A disease is defined as a physical or mental disturbance involving symptoms (such as pain or feeling unwell), dysfunction or tissue damage that may lead to ill health. Diseases can be acute (coming on sharply, often brief, intense and/or severe) or chronic (long-lasting with persistent effects ranging from mild to severe) or, in some cases, both. Common features of chronic diseases include:

  • complex causality, with multiple factors leading to their onset
  • a long development period, for which there may be no symptoms
  • a prolonged course of illness, perhaps leading to other health complications
  • associated functional impairment or disability.

Chronic diseases can range from mild to more significant conditions and include:

  • cardiovascular conditions (such as coronary heart disease and stroke)
  • cancers (such as lung and colorectal cancer)
  • mental disorders (such as depression)
  • diabetes
  • respiratory diseases (including asthma and chronic obstructive pulmonary disease)
  • arthritis, osteoporosis and other musculoskeletal conditions
  • chronic kidney disease
  • oral diseases (such as tooth decay and gum disease).

Changes to our lifestyles and reduction in other diseases in the last hundred years have meant that chronic diseases are increasingly common and now cause most of the burden of ill health. In addition to the personal and community costs, chronic diseases result in a significant economic burden because of the combined effects of health-care costs and lost productivity from illness and death. A key focus of the Australian health system, therefore, is the prevention and better management of chronic disease to improve health outcomes.