Topic: the effectiveness of the use of insecticide-impregnated mosquito nets

Description: [?]
Preferred language style: English (U.S.)

just answer the qustions please
i study master of public health for subject name Epidemiology

SECTION A (30 marks)

The following studies were undertaken to examine the effectiveness of the use of insecticide-impregnated mosquito nets (IMNs) in decreasing the incidence of malaria. Malaria is a disease caused by a parasite that can be spread to humans if they are bitten by a mosquito carrying the malaria parasite. Unless otherwise stated, no household used IMNs prior to the study being conducted.

For each study, state what type of study it is and briefly (one or two sentences should be enough) justify your choice.

1) Children in the village who had not had malaria were randomised to one of two groups – sleep in a bed with an IMN or sleep with their usual sleeping arrangement. The occurrence of new cases of malaria over the following six months was determined for each group and compared.

2) A random sample of children in the village was chosen. The parents of the selected children were asked to buy an IMN and have their children sleep under it. Some bought the nets and some did not. The occurrence of new cases of malaria over the following six months was determined for those children whose parents bought a net and compared with the occurrence in children whose parents had not bought a net.

3) A year before, some villages in the country had been given access to IMNs and some had not. In the villages that did have access to IMNs, some of the parents obtained the IMNs and some did not. The occurrence of new cases of malaria in the previous six months was determined for those villages with access to IMNs and compared with the occurrence in those villages that did not have access to IMNs.

4) Eligible families had to have more than one child. They also had to have at least one child who had not had malaria. Children with a brother or sister who had been diagnosed with malaria were provided with an IMN. Children in other families were not provided with an IMN. The occurrence of new cases of malaria over the following six months was determined for each group and compared.

5) Some parents in the village had bought an IMN in the previous year. All new cases of malaria that occurred over the previous six month period in children aged less than 10 years and living in the village were identified. A random sample of children aged less than 10 years from the same village who had not had malaria was also chosen. The parents of the identified cases and the other selected children were interviewed to determine whether their children had slept under IMN in the previous six months. The relationship between use of an IMN and occurrence of malaria was then estimated.

6) The parents of a random sample of children in the village were interviewed. At the interview they were asked whether their children slept under an IMN and whether their children had been diagnosed with malaria within the previous six months. The relationship between use of an IMN and occurrence of malaria was then estimated.

7) Parents were asked to volunteer to allow their children to be included in the study. The children of the parents who volunteered were included in the study. These children were randomly assigned to either have an IMN or not. The occurrence of new cases of malaria over the following six months was determined for each group and compared.

8) The parents of a random sample of children in the village were interviewed. At the interview they were asked whether their children slept under an IMN.

SECTION B (30 marks)

A (fictitious) study was done to examine the association between exposure to a new chemical, Xydane, and breast cancer, in a group of 3200 female factory workers who were followed for 30 years. Xydane does not cause or protect someone from gaining weight.
The main results are shown in table below.

Breast Cancer No breast cancer Total
Exposed to xydane 137 1163 1300
Not exposed to xydane 54 1846 1900
Total 191 3009 3200

1) Calculate an appropriate measure of effect. Show your working. (5 marks)

2) Describe this result in words, as you would if you were explaining this result to a friend who is not a health professional. (4 marks)

Being overweight is known to increase the risk of breast cancer. 1000 of the workers exposed to Xydane were overweight, and 125 of these workers developed breast cancer. 400 of the workers not exposed to Xydane were overweight, and 24 of these workers developed breast cancer.

3) Draw separate 2×2 tables for overweight workers and non-overweight workers showing the relationship between Xydane exposure and breast cancer. (4 marks for each table)

4) Is there evidence of confounding in this study? Explain your answer both in terms of the relative risk estimates and the criteria for confounding. Show any relevant working. (11 marks)

5) Is there evidence of effect modification? Explain your answer in one or two sentences. (2 marks)

SECTION C (40 marks)

A study was undertaken of the effectiveness of a new style of wrist protector in decreasing the risk of significant wrist injury of skateboard riders. Significant wrist injury was defined for this study as documented fracture of the wrist or admission to hospital for care of a wrist injury. For the purposes of this question, accept that the only important known potential influences on risk of significant wrist injury are age, gender and experience.
Members of a local skateboard club who agreed to participate in the study were randomly assigned to one of two groups – Group A (the new style) or Group B (the person’s usual approach to wrist protection, which may have been to use a protector available in shops or not to use a protector at all). Randomisation was conducted using a simple random number list. Consenting subjects were assigned a number from this list, which they took to a second person, who checked whether that number was allocated to Group A or Group B. Those allocated to Group A were given a pair of the new wrist protectors. The club had 550 members, of whom 520 agreed to participate. Prior to randomisation 25 subjects withdrew for unknown reasons. After randomisation there were 245 subjects allocated to Group A and 250 subjects allocated to Group B. Inexperienced riders (those who had been riding for less than six months) were evenly distributed between the two groups and the average age of the subjects in the two groups was similar. It was clear to which group the subjects had been allocated because the new style wrist protectors were very different to other wrist protectors available at the time the study was conducted.
Subjects were followed for one year. During the year, 30 subjects formally withdrew from the study (25 from Group A and 5 from Group B) (for unknown reasons). Investigators lost contact with another 50 (23 from Group A and 27 from Group B). Subjects were interviewed again at the end of the study. At the interviews 25 subjects allocated to Group A admitted to not using the new style wrist protectors regularly and 10 subjects allocated to Group B said they had obtained the new style wrist protectors from a friend and has used the new style most of the time. These 35 subjects who had essentially swapped groups were excluded from the analysis because they did not complete the study as instructed. The final analysis was conducted on the remaining 172 members of Group A (12 of whom had a significant wrist injury) and the remaining 208 members of Group B (17 of whom had a significant wrist injury).

1) What is the study factor(s)? (2 marks)
2) What is the outcome factor(s)? (2 marks)
3) Draw a flow diagram that describes the selection of subjects into the study and what happened to these subjects throughout the study. (10 marks)
4) Identify the main strengths and weaknesses of this study in terms of SELECTION. You need to justify your decisions for each strength and each weakness. As a guide, you should only need about a page (certainly no more than two pages) to answer question 4. (26 marks)

CLICK BUTTON TO ORDER NOW