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Association Between Maternal Manganese Exposure and Pediatric Impaired Motor Development

Background

Part 1 

Questions 1-5:  A study was conducted to look at the association between history of maternal consumption of water contaminated with manganese during pregnancy and pediatric impaired motor development at age 4.  Manganese is a metal often found in water from very deep wells.  You are concerned that people who can afford to have deep wells dug (those exposed) may be wealthier, and therefore, they may have better nutrition during pregnancy.  Poor prenatal nutrition has been implicated as a risk factor for numerous neurological diseases and may change the effect of manganese on impaired motor development.  Children were classified as either having an impaired motor development or not having an impaired motor development.  Their mothers were interviewed about their past manganese exposure during the pregnancy of this child.  The resulting data are below in tables 1a and 1b.  Use this information to answer questions 1-5: 

Table 1a. Crude Analysis: Association between maternal consumption of contaminated water and pediatric impaired motor development

 

Motor Development Impairment (D+)

Healthy (D-)

Total

Manganese exposure(E+)

107

 

156

 

263

 

No manganese exposure

(E-)

85

 

528

 

613

 

Total

192

 

684

 

876


Table1b. Stratified Analysis: Association between manganese exposure and pediatric motor development impairment, stratified by nutrition

 

Good Nutrition

 

Poor Nutrition

Manganese exposure

Motor Development Impairment (D+)

Healthy (D-)

Total

 

Motor Development Impairment (D+)

Healthy (D-)

Total

Yes (E+)

10

45

55

 

97

111

208

No (E-)

35

173

208

 

50

355

405

Total

45

218

263

 

147

466

613

Odds Ratio (Calculate the stratum-specific odds ratios for nutrition and write them on the correct lines provided here and also for Q3 below.

 

 

_______

 

 

 

________


1. What type of epidemiological study design is described in the scenario above? 

a.Case-control study

b.Cohort study

c.Randomized control trial

d.Ecological study

2.   Using the results of the crude analysis (Table 1a), what is the unadjusted (crude) odds ratio for the association between maternal manganese exposure and pediatric motor development impairment? 

a.(107X528)/(156X85) = 4.26

b.(107 x 156)/(85 x 528) = 0.37   

c.(107/263)/(85/613) = 2.86

d.(170*263)/(85*613) = 0.86   

e.(107/263)/85/613)= 2.93

3.Calculate the stratum-specific odds ratios.  Write them below this question with the correct labels and then also write them in the correct cells on the crosstab above on the red lines provided. 

4. Assuming that poor nutrition is NOT on the causal pathway between manganese and motor development impairment, what might your initial hunch be before you run additional analyses?  

a.Nutrition appears to act as a mediator in the association between manganese and motor development impairment

b.Nutrition appears to act as an effect modifier in the association between manganese and motor development impairment

c.Nutrition influenced the response about manganese exposure and led to information bias.

d.Nutrition appears to be confounding the association between manganese exposure and impaired motor development.

5. Suppose you then ran the required additional analysis and were able to confirm your initial hunch that you stated in the previous question.  Based on the study results, what measure of association would you report to best describe the association between manganese exposure and motor development impairment?

a.The crude odds ratio

b.The odds ratios stratified on nutrition 

c.The adjusted odds ratio, adjusting for nutrition 

d.None of the above

6.  Researchers conduct a study on adults over the age of 45 to determine whether an association exists between meditation sessions and heart disease. They report that those who engage in daily meditation sessions have a risk ratio of 0.6 in developing heart disease over 10 years as compared to those who do not engage in daily meditation sessions. The 95% confidence interval had a range from 0.2 to 1.2. Select the correct statement solely based on the information provided in this scenario:

a.The authors should fail to reject the null hypothesis.

b. A Type I error could have occurred. 

c. The study had sufficient power to detect a true difference of at least 0.6. 

d. The researchers are confident that daily mediation sessions would protect against heart disease in at least 95 out of 100 studies, if conducted similarly. 

e. The authors should have reported a 90% confidence interval to obtain statistical  significance. 

7.   If the null value of 1 does NOT fall within a 95% confidence interval around a point estimate (such as a risk ratio) then the p-value must be:

a. less than or equal to 0.05

b. greater than 0.05

Part 2

8. In a study of the association between chewing tobacco and oral cancer, individuals with oral cancer were more likely to misreport that they chewed tobacco than individuals without oral cancer.

a. What type of misclassification is this?  Be sure to state whether it is differential or non-differential, AND whether it is misclassification of the exposure or the disease in your  response. Justify your response. 

b. How would this misclassification bias the OR you calculate using your study findings?  

Be sure to state whether you think it would bias the OR toward and/or away from the null value of 1 in your response.  

Part 3

To obtain full credit on this SPSS section, be sure to do as follows:

1.Express your responses in complete sentences.  Don’t just write the value of your answer under question.

2.Highlight, bold, or underline the actual values on the SPSS output provided to indicate your answers under each question.

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