MATH6033 Assignment: Cardiovascular Risk and Tea Drinking: Epidemiological Analyses

MATH6033 Epidemiological Methods – Assignment 2025

This assignment will constitute 100% of your overall mark for this course. Both questions should be attempted, and each part will contribute towards 50% of the marks. The marks available for each question are given as an approximate guide to the amount of work that is required from you.

Page limit

Your solution to Part 1 should not exceed four A4 sides, your solution to Part 2 should not exceed three A4 sides (including tables). Please start Part 2 on a new page. These limits assume that a sensible font size has been used e.g. Times New Roman size 12, or Arial 11, and that standard margins are used (i.e. 2.54cm around the text). Font size and margins can be reduced if necessary for tables, but not otherwise. Marks will be deducted for work exceeding the stated page limits.

Please note that good solutions could well be written up in fewer than the maximum allowable number of pages. Do not present extra work as appendices. Any appendix submitted will not be read and marks will be deducted for exceeding the page limits.

There is no need to include a cover sheet at the front of the assignment.

Working with other students

You are allowed to talk to your peers about the coursework, but you need to write up the solutions independently, i.e., while you are on your own. In particular, copying the solutions from a classmate or anywhere else would constitute a breach of academic integrity.

Artificial Intelligence tools

You must not submit work that has been created or part-created by Generative AI tools (such as ChatGPT) that you claim as your own work. Please abide by the University of Southampton generative AI guidelines:
Using generative artificial intelligence during your studies | University of Southampton

Submission format

You are advised to save and submit your final work in PDF format when submitting to Turnitin. This will ensure that any tables within submitted documents are correctly rendered in the Turnitin online viewer.

Filename

If your student number is 123456789 then it would be helpful if you could name your submitted file:
123456789_MATH6033assignment.pdf

Deadline

Submit your completed assignment on Turnitin on Blackboard by 3pm on Tuesday 6th May.

Work submitted after the deadline will have the final mark reduced as per the university regulations.

Queries

If you have any queries concerning this assignment, you should e-mail:

• Camille Pearse: cp@mrc.soton.ac.uk
• Stefania D’Angelo: sd@mrc.soton.ac.uk

Part 1 – Life course determinants of cardiovascular mortality and morbidity

Background

Life course epidemiology is the study of the effects of exposures acting during gestation, childhood, adolescence and adulthood on risk of morbidity (disease) and mortality (death) in later adulthood.

The study of the developmental origins of health and disease involves researching how poor growth of the fetus in the womb leads to permanent changes in the body’s function that cause increased rates of many different types of disease, including cardiovascular disease, in subsequent adult life.

The Hertfordshire Cohort Study was conducted to investigate the relationship between fetal growth (quantified by birth weight) and mortality in later adulthood.

The following tables present the standardised mortality ratios (SMRs) for:

• ‘All cardiovascular disease’ (ICD9 codes 390–459)
• ‘All other causes’ (ICD9 codes <390 or >459)

…by birth weight for 15,500 men and women in the 1911–1930 Hertfordshire birth cohort. The SMRs were calculated for mortality between 1951 and the end of 1992 using the person-years approach.

Your Task (Part 1a)

Enter the relevant data into Stata (hint: use the Data Editor – you open this by clicking the button on the top left-hand side of the screen that looks like a spreadsheet with a pencil over it).

1. Investigate whether for:
   (a) all cardiovascular disease, and
   (b) all other causes of death,
   there is evidence that the SMRs are homogenous across the birth weight groups, follow a linear trend, or are all different.
   Briefly present the deviance statistics, residual degrees of freedom, and deviance difference tests for the models that you fit. Summarise your findings in a few sentences providing a clear interpretation of the meaning of the models.
   (14 marks)
2. Calculate SMRs and associated 95% confidence intervals in each birthweight group for all cardiovascular disease and for all other causes of death.
   (4 marks)

Further Background

The Hertfordshire study was unable to account for other life course factors which may influence risk of cardiovascular morbidity and mortality. Adjustment for such factors might have altered the conclusions of the study if they acted as confounders of the relationship between birth weight and cardiovascular disease.

Accordingly, a further study was carried out to explore the relationship between fetal growth (quantified by birth weight) and high blood pressure; this study included information about adult risk factors.

