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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Disease | 6/7 | https://en.wikipedia.org/wiki/Disease | reference | science, encyclopedia | 2026-05-05T07:27:57.596378+00:00 | kb-cron |
Epidemiology is the study of the factors that cause or encourage diseases. Some diseases are more common in certain geographic areas, among people with certain genetic or socioeconomic characteristics, or at different times of the year. Epidemiology is considered a cornerstone methodology of public health research and is highly regarded in evidence-based medicine for identifying risk factors for diseases. In the study of communicable and non-communicable diseases, the work of epidemiologists ranges from outbreak investigation to study design, data collection, and analysis including the development of statistical models to test hypotheses and the documentation of results for submission to peer-reviewed journals. Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic. Epidemiologists rely on a number of other scientific disciplines such as biology (to better understand disease processes), biostatistics (the current raw information available), Geographic Information Science (to store data and map disease patterns) and social science disciplines (to better understand proximate and distal risk factors). Epidemiology can help identify causes as well as guide prevention efforts. In studying diseases, epidemiology faces the challenge of defining them. Especially for poorly understood diseases, different groups might use significantly different definitions. Without an agreed-on definition, different researchers may report different numbers of cases and characteristics of the disease. Some morbidity databases are compiled with data supplied by states and territories health authorities, at national levels or larger scale (such as European Hospital Morbidity Database (HMDB)) which may contain hospital discharge data by detailed diagnosis, age and sex. The European HMDB data was submitted by European countries to the World Health Organization Regional Office for Europe.
=== Burdens of disease === Disease burden is the impact of a health problem in an area measured by financial cost, mortality, morbidity, or other indicators. There are several measures used to quantify the burden imposed by diseases on people. The years of potential life lost (YPLL) is a simple estimate of the number of years that a person's life was shortened due to a disease. For example, if a person dies at the age of 65 from a disease, and would probably have lived until age 80 without that disease, then that disease has caused a loss of 15 years of potential life. YPLL measurements do not account for how disabled a person is before dying, so the measurement treats a person who dies suddenly and a person who died at the same age after decades of illness as equivalent. In 2004, the World Health Organization calculated that 932 million years of potential life were lost to premature death. The quality-adjusted life year (QALY) and disability-adjusted life year (DALY) metrics are similar but take into account whether the person was healthy after diagnosis. In addition to the number of years lost due to premature death, these measurements add part of the years lost to being sick. Unlike YPLL, these measurements show the burden imposed on people who are very sick, but who live a normal lifespan. A disease that has high morbidity, but low mortality, has a high DALY and a low YPLL. In 2004, the World Health Organization calculated that 1.5 billion disability-adjusted life years were lost to disease and injury. In the developed world, heart disease and stroke cause the most loss of life, but neuropsychiatric conditions like major depressive disorder cause the most years lost to being sick.
== Society and culture ==