Critical analysis of published research
Please note: Please include only the sections eg. “Part A (1) and your answers. Do not include the questions in your paper.
PART A (20 Marks)
Read the paper by Keirnan et al, and answer the following questions.
Kiernan et al. (1998) Characteristics of successful and unsuccessful dieters: An application of signal detection methodology. Annals of Behavioral Medicine 20(1):1-6
- 1. What is the study design? Justify your response (5 marks)
- 2. What was the control group in this study? (2 marks)
- 3. Why was the average BMI for both men and women so high in this study? (3 marks)
- 4. Why was smoking not considered as a confounder in the statistical analysis? (1 mark)
- 5. What was the prevalence of binge eating disorder in men and in women? (4 marks)
- 6. What were the strongest predictors of successful dieting? Outline the statistical substantiation for these. (5 marks)
PART B (20 Marks)
Read the paper by Sekhri and Kaur, and answer the following questions.
Sekhri K and Kaur K (2014). Public knowledge, use and attitude toward multivitamin supplementation: A cross-sectional study among general public. Int J Appl Basic Med Res. Jul- Dec; 4(2): 77–80. doi: 10.4103/2229-516X.136780
- 1. Identify the person, place and time for this study. With the ‘person’ describe the population that were surveyed in regard to ‘generalisability’ of the results (6 marks)
- 2. How and what data was collected? (4 marks)
- 3. What statistical associations did they find or not find in their results? (4 marks)
- 4. On what statistical basis did they decide there was no association? (1 mark)
- 5. Do you think these associations are conclusive based on the study methods? Answer should include comment on the population of people recruited. (5 marks)
PART C (20 Marks)
Read the extract of a paper below, and answer the questions that follow.
Title: Impact of Calcium and Magnesium in drinking water on Cardiovascular mortality in the
Background: Cardiovascular mortality represents the main cause of mortality in people over
65yrs of age. Previous studies have suggested an inverse relationship between the number of cardiovascular deaths and water quality. The aim of this study was to assess the relationship between cardiovascular mortality in the elderly and the concentration of calcium and magnesium in drinking water
Population and outcome: Our sample was composed of the populations living in 75 local communities in the south of France. The communities were chosen at random from all communities in South France. We considered the population between 1st January 2002 and 31st December 2008, aged over 65 years, and collected all deaths occurring in this population during
this time. The number of person-years was calculated using the average of the population between the two dates. We obtained the distribution of the population of the communities by age and sex from the national registry. The causes of death were as noted on the death certificate. For each death, we recorded age at death, sex, community of residence and main cause of death (based on ICD-10 codes). We observed 14,311 deaths, and the total number of person years was 777, 493.
Measurement of exposure: We divided each community into distribution zones, supplied by one particular water source, on the basis of information given by the sanitary administration. Two measurement surveys were carried out in 2003 to measure pH and concentrations of calcium and magnesium in each zone. For each water supply, the mean of the values for the two surveys we conducted, and of the routine measurements, collected by the sanitary admission between 2002 and 2005 were calculated. For each distribution zone, we computed average values for calcium and magnesium concentrations using the hourly flow or the relative contribution of each water source in the composition of drinking water in the zone. Six of the communities were excluded from the study because of recent changes in the distribution of water. Our final sample consisted of 69 communities for which data are available.
Analysis: Calcium and magnesium concentrations were categorised into 3 groups. The cut-off points were fixed at the tertiles values (ie divides the data into 3 equal groups, with one third of the data in each group).
Results: As mentioned previously, there were 69 communities, with 14,311 deaths, and the total number of person years was 777, 493. We observed a protective effect of higher calcium concentration (RR: 0.90; 95%CI 0.84-0.96) for concentrations levels greater than 94mg/l. We also found a protective effect of magnesium between 4 and 11 mg/l with a relative risk of 0.88
for women and 0.92 for men. The results are presented in table 1:
Conclusion: These findings suggest a protective effect of calcium in drinking water with a dose- response relationship. Magnesium seems to be protective on cardiovascular mortality for levels between 4-11mg/l
- 1. What type of study have the authors conducted? Justify your response. (3 marks)
- 2. The authors conclude a ‘dose-response’ relationship. What does this mean? What evidence do they have to support this claim? (3 marks)
- 3. Identify 2 main strengths and 2 main weakness of this study. Explain why you think they are strengths or weaknesses, and what the impact they have on the study/results/conclusion. (10 marks)
- 4. Given the results, do you think it is ethical to conduct a randomised controlled trial
investigating the relationship between magnesium and calcium in drinking water on deaths due to cardiovascular disease? Justify your response (4 marks)