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Assignment 1: Reading Research Article

  • Read the following article andanswer the questions listed in Part 2 section of this document by typing your answers in the indicated places.
  • Save the document using the filename A1_YourLastNameandFirstInitial.doc and submit it through Blackboard Assignment Dropbox. If I were to submit this assignment my filename would be A1_ChangG.doc

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Part 1.

NCI Cancer Bulletin, December 2, 2008 • Volume 5 / Number 24

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After Menopause, Weight Affects Breast Cancer Rates More than Mammography Use

Women who are overweight or obese after menopause face an increased risk of breast cancer, but a large prospective cohort study indicates that the frequency of mammography use and screening accuracy are not the primary explanations for higher rates of breast cancer in these women. The same is true of large, invasive breast cancer tumors and advanced stage disease; risk increases with weight, but higher rates are not explained by the frequency or accuracy of screening mammography before breast cancer was diagnosed. The study appears in the December 3 Journal of the National Cancer Institute.

Dr. Karla Kerlikowske of the San FranciscoVeteransAffairsMedicalCenter and colleagues gathered data on 287,115 postmenopausal women who were registered in the Breast Cancer Surveillance Consortium database. Reflecting a trend in the U.S. population, 58 percent of the women in the study were overweight or obese. The women were not using postmenopausal hormone therapy when they received their mammograms between 1996 and 2005; 4,446 of them were diagnosed with breast cancer within a year of getting a mammogram.

Compared to women with a normal body mass index (BMI 18.5-24.9), risk for the first year after a mammogram was about 12 percent higher in overweight women (BMI between 25-29.9), 20 percent higher with a BMI between 30-34.9, and 30 percent higher when their BMI was higher still. Similar but independent patterns were found for high-grade, advanced-stage, estrogen receptor-positive, and large invasive disease. Factoring in the frequency of the women's previous mammogram use did not change these results.

Though under-using mammography did not entirely account for the higher rate, the authors cite its value as "the only secondary prevention measure that has been proven to decrease breast cancer mortality" by detecting disease at an earlier, more treatable stage. And though the link found here between higher BMI and advanced stage disease was moderate, it was also conclusive. "Our results suggest that postmenopausal women who are overweight or obese…should be encouraged to lose weight and to undergo routine screening mammography, two factors that may decrease the number of women who are diagnosed with advanced disease," the authors wrote.

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Part 2.

  1. If a variable is recorded in this study is the actual BMI calculated from a subject, then this BMI is what type of variable? Categorical or Quantitative?

[Type your answer here!] :

  1. If a variable is recorded based on the interval which the subject’s BMI lies, this variable takes on value 1 if a subject’s BMI in between 18.5 and 25.9, it takes on value 2 if a subject’s BMI is in between 25 and 29.9, and it takes on 3 if a subject’s BMI is 30 or above, then what type of variable is it? Categorical or Quantitative?

[Type your answer here!] :

  1. If a variable breast cancer status of a subject and it takes on only two outcomes, yes (has cancer) or no (no cancer), then what type of variable this breast cancer status variable would be? Categorical or Quantitative?

[Type your answer here!] :

  1. If one wishes to study whether BMI or Frequent Mammography affects Breast Cancer Rates, which of the three variables is(or are) the dependent variable(s) in the study?

[Type your answer here!] :

  1. If one wishes to study whether BMI or Frequent Mammography affects Breast Cancer Rates, which of the three variables is(or are) the independent variable(s) in the study?

[Type your answer here!] :

  1. Is the study experimental or observational?

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  1. What is the population of interest in this study?

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  1. What is the conclusion of this study? (Write a brief conclusion using no more than 80 words .)

[Type your answer here!]: