HLSC 148 – Epidemiology Name:_________________________________ 1. A study was conducted in a metropolitan area regarding the relationship between chili

pepper consumption and gastric cancer. The study populations consisted of 400 people with gastric cancer and 1,100 people without gastric cancer. Interviews indicated that twenty-five of the gastric cancer patients and 300 of the control group did not eat chili peppers. Based on this information, complete the table and calculate the following (include your calculations):

Gastric Cancer Controls

Ate chili peppers 375 800 Did not eat chili peppers 25 300

400 1,100

a. What type of study was conducted? Case-Control b. Calculate the proportion of exposed among the cases. a/(a+c) 375/400 = 0.938 c. Calculate the proportion of exposed among the controls. b/(b+d) 800/1,100 = 0.727 d. Calculate the odds of the diseased population having the exposure.

a/c = 375/25 = 15 e. Calculate the odds of the controls having the exposure.

b/d = 800/300 = 2.67

Based odds ratio, what conclusion can be drawn from the study? (a/c)/(b/d) or ad/bc = 5.625 – Possible high risk of developing cancer based on eating chili peppers. Can be validated with chi square.

Under what conditions would the odds ratio in this study be a reasonable approximation of the relative risk? 1. The controls are representative of the target population 2. The cases are representative of all cases 3. The frequency of disease in the population is small

2. A second study on gastric cancer and chili pepper consumption was completed in a second metropolitan area involving a defined population of 1,500 people. The study’s 2 x 2 table results were the same as in the first study.

Gastric Cancer Controls

Ate chili peppers 375 800 1,175 Did not eat chili peppers 25 300 325

a. What type of study was conducted? Cross-Sectional b. What was the prevalence of disease compared in the exposed and non-exposed

groups? a/(a+b) vs c/(c+d) 375/(375+800) vs 25/(25+300) = 0.32 vs 0.08

c. What was the prevalence of exposure compared in the diseased and non-diseased groups? a/(a+c) vs b/(b+d)

375/(400) vs 800/(800+300) = 0.94 vs 0.73