PUBH 380: Intervention Studies/Randomized Trials
Homework 4 (33 points + BONUS!)
NAME:___________________________________
Objectives
- Understand the design and analysis of cohort studies
- Define and know how to calculate and interpret risk ratios, risk differences, attributable risk percent and rate ratios
- Understand the timing of measurements, i.e. prospective, longitudinal, retrospective
- Appreciate the circumstances in which cohort studies are appropriate
Procedure
- Read the paper by Fontham et al. (1991). Lung cancer in nonsmoking women: A multicenter case-control study. Cancer Epidemiology, Biomarkers, and Prevention, 1, 35-43. You will use it to answer question 3.
For questions 1&2: based on the table and formulas below, calculate, label, AND state the meaning of your answer (interpret) in a sentence:
Status as Adolescents | Number of Participants | CHD Deaths | Person-years of observation |
Overweight | 238 | 40 | 9,329 |
Not overweight | 270 | 30 | 10,980 |
Rate Ratio = a/b
c/d
Risk Ratio = a/(a + b)
c/(c + d)
- Complete the 2×2 table based on the information above: (6 points)
Status as Adolescents | CHD Deaths | Alive | Total |
Overweight | a | b | 238 |
Not overweight | c | d | 270 |
Total | a+c | b+d | 508 |
a =
b =
c =
d =
a+c =
b+d =
- Calculate the risk of coronary heart disease (CHD) death in participants who were overweight as adolescents and in participants who were not. (8 points)
- Calculate the risk ratio of CHD death associated with having been overweight in adolescence. (4 points)
- The rate ratio of CHD death for individuals overweight at adolescence compared to lean adolescents. (BONUS 4 points)
- Based on your calculations, what can you conclude about the effect of being overweight during adolescence on the future risk of coronary heart disease? (2 point)
- Use the data on “Education” in Table 4 of the Fontham et al. (1991) article to calculate the odds ratio for the association between less than high school education vs. (some college + college + graduate education) and lung cancer in nonsmoking women. Consider “exposed” as women with less than high school education; consider “nonexposed” as the combination of women with some college, college, and graduate education. Use the population controls as the control group.
- What are the values of cells (A, B, C, and D) of the 2 by 2 table? (4 Points)
- What is the value of the odds ratio? (5 Points)
- Interpret this odds ratio in a sentence. Can this odds ratio (OR) be used as an estimate of the risk ratio (RR) (4 Points)