I hear the terms terminal and chronic illness everywhere, and I have a vague idea of what they mean. How long are they expected to last? Can they be cured? Do they result in death?
Erm, the term chronic illness in itself isn't unambiguous, in the scientific literature it is used in different ways:
The academic literature is not immune to the same kind of terminology variation. Differences in how “chronic disease” is used are largely dependent on the data used for the research and the discipline of the lead authors (i.e., public health and sociology). [...] The implication of a non-uniform use of the term is that a detailed read of each study is necessary to avoid erroneous conclusions regarding interventions necessary to reduce chronic disease burden for the individual and society.
Popular Internet sources used by the general public to gather medical information use the terms “chronic disease” or “chronic condition” to mean slightly different things. For example, MedicineNet describes a chronic disease as,
- one lasting 3 months or more, by the definition of the U.S. National Center for Health Statistics. Chronic diseases generally cannot be prevented by vaccines or cured by medication, nor do they just disappear.
According to Wikipedia a chronic condition is,
- a human health condition or disease that is persistent or otherwise long-lasting in its effects or a disease that comes with time. The term chronic is often applied when the course of the disease lasts for more than three months. Common chronic diseases include arthritis, asthma, cancer, COPD, diabetes and viral diseases such as hepatitis C and HIV/AIDS.
Finally, the World Health Organization states that chronic diseases,
- are not passed from person to person. They are of long duration and generally slow progression. The four main types … are cardiovascular diseases (like heart attacks and stroke), cancers, chronic respiratory diseases (such as chronic obstructed pulmonary disease and asthma) and diabetes.
The CDC’s Chronic Disease Overview omits chronic respiratory conditions, such as COPD and asthma, and makes no mention of duration of the disease or symptoms. MedicineNet’s definition does not list specific diseases, but does include the phrase “cannot be cured by medication.” Similar to MedicineNet, Wikipedia uses the 3-month time span as a marker, but does list specific diseases, including HIV. The WHO’s definition would eliminate HIV as a chronic disease as the virus is “passed from person to person.”
The variation in meaning is amplified when viewed in an international context. For example, the Australian Institute for Health and Welfare includes the following as common features of chronic disease:
- 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.
Source: Bernell, Stefany and Howard, Steven. Use Your Words Carefully: What Is a Chronic Disease?. frontiers in Public Health, 2016,4,159. doi: 10.3389/fpubh.2016.00159
Summarising, an illness is usually considered to be chronic when it is
- long-lasting (3 months is used often)
- not simple to be cured
- a complex causality
A terminal illness on the other hand is an illness that can not be cured and is expecting to lead to the imminent death of the patient (NHS.uk).
Diseases exist that are both chronic and terminal, multiple sclerosis as an example. Chronic diseases can turn into terminal diseases if the progress to a state where they will inadvertently lead to death. HIV is one common example of a chronic disease that can become terminal.