Module Components

• Learning Activities

Topics

• Critical Appraisal Principles
• Systematic Review Appraisal
• Randomized Control Trial Appraisal
• Cohort Study Appraisal
• Case Control Study Appraisal
• Module 8 Self-Review

NDNP 802-Methods for Evidence-Based Practice

Module 8: Critically Appraising Quantitative Evidence

Cohort Study Appraisal

A cohort study, also known as a follow-up or longitudinal study, is another observational study design. In this study a population who do not have the health outcome or disease of interest are first divided into those who are exposed to a risk factor and those who are not. Alternatively exposed and unexposed populations may be chosen separately. Irrespective, both groups are then followed, often over long periods of time. At the end of the period of observation the incidence of disease or frequency of health outcome in the exposed group is compared to that in the unexposed group. The study is generally prospective as it looks forward from potential cause to consequence.

Advantages

• Subjects in cohorts can be matched, which limits the influence of confounding variables
• Standardization of criteria/outcome is possible
• Easier and cheaper than a randomized controlled trial (RCT)

Disadvantages

• Cohorts can be difficult to identify due to confounding variables
• No randomization, which means that imbalances in patient characteristics could exist
• Blinding/masking is difficult
• Outcome of interest could take time to occur

Example

• Ramchand, R., Ialongo, N. S., & Chilcoat, H. D. (2007). The effect of working for pay on adolescent tobacco use. American Journal of Public Health, 97(11), 2056-2062.

This study uses data collected from high school students from Baltimore, Maryland, and studies the differences in initiation of tobacco use between a cohort of adolescents that started working for pay and a cohort of adolescents that did not work. The results suggest that adolescents who work for pay have a higher risk of initiating tobacco use.

Cohort Study Critical Appraisal Tool - See "Tool" in Lesson Plan under "Recommended Reading"