

Iron is an essential mineral for transporting oxygen around the body. Iron deficiency can lead to fatigue, tiredness and decreased immunity. Measures of iron intake in the NATSIHMS include Ferritin and Serum transferrin receptor.

Also see Ferritin and Serum transferrin receptor.

See Chronic kidney disease stages.

In this survey, a person was considered to have known diabetes if:

• they had ever been told by a doctor or nurse that they have diabetes and they were taking diabetes medication (either insulin or tablets); OR
• they had ever been told by a doctor or nurse that they have diabetes and their blood test result for fasting plasma glucose was greater than or equal to the cut off point for diabetes (that is, greater than or equal to 7.0 mmol/L).

People who had been told by a doctor or nurse that they have diabetes, but who were not taking medication for diabetes and did not have a fasting plasma glucose level of 7.0 mmol/L or greater, were classified as not having diabetes.

People with known diabetes were further classified as having Type I, Type II or Type unknown, based on the type of diabetes that a doctor or nurse told them they had. Women with gestational diabetes were excluded.

The corresponding diabetes cut-off for HbA1c is a value of 6.5% or greater.

Low density lipoprotein (LDL) cholesterol is the measure of "bad" cholesterol in the blood. Over time, LDL cholesterol can build up in the blood vessels and arteries, blocking the passage of blood flow. In this survey, abnormal LDL cholesterol is defined as 3.5 mmol/L or greater.

Also see Total cholesterol and HDL cholesterol.

An increased amount of albumin, a protein, in the urine. Macroalbuminuria is defined as an albumin creatinine ratio (ACR) of more than 25 mg/mmol for males, or more than 35 mg/mmol for females. Also see Albumin creatinine ratio (ACR).

Describes the distance from the precision of the estimate at a given confidence level, and is specified at a given level of confidence (95% in this publication). In this publication, Margin of error has only been provided for proportions and rate ratios. For more information see the Technical Note.

A slightly increased amount of albumin, a protein, in the urine. Microalbuminuria is defined as an albumin creatinine ratio (ACR) of 2.5 to 25 mg/mmol for males, or 3.5 to 35 mg/mmol for females. Also see Albumin creatinine ratio (ACR).

In this survey, a person was considered to have newly diagnosed diabetes if they reported no prior diagnosis of diabetes but had a fasting plasma glucose value of 7.0 mmol/L or greater. The equivalent cut-off for the HbA1c test is a value of 6.5% or greater.

Also see Known diabetes and At high risk of diabetes.

Calculated by subtracting the level of HDL cholesterol from the level of total cholesterol. Non-HDL cholesterol levels are monitored as part of diabetes management as a tool to assess cardiovascular risk.

Normal levels of protein in the urine. Normoalbuminuria is defined as an albumin creatinine ratio (ACR) of less than 2.5 mg/mmol for males, or less than 3.5 mg/mmol for females. See also Albumin creatinine ratio (ACR).

See Body Mass Index (BMI).

See Body Mass Index (BMI).

See Body Mass Index (BMI).

Aboriginal and Torres Strait Islander to non-Indigenous rate ratios are calculated by dividing the proportion of Aboriginal and Torres Strait Islander people with a particular characteristic by the proportion of non-Indigenous people with the same characteristic. If the characteristic of interest is highly correlated with age (e.g. diabetes), age standardised proportions are used to calculate Aboriginal and Torres Strait Islander to non-Indigenous rate ratios. A rate ratio of 1.0 indicates that the prevalence of the characteristic is the same in the Aboriginal and Torres Strait Islander and non-Indigenous populations. Rate ratios greater than 1.0 indicate higher prevalence in the Aboriginal and Torres Strait Islander population and rate ratios less than 1.0 indicate higher prevalence in the non-Indigenous population. Rate ratios produced for this publication were based on age standardised proportions to two decimal places.

The standard error expressed as a percentage of the estimate. For more information see the Technical Note.

The Remoteness Structure for the Australian Statistical Geography Standard (ASGS) 2011, has five categories based on an aggregation of geographical areas which share common characteristics of remoteness, determined in the context of Australia as a whole. These categories are:

• Major cities of Australia
• Inner regional Australia
• Outer regional Australia
• Remote Australia
• Very remote Australia.

The five categories are generally aggregated in some way for use in output.

The 2011 Remoteness Structure has been built using the same principles as the 2006 Remoteness Structure. The primary difference is that it was built from ASGS Statistical Area Level 1 (SA1) regions rather than from 2006 Census Collection Districts (CCD).

A measure the level of folate in the body. It is sensitive to folate intake and can fluctuate due to short-term changes in diet.

Also see Folate.

An indicator of iron levels in the body. It is not as affected by infection or inflammation as other measures, such as ferritin.

The extent to which a respondent was smoking at the time of interview, and refers to regular smoking of tobacco, including manufactured (packet) cigarettes, roll-your-own cigarettes, cigars and pipes, but excludes chewing tobacco and smoking of non-tobacco products. Categorised as:

• Current daily smoker - a respondent who reported at the time of interview that they regularly smoked one or more cigarettes, cigars or pipes per day;
• Current smoker - Other - a respondent who reported at the time of interview that they smoked cigarettes, cigars or pipes, less frequently than daily;
• Ex-smoker - a respondent who reported that they did not currently smoke, but had regularly smoked daily, or had smoked at least 100 cigarettes, or smoked pipes, cigars, etc at least 20 times in their lifetime; and
• Never smoked - a respondent who reported they had never regularly smoked daily, and had smoked less than 100 cigarettes in their lifetime and had smoked pipes, cigars, etc less than 20 times.

Total cholesterol is a measure of all the different types of fats in the blood. In this survey, abnormal total cholesterol is defined as 5.5 mmol/L or greater.

Also see Cholesterol, HDL cholesterol, and LDL cholesterol.

Triglycerides are a fatty substance in the blood. They work as a type of fuel, circulating in the bloodstream to be used as energy by the cells. In this survey, abnormal triglycerides are defined as 2.0 mmol/L or greater.

See Body Mass Index (BMI).

Vitamin B12 is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. Vitamin B12 is a nutrient that helps keep the body's nerve and blood cells healthy and helps make DNA. If left untreated, Vitamin B12 deficiency, also known as B12 deficiency, can lead to anemia, as well as nerve and brain damage.

Vitamin D is essential for the body to absorb calcium effectively. The main source of Vitamin D is exposure to sunlight, although small amounts can be obtained through some foods, such as eggs, fatty fish and fortified margarine and milk. The main consequence of severe Vitamin D deficiency is rickets in children and osteopenia (fragile bones) in older people. In the NATSIHMS, the levels recommended in a recent Australian position statement on Vitamin D have been applied to determine Vitamin D deficiency. These are:

• Mild deficiency: 30 – 49 nmol/L
• Moderate deficiency: 13* – 29 nmol/L
• Severe deficiency: <13* nmol/L
• Total deficiency: <50 nmol/L
• Adequate levels: ≥50 nmol/L#.

* Note that the cut-off recommended in the position statement is <12.5 nmol/L, but the NATSIHMS is unable to output against this cut-off as the Vitamin D data is only available in whole numbers.
# Note that the position statement states that levels may need to be 10 to 20 nmol/L higher at the end of summer, to allow for seasonal decrease.

Waist circumference is associated with an increased risk of metabolic complications associated with obesity. The WHO and National Health and Medical Research Council (NHMRC) approved the following guidelines for Caucasian men and women: