additional diagnosis: A condition or complaint either coexisting with the principal diagnosis, or arising during the episode of admitted patient care, episode of residential care, or attendance at a health-care establishment.

admitted patient: A patient who undergoes a hospital’s admission process to receive treatment and/or care. This treatment and/or care is provided over a period of time, and can occur in hospital and/or in the person’s home (for hospital-in-the-home patients).

age weighting: A method sometimes used to adjust the relative ‘value’ of years lived at different ages – for example, to value a year lived by a young adult more highly than a year lived at older ages. If applied, age weighting results in some age groups having an increased influence on the estimates of disease burden relative to other age groups.

age-standardisation: A set of techniques used to remove, as far as possible, the effects of differences in age when comparing 2 or more populations.

age-standardised rate: Rate that takes into account the age structure of the population.

attributable burden: The disease burden attributed to a particular risk factor. It is the reduction in fatal and non-fatal burden that would have occurred if exposure to the risk factor had been avoided or reduced to its theoretical minimum risk exposure distribution.

burden of disease (and injury): The quantified impact of a disease or injury on a population using the disability-adjusted life year (DALY) measure.

chronic: Persistent and long-lasting.

comorbidity: A health problem/disease that exists at the same times as (an)other health problem(s).

conceptual disease model: A representation of clinical conditions designed to summarise what is known about the disease epidemiology, the nature of the disease (that is, whether it is chronic, acute, episodic or progressive), and its treatment.

condition (health condition): A broad term that can be applied to any health problem, including symptoms, diseases and certain risk factors, such as high blood cholesterol and obesity. Often used synonymously with disorder or problem.

counterfactual: An alternative risk factor exposure distribution chosen for comparison with the observed distribution, to estimate the alterable contribution of that risk factor to the burden of disease. The most commonly used counterfactual in burden of disease studies is the theoretical minimum risk exposure distribution.

disability: In burden of disease analysis, any departure from an ideal health state.

disability-adjusted life years (DALY): A year of healthy life lost, either through premature death or living with disability due to illness or injury.

disability weight: A factor that reflects the severity of health loss from a particular health state on a scale from 0 (perfect health) to 1 (equivalent to death).

disease: A broad term that can be applied to any health problem, including symptoms, diseases, injuries and certain risk factors, such as high blood cholesterol and obesity. Often used synonymously with condition, disorder or problem.

effect modification: A change in the observed magnitude or direction of an association between a risk exposure and an outcome when a third variable (such as age or sex) is included in the analysis.

effect size: A statistical measure of the strength of the relationship between 2 variables (in this context, between a risk exposure and a disease outcome), expressed, for example, as a relative risk or odds ratio.

envelope: The total prevalence of a condition present in the population that is used to constrain the combined prevalence of sequelae common to a number of diseases.

excess burden: The reduction that would occur in overall disease burden if all groups had the same rate of burden as the least burdened group.

external cause: The environmental event, circumstance or condition that causes injury, poisoning and other adverse effect.

fatal burden: The burden from dying prematurely as measured by years of life lost. Often used synonymously with years of life lost, and also referred to as ‘life lost’.

health state: Reflects a combination of signs and symptoms that result health loss, and are not necessarily unique to 1 particular disease. A health state might also be a severity level of a sequela (typically mild, moderate and severe levels are distinguished). For example, the health state ‘mild heart failure’ is used as a sequela of coronary heart disease, hypertensive heart disease, congenital heart disease and several other conditions. Each health state is associated with a disability weight.

hospitalisation: An episode of hospital care that starts with the formal admission process and ends with the formal separation process (synonymous with separation).

incidence: Refers to the occurrence of a disease or event. The incidence rate is the number of new cases occurring during a specified time period.

International Classification of Diseases (ICD): The World Health Organization’s internationally accepted classification of diseases and related health conditions. The 10th revision, Australian modification (ICD-10-AM) is currently in use in Australian hospitals for admitted patients.

linked disease: A disease or injury for which there is evidence that its likelihood is increased by the risk factor in question.

morbidity: Ill health in an individual, and levels of ill health in a population or group.

mortality: Death.

non-admitted patient: A patient who does not undergo a hospital’s formal admission process. There are 3 categories of non-admitted patient: emergency department patient, outpatient, and other non-admitted patient (treated by hospital employees off the hospital site, including community/outreach services). 

non-fatal burden: The burden from living with ill health as measured by years lived with disability. Often used synonymously with years lived with disability, and also referred to as ‘health loss’.

population attributable fraction (PAF): For a particular risk factor and causally linked disease or injury, the percentage reduction in burden for a population that would occur if exposure to the risk factor was avoided or reduced to its theoretical minimum.

premature death: Deaths that occur at a younger age than a selected cut-off.

prevalence: Refers to the existence of a disease or event, whether or not it is newly occurring; the prevalence rate is the number of cases existing at a point in time (point prevalence) or over a specified time period (period prevalence).

principal diagnosis: The diagnosis established after study to be chiefly responsible for an episode of admitted patient care, an episode of residential care, or an attendance at the health care establishment. 

rate: A rate is one number (the numerator) divided by another number (the denominator). The numerator is commonly the number of events in a specified time. The denominator is the population at risk of the event. Rates (crude, age-specific and age-standardised) are generally multiplied by a number such as 100,000 to create whole numbers.

redistribution: A method in a burden of disease study for reassigning deaths with an underlying cause of death that is not in the study’s disease list. Typically, the deaths reassigned include: those with a case that is implausible as an underlying cause of death; those that relate to an intermediate cause in the chain of events leading to death; or those for which there is insufficient detail to ascertain a specific cause of death.

reference life table: A table that shows, for each age, the number of remaining years a person could potentially live, to measure the years of life lost from dying at that age.

relative risk: The risk of an event relative to exposure, calculated as the ratio of the probability of the even occurring in the exposed group to the probability of it occurring in the non-exposed group.

risk exposure distribution: The measure of the spread or distribution of exposure to the risk factor in the population that have encountered, experienced, or have the risk factor.

risk factor: Any factor that causes or increases the likelihood of a health disorder or other unwanted condition or event.

risk–outcome pair: Associates a condition in the disease list with a known risk factor for that condition.

sequelae: Health consequences of diseases and injuries, such as heart failure due to coronary heart disease. Each sequela may be mapped to one or more health states.

theoretical minimum risk exposure distribution (TMRED): The risk factor exposure distribution that will lead to the lowest conceivable disease burden.

years lived with disability (YLD): Measures the years of what could have been a healthy life that were instead spent in states of less than full health. YLD represent non-fatal burden.

years of life lost (YLL): Measures years of life lost due to premature death, defined as dying before the global ideal life span at the age of death. YLL represent fatal burden.