4 - Healthy research: study designs for public health

Summary

Box 4.1 Oranges and lemons

In 1747, James Lind conducted an experiment to test six different cures for scurvy. While at sea, he identified 12 patients with scurvy whose ‘cases were as similar as I could find them’ and prescribed a different treatment to each pair of patients. After a few days he found that the two patients fortunate enough to have been prescribed oranges and lemons were almost fully recovered whilst no improvement was seen in the other ten, who had been subjected to various regimens including sea-water, gruel, cider and various elixirs. From this, Lind inferred that inclusion of citrus fruit in the diet of sailors would not only cure, but also prevent scurvy. Limes or lime juice thus became a part of the diet on ships, earning British sailors their nickname of ‘limeys’

(Lind, 1753).

When we discussed what epidemiologists do in Chapter 1, we touched on some of the different types of study that we use to collect the information we need to answer questions about health. In Chapter 3 we looked at the descriptive studies that provide the ‘bread-and-butter’ information of public health; in this chapter we will look at the analytic studies that are our main tools for identifying the causes of disease and evaluating health interventions. Unlike descriptive epidemiology, analytic studies involve planned comparisons between people with and without disease, or between people with and without exposures thought to cause disease.