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Assignment 2: Data analysis

Purpose:This assignment assesses your ability to correctly analyse data, interpret what it means and relate it to your taught work.

Background: You have been given 2 research papers on separate but related topics. The following data has been extracted from these papers. Please look at the data and answer the questions relating to it, including in your answer information you have gained from reading the papers thoroughly. You will not get good marks simply from looking at the extracts – you need to read the papers themselves.

1. Mean systolic blood pressure differences between babies who were breastfed and those who were bottle fed (Martin et al, 2005; Figure 2).

Figure 2: Mean diastolic blood pressure differences between babies who were breastfed and those who were bottle fed (Martin et al, 2005; Figure 3).

Q1. Using the figures above and your reading of the paper, what are the main messages of the figures? Explain your answer. You must make reference in your answer to the effects of infant feeding upon systolic & diastolic blood pressures, commenting on effects of study size and duration of breastfeeding

Q2. What factors did the authors identify as potential explanations for the marked heterogeneity observed in studies on blood pressure and infant feeding, and why?

Q3. Why is raised blood pressure a public health concern, and how may breastfeeding affect risk?

Part 2: Duration of breastfeeding & risk of overweight (Table 1, McCrory & Layte, 2012). Use the table below to answer the following questions.

Q4. What is meant by an ‘odds ratio’ for overweight and obesity? Explain in the context of the table above.

Q5. What explanation(s) did the authors offer for their findings?

References

Martin RN, Gunnell D & Davey Smith G (2005) Breastfeeding in Infancy and Blood Pressure in Later Life: Systematic Review and Meta-Analysis. Am J Epidemiol 161(1): 15-26.

McCrory C & Layte R (2012) Breastfeeding and risk of overweight and obesity at nine-years of age. Social Science & Medicine 75: 323-330.

Useful information

Sedgwick P (2012) How to read a forest plot. BMJ 345:e8335

Sedgwick P (2012) Absolute and relative risks. BMJ 345:e5613

Sedgwick P (2012) Absolute and relative risks correction. BMJ 345:e6252

Sedgwick P (2012) Meta-analysis: tests of heterogeneity. BMJ 344:e3972

University of Nottingham (2007) RLO: Presenting and interpreting meta-analyses. Web access at http://www.nottingham.ac.uk/nmp/sonet/rlos/ebp/meta-analysis2/index.html

World Cancer Research Fund/American Institute for Cancer Research (2007) In: Food, nutrition, physical activity and the prevention of cancer: a global perspective. Second expert report. WCRF/AICR: Washington. Chapter 3: Judging the evidence p48-62.