Elevated blood pressure is one form of cardiovascular morbidity; over time, it leads to arterial and organ damage and increased risk of stroke, kidney problems and heart failure.

Identification and management of factors that influence blood pressure is an important public health issue.

Data

The participants for this study were 712 men and women born in Sheffield between 1923–1930 and still living in the area in the mid-1990s.

The Stata file sheffield.dta contains the variables:

• idnum – Study ID number
• sex – Sex (1 = Male, 2 = Female)
• bwt – Birth weight (oz)
• smokstat – Smoking status (0 = Never, 1 = Ex, 2 = Current)
• sbp – Systolic blood pressure (mmHg)
• bmi – BMI (kg/m²)

Your Task (Part 1b)

Answer the following questions to explore the risk factors for blood pressure in this cohort of elderly men and women.

3. Examine the distributions of the outcome variable (systolic blood pressure) and the primary exposure variable (birthweight) to determine whether any transformations of these data are required for use in subsequent linear regression analyses. Present appropriate summary statistics of location and spread to describe the distributions in these subjects.
   (5 marks)
4. Smoking, gender and body mass index are all potential risk factors for blood pressure. Explore the univariate associations of each of these risk factors with birthweight.
   (3 marks)
5. Is there a difference in systolic blood pressure between men and women? Comment on what impact you expect gender to have on the birth weight–blood pressure relationship.
   (4 marks)
6. Use linear regression to describe the magnitude and direction of relationship between systolic blood pressure and birth weight in this cohort. Present the results of appropriate statistical analyses to determine if gender is a confounder, or if there is an interaction with gender.
   (4 marks)
7. Describe the relationship between systolic blood pressure and smoking. Determine if gender is a confounder, or if there is an interaction with gender.
   (6 marks)
8. Select a final multiple linear regression model that you think best summarises the relationship between systolic blood pressure and birth weight in these subjects, taking account of any other potential risk factor(s) you now think important. Briefly explain your reasons for including/excluding gender, body mass index, and smoking status in your chosen model. A non-statistical but numerate colleague needs to understand the results; interpret the model in a way that he/she would understand.
   (10 marks)

(50 marks in total for Part 1)

Part 2 – Tea drinking habits and oesophageal cancer in a high-risk area in northern Iran: population-based case-control study

Background

A friend of yours in Southampton enjoys drinking tea, but has heard that tea drinking may be associated with cancer.

He has been searching on the internet and has found a paper published in the BMJ reporting on a study looking at the association between tea drinking and oesophageal cancer.

Your friend knows that you are studying statistics and have done a course in epidemiological methods and thinks that you might be able to help him understand the paper. He wants you to explain the paper but also to interpret the findings and help him decide whether he should change his tea-drinking habits.

A copy of the paper is attached.

Your task (Part 2)

Read the paper and answer the questions below. Remember your solution to Part 2 should not exceed three A4 typed sides.

Also remember that your non-statistical/epidemiological friend needs to have everything clearly explained in lay language so avoid using technical terms unless you explain them.

The clearer the explanation, the greater the number of marks that will be awarded for each part.

1. There are two parts to the study in this paper. Explain the two study designs and how they each contribute to answering the study question. What are the advantages and disadvantages of using the case-control study compared to others that are possible?
   (9 marks)
2. How were the cases and controls selected in the case-control study? Describe what matching means and why it is used. Were the methods of selecting cases and controls appropriate?
   (8 marks)
3. Explain what an odds ratio is and how you interpret it using an example of one of the crude odds ratios from Table 2.
   (5 marks)
4. Your friend does not understand what a confounding variable is. Explain, with the aid of tobacco intake as an example, what a confounding variable is and how the confounding variables have been accounted for in the analysis.
   (7 marks)
5. Summarise the message of the first two sections of Table 2 (those relating to tea temperature and interval between tea being poured and drunk).
   (6 marks)
6. Describe the evidence for whether you think the study conclusions are correct. Discuss whether the association between drinking hot drinks and oesophageal cancer is likely to be causal. Explain whether you think the findings are relevant to your friend and what (if any) changes he should consider to his tea-drinking habits.
   (15 marks)

(50 marks in total for Part 2)UAZH202504129327

Let me know if you’d like this formatted as a downloadable Word or PDF file too!

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