HLTH 310: Fundamentals of Epidemiology
Problem Set 3: Case-Control, Cross Sectional, and Ecologic Studies
- Researchers wanted to evaluate the effectiveness of bicycle safety helmets. To do so, they conducted a case-control study with the cases being 235 people with bicycling head injuries who sought emergency care. There were 433 controls. Of the people that had a head injury, 7% were wearing helmets. And of the people that did not have an injury, 24% were wearing helmets. By what percentage was the risk of head injury reduced by wearing a helmet?
- Sixty percent of the study participants with asthma live in a smoky environment where at least one person smokes in the home and 80% of the study participants that have normal lung function do not live in a smoky environment. The prevalence of asthma in the general population is 30%. **Hint: Start with a 2×2 contingency table.
- What is the probability of asthma for people living in a smoking environment?
- What is the proportion of the total population who do not live in a smoky environment and have asthma?
- What is the prevalence of people living in a smoky environment?
- What are the odds of developing asthma when living in a smoky environment as compared to not living in a smoky environment?
- The effects of alcohol on the development of throat cancer were evaluated using a case-control study for different levels of alcohol consumption. The results are below. Using the appropriate statistical methods, determine if there appears to be a dose-response relationship between level of consumption and throat cancer. A dose-response relationship is one that shows that as the dose or exposure to a toxin increases, the response or risk of disease also increases.
| Throat Cancer | ||
| Consumption Level | Cases | Controls |
| Average (0-39 g/day) | 15 | 193 |
| Low (40-79 g/day) | 38 | 140 |
| Medium (80-119 g/day) | 26 | 46 |
| High (> 120 g/day) | 44 | 11 |
| Total | 123 | 390 |
- Between April 2015 and August 2016, there were a total of 120 cases of breast cancer in women aged 45-65 who worked at several Korean facilities that manufacture cell phones. The researchers are concerned with the effect of benzene exposure on disease rates because of the findings from 5 different studies reported below in a table. The horizontal lines represent the confidence interval for the Standardized Mortality Ratios (SMR). The dot is the SMR and the vertical line represents an SMR of 1.
Disregarding the confidence intervals, interpret the results of the table and make a statement on the effect of benzene on mortality.
Benzene is a solvent used in the final stages of cell phone production as a way to clean the components. Benzene is only used in the finishing buildings of the manufacturing facilities and workers that are in finishing, only work in the finishing area.
What type of study should the researchers conduct to see if Benzene exposure contributed to the cancer rates? Who would be included in the study and how would the researchers find the participants?
