Significant advances in HIV antiretroviral therapy (ART) has substantially decreased Acquired Immune Deficiency Syndrome (AIDS) associated mortality and morbidity , . The increase in survival has meant that a growing proportion of people living with HIV (PLHIV) are elderly . In Australia, the HIV epidemic remains highly concentrated among men who have sex with men (MSM), a well-educated and informed population with high access to publicly funded and freely available combination ART.
The nature of medical treatment required by PLHIV will change as they age. There is an increased risk of many health conditions associated with increased greater age; these include stroke and cardiovascular disease, cancers, frailty, kidney disease and liver disease .
However, there is strong evidence that HIV infection further increases the risk of many of these conditions –. The increasing numbers of PLHIV, and ageing nature of the population, means that there will be a greater number of people requiring complex clinical care including management of these chronic diseases along with HIV treatments with complicated antiretroviral regimens. The changing demographics of PLHIV require health systems to accommodate for the increased numbers of people with these complex healthcare requirements. Specialised and experienced clinicians are required to care for the needs of these patients but they are in relatively scarce supply . Therefore, there is a need to plan for the health requirements of this important population, not only in magnitude but also according to demographic profiles, including specific geographical settings. By understanding the age structure of the population of PLHIV, necessary health care provisions can be made for those living with HIV ahead of time. Knowledge of the geographical distribution of people living with HIV can help us determine if the provisions made for PLHIV are appropriate for the area. Knowledge of both location and age of individuals allows for precise allocation of resources to maximise effective treatment and prevention on limited budgets.
HIV surveillance in Australia is based on routine case reporting of diagnoses of HIV being notified to local health authorities and then centrally collated at a national level. However, national registries do not monitor linkage into clinical care or other post HIV diagnosis events. Therefore, obtaining estimates of the profiles of populations of all PLHIV require mechanisms outside normal surveillance activities, such as the use of mathematical modelling.
While it can be helpful to discuss an epidemic in terms of averages and the largest affected population group, the finer elements of an epidemic need to be understood to fully grasp the nature of the epidemic and the most effective responses to it. In this study, we aim to project a detailed profile of the demographic characteristics of the population of PLHIV in Australia, based on Australia's National HIV Registry, migration patterns, geographical region-specific survival rates, and HIV/AIDS mortality ratios. These projections are carried out with the development of a detailed agent-based mathematical model. This approach has been applied in other settings, such as predictions of the HIV epidemic in Zimbabwe . A previous model has produced estimations of the age of PLHIV in Australia who identify as MSM . The current study advances previous work by utilising more sources of information, and incorporating greater demographic detail (such as geographical location and migration) to project several important characteristics about the future population of PLHIV in Australia.
Advances in HIV antiretroviral therapy (ART) has reduced mortality in people living with HIV (PLHIV), resulting in an ageing population of PLHIV. Knowledge of demographic details such as age, geographical location and sex, will aid in the planning of training and resource allocation to effectively care for the future complex health needs of PLHIV.
An agent-based, stochastic, geographical model was developed to determine the current and future demographic of PLHIV in Australia. Data and parameters were sourced from Australia's National HIV Registry and peer reviewed literature. Processes that were simulated include progression to AIDS, mortality and internal migration.
The model estimates the mean age of PLHIV in Australia is increasing at a rate of 0.49 years each year. The expected proportion of PLHIV in over 55 years is estimated to increase from 25.3% in 2010 to 44.2% in 2020. Median age is lower in inner-city areas of the capital cities than in rural areas. The areas with the highest prevalence of HIV will continue to be capital cities; however, other areas will have greater percentage growth from 2010 to 2020.
The age of the population of people living with HIV is expected to increase considerably in the future. As the population of PLHIV ages, specialist clinical training and resource provision in the aged care sector will also need to be addressed.