DATA SOURCES AND DEFINITIONS

Data in this article are sourced from the 2001, 2004-05 and 2007-08 National Health Surveys (NHS) and, unless otherwise stated, relates to self-reported consumption of alcohol. The collection of accurate data on quantity of alcohol consumed is complex, particularly where recall is concerned, given the nature and possible circumstances of consumption.

Some under-reporting of consumption, both in terms of persons identifying as having drank alcohol in the reference week, and in the quantities reported, is expected to have occurred. Any under-reporting which may have occurred, however, does not invalidate the survey results as indicators of relative consumption levels (current and over time), or the relative health risks of the consumption levels identified.

Respondents were asked to record all days in the previous week on which they had consumed alcohol, but details of consumption (type, brand and quantity) were only collected for the three most recent days on which they had consumed alcohol. Due to the fact that more people were interviewed early in the week, this methodology may have resulted in the possibility that mid-week drinking occasions could be under-represented in the calculation of level of risk, and weekend drinking occasions could be over-represented.

It should be noted that whereas the 2001 and 2009 NHMRC guidelines assume ongoing consumption at the levels reported, indicators derived from the 2007-08 NHS relate to consumption only during the reference week and take no account of whether or not consumption in that week was more than, less than, or similar to usual consumption levels. While data may not necessarily reflect the usual drinking behaviour of respondents at the individual level, at the population level this is expected to be representative of the total population.

For further information on collection of information on consumption of alcohol, see the National Health Survey: Summary of Results, 2007-08 (cat. no. 4364.0) or Module M of the National Health Survey: Questionnaire, 2007-08.


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 relationships between variables. For example, the age distribution of the population of Australia is changing over time. As levels of alcohol consumption may be related to age, any changes in consumption over time might be due to actual changes in consumption as well as to changes in the age structure of the population. Age standardising removes the effect of age in assessing change over time.