DATA SOURCES AND DEFINITIONS

Data was sourced from the 2007-08 and 2001 National Health Surveys (NHS) and relates to self-reported physical activity for fitness, recreation and sport, walking for transport and physical activity undertaken as part of an individual's occupation.


EXERCISE

The 2007-08 National Health Survey (NHS) collected data about the exercise people had undertaken for fitness, recreation or sport in the week and two weeks prior to interview. From this, people were grouped into four exercise levels (sedentary, low, moderate, or high), based on a scored derived from the frequency, duration and intensity (i.e. walking, moderate exercise and vigorous exercise) of their physical activity.

A high level of exercise included one or more hours of vigorous exercise during the one week period, while a moderate level included less than one hour. A low or sedentary level of exercise included either no exercise or little exercise during the week or two weeks prior to interview. Moderate exercise was defined as exercise undertaken for fitness, recreation or sport that caused a moderate increase in the heart rate or breathing of the respondent. Vigorous exercise was defined as exercise undertaken for fitness, recreation or sport that caused a large increase in the respondent’s heart rate or breathing.

Data from questions on walking for transport, level of activity at work and time spent sitting did not contribute to the calculation of exercise level.

Unless otherwise stated, the levels of physical activity referred to in this article are based on activity undertaken for sport, recreation or fitness in the last week.

For more information about how these exercise levels were derived see the National Health Survey Users' Guide, September 2009 (cat. no. 4363.0.55.001).


BODY MASS INDEX (BMI)

Overweight and obesity are calculated using Body Mass Index (BMI), a simple index that is commonly used in classifying people as overweight and obese. It is defined as the weight in kilograms divided by the square of the height in metres (kg/m²). 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 Organisation (WHO) and, in Australia, the National Health and Medical Research Council guidelines.

Body Mass Index, Adult

Underweight: Less than 18.5
Normal range: 18.5 to less than 25.0
Overweight: 25.0 to less than 30.0
Obese: 30.0 and greater

EQUIVALISED HOUSEHOLD INCOME

Equivalised household income is the total income at the household level adjusted using an equivalence scale to enable analysis of the relative incomes of households of different size and composition. This can be viewed as an indicator of the economic resources available to a standardised household.


AGE STANDARDISATION

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 correlations between other variables. For example, the age distribution of people with diabetes is heavily skewed towards the higher age groups (that is, older people are more likely to have diabetes than younger people). When looking at the labour force status of people with and without diabetes, it can be seen that more people with diabetes are not in the labour force, however, this could be due to the fact that there are more older people with diabetes and less older people in the work force. Age standardising removes age from the picture so it can be seen whether there is a correlation between diabetes and labour force status independent of age.

In this article, the Australian 2001 estimated resident population is used as the reference population.