INTRODUCTION TO EPIDEMIOLOGY

Byrne M, Agerbo E, Bennedsen B, Eaton W, Mortensen P. Obstetric conditions and risk of first admission with schizophrenia: A Danish national register based study. Schizophrenia Research 2007; 97: 51-59.

Critically appraise the above article by answering the following questions. You may use additional source material as you need to.

QUESTION 1:
Describe the evidence presented in the paper you selected. Specifically address the following questions:
– What was the exposure or intervention?
– What was the outcome?
– What was the study design?
– What was the study population?
– What were the main findings?
Limit of 1 page. Please note: Only one page of text will be marked [20 marks]

QUESTION 2:
To what extent can the observed association between the exposure and outcome be attributed to non-causal explanations? This question relates to the internal validity of the study. Consider the following questions in your critique:
– Are the results likely to be affected by selection and/or measurement bias?
– Are the results likely to be affected by confounding?
– Are the results likely to be affected by chance variation?
Limit of 2 pages. Please note: Only 2 pages of text will be marked [30 marks]

QUESTION 3:
Do you think there is evidence of a causal association between the exposure and the outcome? Consider the following questions in your critique:
– Is there a temporal relationship between exposure and outcome?
– Is there a strong relationship between the exposure and the outcome?
– Is there a dose-response relationship between exposure and the outcome?
– Are the results consistent within the study?
Limit of 2 pages. Please note: Only 2 pages of text will be marked [30 marks]

QUESTION 4:
Do the findings accord with other evidence? Specifically:
– Are the findings consistent with other evidence, particularly evidence from studies of similar or more powerful study design?
– Are the results plausible in terms of a biological mechanism?
Limit of 1 page. Please note: Only one page of text will be marked [10 marks]

QUESTION 5:
Are the findings externally valid, that is generalisable? Specifically:
– Can the findings be applied to the source population from which the study population was derived?
– Can the study results be applied to other relevant populations?
Limit of 1 page. Please note: Only one page of text will be marked [10 marks]

Readings that we have used throughout the semester:
Essential epidemiology: an introduction for students and health professionals – Penny Webb, Chris Bain 2011 (electronic resource) – Chapters 6,7, 9, 9 & 10