Observational
and Interventional Epidemiology
 Begin
by reading this topic in the workbook (or online)
Another person whose name appears in the hall of epidemiological
fame is James Lind.
He was a physician in the early 18th century, when
was a major problem among sailors on long sea voyages. At that time,
the cause of scurvy was not known. Bad air, congenital laziness
and indigestible food were all suggested as possible causes. Lind
observed that the sailors' diet was very poor, consisting of biscuits
and salted fish or meat.
In 1747 he conducted an experiment at sea with 12 patients suffering
from scurvy.
MCQ question here
Lind's experiment is an early example of (also known as experimental epidemiology). Lind
divided his population into groups and allocated different treatments
to each. Effectively Lind allocated a specific exposure (type of
food supplement) to each group and then observed the outcome (whether
or not scurvy improved).
What was particularly important was that he had comparison or "control"
groups of patients who did not receive the intervention of interest,
which meant that he could compare the outcome in those who received
the intervention to those who did not.
Does Lind's experiment prove that oranges and lemons cure scurvy?
Write down some reasons for your answer before you answer the question.
More recently, the method of randomised trials was introduced,
in which participants are randomly assigned to receive the intervention
or an alternative, either a
or the standard treatment for the condition in question, which acts
as a control.
Randomised controlled trials were first used in the 1950s - an
early example was in the investigation the effect of streptomycin
in the treatment of tuberculosis. This method has been increasingly
used to evaluate new treatments and interventions since then.
We will discuss the role of chance in epidemiological studies in
a future session, intervention studies in Chapter 17, and how to
calculate sample sizes in the practical epidemiology study unit.
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Yes