Which of the following is true of this study? Check all that may apply.

In this example, the authors analyze the mortality (outcome) associated with different levels of coffee consumption (exposure). They haven’t recruited people based on their mortality! Since this is an observational study design, it is more likely to have bias (more in the next module) than a randomized controlled trial. The authors have not randomized people to consume different amounts of coffee here.

Types Of Medical Studies » Week 4 » Understanding Medical Research: Your Facebook Friend Is Wrong

Q: The following is the title of the study: Association of Coffee Drinking With Mortality by Genetic Variation in Caffeine Metabolism Findings From the UK Biobank What is the outcome of interest?

This title tells you that the authors studied the effect of coffee drinking on the outcome of mortality using data obtained from the UK Biobank cohort.

Q: The authors state that “We used baseline demographic, lifestyle, and genetic data from the UK Biobank cohort, with follow-up beginning in 2006 and ending in 2016, to estimate hazard ratios (HRs) for coffee intake and mortality, using multivariable-adjusted Cox proportional hazards models.” What is the type of study design used here?

This is a prospective cohort study because the researchers were actively enrolling people and following them along time to assess the development of the outcome. Specific measurements were taken along the way too, including caffeine intake and genetic profiles. This is not retrospective because it hadn’t already occurred in the past when the researchers got involved. It is not cross-sectional either because it analyzes individual people across a long span of time.

Q: Let's assume that the study researchers now want to analyze the effect of caffeinated coffee intake on a person’s wakefulness. They decide to randomize people into two groups — the study group will drink instant coffee and the control group will drink a placebo drink. What can be a good placebo drink option here?

A placebo is something that tastes very similar to the study drug (in this case, similar to coffee) but produces no effects in the body. Since the authors want to analyze the effect of caffeinated coffee on a person’s wakefulness, a suitable placebo might be coffee that tastes exactly the same as the study group’s coffee but has no caffeine. Tea or water will not make suitable placebos because they taste very different than coffee and the control group will be able to discern that they are the control group. A different type of coffee that has caffiene in it will not be a good control group either because it would have caffeine!

Q: Let’s assume that you are now assigned as the Caffeine Expert at the International Alliance on All Things Coffee (IAATC). The IAATC asks you to collect the highest-quality evidence to showcase the health effects of coffee. What is the best strategy to put together the highest form of evidence to support this stance?

The best form of evidence-based studies is usually a meta-analysis, where different results obtained from studies that study the same association are aggregated together. If you are able to find various studies that study the health effects of coffee, you can aggregate them together to present the best form of evidence! Just presenting this paper will probably not be as effective because it may be biased or may not be wholly representative. Conducting a whole new study will cost a lot of time and money and probably will not be as effective either. While you can always create a powerpoint showcasing human stories, it will not be qualified as scientific evidence to portray the health effects of coffee.