A large, multi-country study is conducted to determine the effect of economic development on cancer incidence and mortality. The study uses data obtained from the national cancer registries, along with information regarding per capita gross domestic product as reported by the International Monetary Fund and life expectancy as reported by the World Health Organization. Which of the following best describes the design of this study?

Question

A large, multi-country study is conducted to determine the effect of economic development on cancer incidence and mortality.  The study uses data obtained from the national cancer registries, along with information regarding per capita gross domestic product as reported by the International Monetary Fund and life expectancy as reported by the World Health Organization.  Which of the following best describes the design of this study?

Quizplus · Accepted Answer

This observational study is analyzing population-level data to evaluate the association between a potential exposure (eg, low socioeconomic status population) and a given outcome (eg, increased cancer mortality). Using population-level (rather than individual-level) data as a unit of analysis in such a manner is consistent with an ecological study. Ecological studies are useful for generating hypotheses but should not be used to draw conclusions regarding individuals within these populations (ecological fallacy). (Choices A and B) Case-control and cohort studies deal with individuals rather than populations. In case-control studies, the odds of exposure to a certain characteristic (eg, personal socioeconomic status) are compared between affected individuals (eg, patients with cancer) and unaffected individuals who serve as controls. In cohort studies, individuals with and without different exposures (eg, high or low personal socioeconomic status) are followed over time to determine the incidence of the disease of interest (eg, cancer). (Choice C) Cross-sectional surveys evaluate the exposures and outcomes of interest in individuals (not populations) at a given point in time ("snapshot"). The overall design of this multi-country study relies on population-level data, not individual-level data. (Choice E) Nested case-control studies start with cohort studies in which participants are followed over time; those participants who develop an outcome of interest become cases for a case-control study. (Choice F) Qualitative studies use focus groups, interviews (structured and semi-structured), and other anthropologic techniques to obtain narrative information for explaining quantitative results. (Choice G) Randomized controlled trials randomly assign subjects into a treatment group or a control group. The groups differ only in the intervention (treatment) of interest. (Choice H) Systematic reviews and meta-analyses combine the results of several published studies (with an emphasis on high-quality, randomized controlled studies) to estimate the pooled effect. Educational objective: The unit of analysis in ecological studies is populations rather than individuals.

A Large, Multi-Country Study Is Conducted to Determine the Effect