Modern epidemiology involves history since finding the causes of chronic diseases requires looking back for decades.
In the past, infectious diseases, which were the leading cause of death, were the primary focus of epidemiological research. This was especially true after the advent of urbanization when populations began to concentrate in cities. Better hygiene, vaccination rates, and antibiotics were able to put an end to the epidemics.
Epidemiology gradually evolved into the study of the causes, the distribution, the risk factors, and the prevention of chronic diseases, but it also expanded to include the study of diseases with a mass occurrence at the population level, such as depression, and accidents. The medical community has slowly come around to the idea that diet plays a significant role in overall health, but they continue to give it less weight than it deserves.
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