What are key principles of observational studies?

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Key Points

• An observational study is the most common type of study in health research.
• In an observational study, the researcher does not make any intervention, they only observe the participants’ exposure and outcomes in natural situations.
• Observational study is the choice of study in medical science when there is an ethical issues in Randomized Clinical Trial (RCT).

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Helpful Links, Videos and Online Courses

Overview

• Introduction – Observational Studies in a Learning Health System
  • This workshop summary focused on basic introduction of observational studies design in health care.
• Types of Observational Studies in Medical Research
  • An article from Research Gate that introduces various types of observational studies and the importance of observational studies in medical science. (Note: viewers do not need to create a ResearchGate account to access the article. Download as a PDF or view for free.)

Videos

• Observational Studies
  • A 5-minute video from the Health Research Group that clarifies the different kinds of observational studies. Useful for beginner researchers as it focused on basic concepts of observational studies.

• Understanding Observational Research
  • A very short, two-minute introduction from the National Pharmaceutical Council that provides comprehensive understanding and importance of observational studies from an expert.

• Medical Statistics – Part 7: Odds Ratios and Relative Risk in Observational Studies
  • A statistical overview of observational studies with various examples

Online Courses

• Introduction to Observational Studies
  • A series of videos on statistical models and measures, including those used for observational research, are available with free access through this program from Bristol University.

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Relevant Publications

• Thomas, J., Liew, D. & Hopper, I. (2018). Observational studies and their utility for practice. Australian Prescriber, 41(3): 82-85.
• Gail, M. H., Altman, D. G., Cadarette, S. M., Collins, G., Evans, S. J. W., Sekula, P., Williamson, E., & Woodward, M. (2019).  Design choices for observational studies of the effect of exposure on disease incidence. British Medical Journal, Open. e031031.
• Lao, K. S. J., Chui, C. S. L., Man, K. K. C., Lau, W. C. Y., Chan, E. W. & Wong, I. C. K. (2016). Medication safety research by observational study design. International Journal of Clinical Pharmacology 38: 676–684.
• Mann, C.J. (2012). Observational research methods-Cohort studies, cross-sectional studies, and case-control studies. African Journal of Emergency Medicine 2(1): 38-46.

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What are cohort studies and why are they important?

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Key Points

• Cohort studies are a type of longitudinal study in which a group of people with a common characteristic is followed over a time period to investigate predictive risk factors and health outcomes.
• A cohort study investigates the incidence of disease in exposed and unexposed groups with the risk factors.
• A cohort study is the most reliable type of observational study.

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Helpful Links, Videos and Online Courses

Overview

• What are Cohort Studies?
  • Describe basic concepts of cohort studies including strengths and limitations.
• Cohort Studies
  • Overview of cohort study designs with various examples of prospective and retrospective cohort studies.
• Cohort Studies
  • This University of North Carolina Gillins School of Global Public Health ‘ERIC Notebook’ introduces statistical analysis methods for cohort studies with various examples.

Videos

• The Cohort Study – Population Health: Study Design
  • Explains the basic concepts of a cohort and differentiates between prospective and retrospective cohort studies with examples.
• Cohort Studies
  • Dr. Danial Whelam teaches an overall introduction of a cohort study.
• Cohort Studies – Basic Study
  • Harvard School of Public Health’s video series explains an overview of cohort studies with examples.

Online Courses

• Cohort Studies
  • A series of videos are available (free access) through this program on different types of research methods and statistics.

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Relevant Publications

• Setia, M. S. (2016). Methodology series module 3: Cohort studies. Indian Journal of Dermatology, 61(1): 21–25.  
• Wang, X.  & Cheng, Z. (2020). Cohort studies: Design, analysis, and reporting. Chest Journal, 158(1S): S72-S78. 
• Aronsson, J., Clarke, D., Grose, J., & Richardson, J. (2020). Student nurses exposed to sustainability education can challenge practice: A cohort study. Nursing and Health Sciences, 22(3): 803–811.

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What are cross-sectional studies and why are they important?

