A study examined coffee consumption between 1980 and 2004 for 50,739 American nu
ID: 3127155 • Letter: A
Question
A study examined coffee consumption between 1980 and 2004 for 50,739 American nurses from the Nurses’ Health Study who were free from depressive symptoms at baseline in 1996. Ten years later, 2607 nurses had reported a diagnosis of depression and antidepressant use at some point. The study found that depression risk decreased with greater caffeinated coffee consumption (but not for decaf coffee consumption).
(a) What type of observation study is this? Explain your answer.
(b) The investigators state that “this study cannot prove that caffeine or caffeinated coffee reduces the risk of depression but only suggests the possibility of such a protective effect.“ Explain why this is the case.
(c) What would be a possible confounding variable for this study?
Explanation / Answer
The given question deals with the study of the coffee consumption of nurses over a period of time and their depressive nature were studied for observing any possible relationship between the caffeinine consumption and depression.
a.
The type of observational study that has been used here is Cohort stuyd or panel study, since in cohort study is a correlational study in which the patient under study is minutely studied and monitored over a given period of time, which is also the case here where the nurses consuming caffeinine is monitored over a period of time.
b.
The investigator stated that " this study cannot prove that caffeine or caffeinated coffee reduces the risk of depression but only suggests the possibility of such a protective effect", since in the experiment conducted no control group was kept to observe if the risk of depression is truly lowered by caffeine consumption or whether the risk of depression got lowered with time and work.
c.
The possible confounding variable is time, which correlates with both the caffeine consumption and the risk of depression, that is both the dependent and independent variables.
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