Natural history of disease

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The natural history of disease is the course a disease takes in individual people from its pathological onset ("inception") until its resolution (either through complete recovery or eventual death).^[1] The inception of a disease is not a firmly defined concept.^[1] The natural history of a disease is sometimes said to start at the moment of exposure to causal agents.^[2] Knowledge of the natural history of disease ranks alongside causal understanding in importance for disease prevention and control. Natural history of disease is one of the major elements of descriptive epidemiology.^[2]

As an example, the cartilage of the knee, trapeziometacarpal and other joints deteriorates with age in most humans (osteoarthritis). There are no disease-modifying treatments for osteoarthritis---no way to slow, arrest, or reverse this pathophysiological process. There are only palliative/symptomatic treatments such as analgesics and exercises. In contrast, consider rheumatoid arthritis, a systemic inflammatory disease that damages articular cartilage throughout the body. There are now treatments that can modify that auto-immune inflammatory process (immune modulating drugs) that can slow the progression of the disease. Because these medications can alter the natural history of disease, they are referred to as disease-modifying antirheumatic drugs.^[3]

The subclinical (pre-symptomatic) and clinical (symptomatic) evolution of disease is the natural progression of a disease without any medical intervention. It constitutes the course of biological events that occurs during the development of the origin of the diseases^[4] (etiologies) to its outcome, whether that be recovery, chronicity, or death.^[5]

In regards to the natural history of disease, the goal of the medical field is to discover all of the different phases and components of each pathological process in order to intervene as early as possible and change the course of the disease before it leads to the deterioration of a patient's health.^[6]

There are two complementary perspectives for characterizing the natural history of disease. The first is that of the family doctor, who, by means of detailed clinical histories of each patient, can determine the presence of and characteristics of any new health problems. In contrast to this individualized view, the second perspective is that of the epidemiologist, who, through a combination of health records and biostatistical data, can discover new diseases and their respective evolutions, which is more of a population view.