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Key Points

• Cross-sectional studies take place at a single point in time; researchers assess exposure and health outcomes at the same time.
• Cross-sectional studies are conducted to determine the prevalence of diseases in the given time.
• Cross-sectional studies are comparatively cheaper and less time-consuming.

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Helpful Links, Videos and Online Courses

Overview

• What is a Cross-sectional Study?
  • Introduces an overview of cross-sectional study design and its uses.
•  Study Design: Cross-sectional Studies  
  • Describes the importance, uses, and limitation of cross-sectional study design with examples.
• Cross-sectional Studies
  • This University of North Carolina Gillings School of Global Public Health ‘ERIC Notebook’ introduces a statistical analysis of cross-sectional studies with various examples.

Videos

• Cross-sectional Studies
  • This Harvard School of Public Health’s video series explains an overview of cross-sectional studies with examples.
• Cross-Sectional Studies in 5 minutes
  • Explains the process of conducting cross-sectional studies with various examples.  

Online Courses

• Cross-sectional Studies
  • In this Coursera course, presented by faculty from the University of North Carolina Gillings School of Global Public Health, the Week 3 content reviews study designs, and compares cross-sectional study design with other observational study designs, and includes examples.
  • As with other Coursera courses, an account is required, but the content is free. If you would like to have a certificate of completion, there may be a small fee.
• Cross-sectional Studies
  • A series of videos are available (free access) through this program on different types of research methods and statistics.

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Relevant Publications

• Kesmodel, U. S. (2018). Cross-sectional studies: What are they good for? Acta Obstetricia et Gynecologica Scandinavica, 97(4), 388–393.
• Setia, M. S. (2016). Methodology Series Module 3: Cross-sectional Studies. Indian Journal of Dermatology, 61(3): 261–264.
• Wang, X. & Cheng, Z. (2020). Cross-sectional studies: Strengths, weaknesses, and recommendations. Chest, 158(1S), S65-S71.

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What are case-control studies and why are they important?

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Key Points

• A case-control study is a type of observational study. Observational studies do not involve any intervention or action to change the course of the illness. 
• Case-control studies are designed to understand if a certain exposure (for example tobacco) is associated with developing a disease or condition (such as lung cancer).
• Study participants are selected based on whether they have the disease or condition of interest.  If they do have the disease or condition, they are called cases.  If they do not have the disease or condition, they are called controls. 

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Helpful Links, Videos and Online Courses

Overview

• A Practical Overview of Case-Control Studies in Clinical Practice
  • A guide for understanding the general overview of case-control studies. 
• Epidemiology in Practice: Case-Control Studies
  • Helps in understanding the brief introduction of the case-control study and also about investigating risk factors and sampling. 
• Observational Research Methods: Cohort, Cross-sectional, and Case-control Studies
  • A comprehensive guide for understanding advantages and disadvantages, and overcoming sampling bias in these study designs.

Videos

• “Case-Control Study” in 10 Minutes
  • Gives a brief overview of case-control study designs with an example.
• Case-Control Studies: A Brief Overview
  • A guide in understanding general design principles of case-control studies, when case-control designs are more useful than cohort studies, and strengths and weakness of case-control studies. 
• Case-Control Study – Intro
  • A brief overview of case-control study designs.

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Relevant Publications

• Menya, D., Oduor, M., Kigen, N., Maina, S. K., Some, F., Kibosia, C., Chumba, D., Mugor, F. A., Carel, R. S., Middleton, D. R. S., Abebi-Ardekani, B., Schüz, J. & Cormack, V. A. (2018). Cancer epidemiology fieldwork in a resource-limited setting: Experience from the western Kenya ESCCAPE esophageal cancer case-control pilot study. Cancer Epidemiology, 57, 45–52. 
• Landy, R., Sasieni, P. D., Mathews, C., Wiggins, C. L., Robertson, M., McDonald, Y. J., Goldberg, D. W., Scarinci, I. C., Cuzick, J. & Wheeler, C. M. for the New Mexico HPV Pap Registry Steering Committee. (2020). Impact of screening on cervical cancer incidence: A population-based case-control study in the United States. International Journal of Cancer, 147(3), 887–896. 

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