When I tell people I’m working toward my PhD in epidemiology, their responses are often “so you’re getting your degree in… skin?” Then I have to explain that, no, epidemiology is actually part of public health. Then I have to stumble through some sort of disjointed explanation that invariably ends with me receiving a whole bunch of questions about whether or not they’re going to be infected with H1N1. So, I thought I’d get the word out about what epidemiologists study.

Epidemiology is “the study of the nature, cause, control and determinants of the frequency and distribution of disease, disability and death in human populations.” In plain English, this means that epidemiologists are interested in why one person gets a disease and another person doesn’t. Epidemiology follows the assumption that disease doesn’t occur at random, and looks to identify the causal and preventive factors of disease.

While epidemiology has its roots in infectious disease outbreaks such as the cholera epidemic in London in the mid-1800s, epidemiologists today study all kinds of illnesses. Since the “epidemiological transition” in developed countries, when deaths due to infectious diseases decreased and deaths due to chronic diseases took over the greatest proportion of mortality, there has been growing interest in disciplines such as nutritional epidemiology and cardiovascular epidemiology.

How do epidemiologists find the answers to their questions about disease distribution? Most often, observational studies are performed to compare the rate of disease occurrence in individuals with a particular exposure with the rate of disease in those who haven’t been exposed. This exposure could be an environmental toxin, smoking or even drinking coffee. These relative risks are combined with evidence such as temporality, biologic plausibility and specificity of association to determine whether there is a causal relationship. Epidemiologists work in hospitals, research institutions and government institutions such as the Centers for Disease Control.

Epidemiology has become a part of nearly every discipline of the medical field, helping to find vital information on health and disease in the population. So next time you read about a study on CNN.com that tells you that alcohol and dark chocolate are good for your heart (both true!), you can thank an epidemiologist. Also, an undergraduate epidemiology course is now available on the River Campus; check it out!