Types of Research

The field of medicine is dynamic, and our understanding and practices are always evolving. Doctors are continuously conducting new research and publishing their findings in peer-reviewed journals. This adds to scientific knowledge, but it’s also of great interest to the public, so medical research often shows up in the news and other media sources. You might be interested in research if you work as a health professional so that you can give evidence-based advice to others. Making sense of science requires that you understand the types of research studies used and their limitations.

THE HIERARCHY OF EVIDENCE

Researchers use many different types of study designs depending on the question they are trying to answer, as well as factors such as time, funding, and ethical considerations. The study design affects how we interpret the results and the strength of the evidence as it relates to real-life nutrition decisions. It can be helpful to think about the types of studies within a pyramid representing a hierarchy of evidence, where the studies at the bottom of the pyramid usually give us the weakest evidence with the least relevance to real-life decisions, and the studies at the top offer the strongest evidence, with the most relevance to real-life decisions.

The pyramid also represents a few other general ideas. There tend to be more studies published using the methods at the bottom of the pyramid, because they require less time, money, and other resources. When researchers want to test a new hypothesis, they often start with the study designs at the bottom of the pyramid, such as in vitro, animal, or observational studies. Intervention studies are more expensive and resource-intensive, so there are fewer of these types of studies conducted. But they also give us higher-quality evidence, so they’re an important next step if observational and non-human studies have shown promising results. Meta-analyses and systematic reviews combine the results of many studies already conducted, so they help researchers summarize scientific knowledge on a topic.