In a population-based cohort study, an entire community was interviewed regarding smoking habits and then followed for one year. All lung cancer deaths were ascertained and the following data were available:
Fifteen (15) lung cancer deaths occurred among 24,500 smokers
Two (2) lung cancer deaths occurred among 10,500 non-smokers
Calculate the following and interpret your results in each case.
Calculate the proper measure of association of smoking and lung cancer.
Calculate the population risk difference.
Calculate the population attributable risk for smoking and lung cancer
To calculate the proper measure of association of smoking and lung cancer in this population-based cohort study, we can use the relative risk (RR). The relative risk compares the risk of developing a disease or outcome between two groups. In this case, we will compare the risk of lung cancer between smokers and non-smokers.
First, we need to calculate the incidence of lung cancer in each group:
For smokers:
Incidence of lung cancer = Number of lung cancer deaths among smokers / Total number of smokers
Incidence of lung cancer = 15 / 24,500 = 0.00061
For non-smokers:
Incidence of lung cancer = Number of lung cancer deaths among non-smokers / Total number of non-smokers
Incidence of lung cancer = 2 / 10,500 = 0.00019
Now, we can calculate the relative risk:
Relative Risk (RR) = Incidence of lung cancer in smokers / Incidence of lung cancer in non-smokers
RR = 0.00061 / 0.00019 = 3.21
Interpretation: The relative risk of developing lung cancer among smokers compared to non-smokers in this study is 3.21. This suggests that smokers have a 3.21 times higher risk of developing lung cancer compared to non-smokers.
Next, let's calculate the population risk difference. The risk difference measures the absolute difference in the risk of an outcome between two groups.
Population Risk Difference = Incidence of lung cancer in smokers - Incidence of lung cancer in non-smokers
Population Risk Difference = 0.00061 - 0.00019 = 0.00042
Interpretation: The population risk difference for smoking and lung cancer in this study is 0.00042. This means that out of every 10,000 individuals, 4.2 additional cases of lung cancer would occur among smokers compared to non-smokers.
Lastly, let's calculate the population attributable risk for smoking and lung cancer. The population attributable risk quantifies the proportion of the disease burden in the population that is attributable to a particular risk factor.
Population Attributable Risk (PAR) = (Incidence of lung cancer in smokers - Incidence of lung cancer in non-smokers) / Incidence of lung cancer in smokers
PAR = 0.00042 / 0.00061 = 0.6885
Interpretation: The population attributable risk for smoking and lung cancer in this study is 0.6885. This means that approximately 69% of the cases of lung cancer in the population can be attributed to smoking.
Please note that the results and interpretation provided are based on the information given in the question. It's important to consider the limitations of the study and any potential confounding factors.