Chronic conditions among ex-serving ADF members

The estimates of chronic conditions are subject to limitations due to the data sources and methodology used to identify chronic conditions. Broadly, these limitations may mean that estimates produced from the VHD underestimate the prevalence of chronic conditions. 

Some of these limitations include:

• Prevalence estimates do not include chronic conditions that have been diagnosed in private hospitals (including for services funded by DVA) or by a GP or other medical specialist. As a result, some conditions will be underestimated, for example, skin cancer is more likely to be treated in a primary care setting.
• Measurement of a condition is based on information within each year, that is a person will only be identified as living with a condition if they have received a hospital diagnosis or been dispensed medication for a condition within that year only. This will not count any people who have a chronic condition despite not having been diagnosed or dispensed medication in that year.
• Measurement of a condition did not take into account the duration of the condition.
• Persons needed to be alive on the last day of each year to be included in the analysis. Given that many people who die have a chronic condition as an underlying or associated cause of death, the analysis is likely to underestimate persons with chronic conditions.
• The simplicity of the dispensed medication methodology when applied across the range of conditions will vary in accuracy between conditions.
• Hospital services will generally only record chronic conditions listed as a principal or additional diagnosis if it affected their care (with some exceptions such as diabetes). This means that hospitalisations of people with no or minor symptoms of a chronic condition are less likely to affect care and thus not be identified as having that condition.
• Measurement of chronic conditions through medication dispensing did not include over-the-counter medication due to data limitations.
• Measurement of chronic conditions did not use Medicare Benefits Schedule (MBS) data. This is due to data limitations on the reasons for which the person sought care.
• There could be other reasons that people might receive medications which would cause an overestimate and there could be other types of medication that are used to treat conditions but may indicate the existence of a condition but with lower confidence which would cause an underestimate of prevalence.
• Medication usage may vary over time due to changes in practitioner behaviour which could impact analysis of trends.
• Persons living in or receiving treatment in Western Australia or Northern Territory were excluded from the estimates derived from VHD.
• No Defence funded or non-Government funded (such as by private insurance or the individual) health services were analysed which means that where these services could identify prevalence of chronic conditions, the AIHW will underestimate prevalence of chronic conditions.
• Ex-serving members may have greater access to health services which could mean there is a bias present when making prevalence comparisons with the Australian population based on health service use.
• The Australian estimated resident population as of 30 June 2001 was chosen as the standard population for consistency with other relevant AIHW reports and limitations in available datasets in the secure environment. The demographic shifts since 2001 should not be substantial enough to affect most results especially since age categories are roughly 10 years long. However, chronic conditions sensitive to demographic changes such as dementia may be biased in age-standardised prevalence. The standard population also has a different age structure when compared to the ex-serving ADF population which may impact the effectiveness and reliability of comparing the age-standardised prevalence of these two populations. Thus, care should be taken when interpreting results.
• Analysis presented by separation reason only contains ex-serving ADF members who separated from 1 January 2003 onwards because of changes to the way the reason for separating the ADF was recorded in 2002.

There are also limitations with the Census approach of estimating prevalence:

• The question used to identify prevalence of a condition is simple and may not be accurately interpreted by respondents which leads it to underestimate prevalence (Comparing ABS long-term health conditions data sources)
• Respondents may not wish to identify as living with a condition or identify as an ex-serving ADF member
• The Census collects information on whether a person had ever had a condition, regardless of whether it requires treatment or not. This information may be less useful than understanding whether a person currently is receiving treatment for the condition.
• The Census is only collected every 5 years so cannot be used for timely monitoring of prevalence of chronic conditions.
• Health condition information has only been collected in 2021 previously, which prevents any trend analysis, and while it will also be collected in 2026, it may not be included in every future Census.