Epidemiology is the study of the patterns, causes and effects of health and disease conditions in populations. Data is obtained from various sources such as hospitals, GPs, health care practitioners, emergency services, surveys and Census information.

It involves the analysis of data related to health and disease in a population often reported as percentages or rates per 1,000 or 100,000 people. An example could be studying the number of smokers in a particular population and its health risks to develop effective anti-smoking programs.

According to AIHW (2024) epidemiological data needs to be accurate and comparable to allow authorities to identify health trends, assess the effectiveness of current programs, allocate resources and develop targeted strategies for improving health outcomes.

Data obtained through epidemiological analysis can be used by various individuals and groups in the community such as those working in research, health, health promotion, injury and disease prevention, government and education to identify priority health issues, possible causes or disease or illness and then to make decisions about Australia’s health.

Mortality refers to the number of deaths in a population. In 2022, CVD was the underlying cause of 45,000 deaths (24% of all deaths), a rate of 173 per 100,000 population. CVD was the second leading cause of death group, behind cancers (27% of all deaths) (AIHW, 2024).

The image below from AIHW displays data about the leading causes of death among males and females in 2022.
This graph helps explain mortality data with coronary heart disease as the leading cause of death for males (11,303) and dementia including Alzheimer's disease as the leading cause of death for females (10,976) (AIHW, 2024). 

Infant mortality is the death of an infant before their first birthday. The infant mortality rate in Australia was 3.2 deaths per 1,000 live births in 2023 (AIHW, 2024). In some remote Indigenous communities in Australia, the infant mortality rate can be as high as 20 per 1,000 live births. According to Red Nose (2024) since 2010, there has been a 22% reduction in the overall infant mortality rate for Indigenous Australian infants.

The AIHW (2024) image below displays infant mortality rates in Australia from 1911 to 2023. The data in this graph obtained from ABS indicates the significant reduction in infant mortality rates over the last 100 years, in particular the rapid decline from the early 1900s to the mid 1940s due to improvements in sanitation, education, vaccination and antibiotics.   

Morbidity refers to illness or disease in a population. An example of a morbidity measure would be back problems in Australia.

The graph below displays the 'Most common long-term health conditions by sex and age, 2022'  in Australia (AIHW, 2023). Anxiety was the highest long-term condition for both males and females accounting for almost 19%, highlighting the significant burden of this condition (AIHW, 2023). The graph also indicates that back problems were the most common long-term illness for males accounting for 2.1 million (16%) and anxiety was the most common for females accounting for 2.9 million (22.5%) (AIHW, 2023).

The incidence of disease is the number of new cases of a disease that occur in a population over a given period of time. For example, cancer incidence rates continue to rise as Australia grows and ages; it sits at 503.1 new cases per 100,000 people, 164,694 new cases diagnosed in 2023. (AIHW, 2024).

The graph 'Age-standardised cancer incidence and mortality rates, persons, 200-2004' (AIHW, 2024) sourced from the AIHW Australian Cancer Database 2020 and National Mortality Database demonstrates the correlation between incidence and mortality rates. Increasing cancer survival rates increase the gap between incidence and mortality rates due to a number of factors including education, prevention, early intervention and treatment.

The prevalence of disease is the proportion of a population that has a particular disease at a given point in time. For example, the prevalence of asthma in Australia was 11% in 2022, affecting around 2.8 million people. Another example is between 2020 -2022, around 46% of Australian women aged 16-24 had a 12-month mental health illness (AIHW, 2024).

Below the graph 'Disability prevalence by age and sex, 2022' sourced from ABS (2022) shows the percentage of males and females in Australia with a disability by age and sex. This graph displays the increase in prevalence of disability as Australian's get older which correlates with Australia's ageing population. 

Data obtained through epidemiological analysis can be used by various individuals and groups in the community such as those working in research, health, health promotion, injury and disease prevention, government and education to identify priority health issues, possible causes or disease or illness and then to make decisions about Australia’s health.

Epidemiology uses data on death rates, birth rates, illnesses, injuries, treatments provided, work days lost, hospital usage and money spent by both consumers and the government. Such data can be used to develop preventative measures, create early intervention approaches and make informed decisions about the health and wellbeing of individuals.

Although measures are put in place to increase accuracy of data, epidemiology has many limitations. At the basic level, statistics and data like epidemiology can be manipulated by the interpreters and are very open to bias. They also tend to focus on negative measurable aspects of health and not the positive, less measurable aspects such as wellbeing and quality of life. They also do not account for the determinants of health: individual, sociocultural, socioeconomic and environmental factors. Epidemiology provides little if any data on the impact of disease and illness.

For example, graphs from various organisations could show the estimated incidence of illness or disease in Australia and because of the nature of using these patterns to predict future data, it may potentially be open to bias or misinterpretation. 

Therefore, it's essential to interpret epidemiology with some caution and use other research, such as randomised controlled trials, to establish causality.

Despite these limitations, epidemiology is a critical tool for informing public health policy and promotions in Australia. For example, epidemiological studies have been used to inform policies to reduce smoking and its related health conditions - lung cancer and cardiovascular disease. These policies include taxation, regulation of advertising and plain packaging of tobacco products. 

Overall, epidemiology is critical in understanding the health status of Australians and informing health-related interventions. While there are some limitations to the data, it remains an essential tool for tracking health trends, identifying risk factors and guiding public health interventions.