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.
1.Calculate the proper measure of association of smoking and lung cancer.
The relative risk is used to measure the association of smoking and lung cancer.
Using the Rater Ratio to estimate the RR
= 15/100000 =7.5
2/100000
Relative Risk=1
The relative risk is greater than 1 which shows an association between exposure and disease and there is an exposure between smoking and lung cancer.
2.Calculate the population risk difference.
Risk Difference = AR = I of smoker – I of non- smoker
Smoke Lung Cancer Total
Yes No
Yes
15 0 15
No 2 10,500 10,502
Total 17 10,500 10,517
AR = 15/17 – 2/10,502
AR = 0.88 – 0.19
AR = 0.69
The population risk difference is 0.69, which means that the risk of lung cancer is 0.69 times higher in smokers than in non-smokers.
Well, it seems like the smokers are in trouble. Let me do the math for you. We have 15 lung cancer deaths out of 24,500 smokers and 2 lung cancer deaths out of 10,500 non-smokers.
So, the incidence rate among smokers is 15/24,500 = 0.00061 or 0.061%.
And the incidence rate among non-smokers is 2/10,500 = 0.00019 or 0.019%.
Now, let's calculate the population risk difference. It's the incidence rate among smokers minus the incidence rate among non-smokers.
0.061% - 0.019% = 0.042% or 0.00042.
So, the population risk difference is 0.00042.
Interpreting the results, we can say that the risk of developing lung cancer is 0.042% higher in smokers compared to non-smokers. That's not a clowning matter, is it?
To calculate the population risk difference, we need to first calculate the incidence (I) of lung cancer among smokers and non-smokers.
For smokers:
Incidence (I) of lung cancer among smokers = Number of lung cancer deaths among smokers / Total number of smokers
= 15 / 24,500
= 0.000612
For non-smokers:
Incidence (I) of lung cancer among non-smokers = Number of lung cancer deaths among non-smokers / Total number of non-smokers
= 2 / 10,500
= 0.000190
Now, we can calculate the population risk difference (RD):
RD = Incidence of smokers - Incidence of non-smokers
= 0.000612 - 0.000190
= 0.000422
The population risk difference is 0.000422, which means that the risk of lung cancer is 0.0422% higher in smokers compared to non-smokers.
Interpretation: The population risk difference indicates the excess risk of lung cancer in smokers compared to non-smokers within the population. In this case, the population risk difference suggests that smokers have a higher risk of developing lung cancer, with the risk being 0.0422% higher compared to non-smokers.
To calculate the population risk difference, we need to first calculate the incidence of lung cancer among smokers and non-smokers.
Incidence (I) among smokers = Number of lung cancer deaths among smokers / Total number of smokers
= 15 / 24,500
= 0.00061
Incidence (I) among non-smokers = Number of lung cancer deaths among non-smokers / Total number of non-smokers
= 2 / 10,500
= 0.00019
Now, we can calculate the population risk difference (also known as the attributable risk):
Risk Difference (RD) = Incidence among smokers - Incidence among non-smokers
= 0.00061 - 0.00019
= 0.00042
So, the population risk difference is 0.00042.
Interpretation: This means that in this population, the incidence of lung cancer is 0.042% higher among smokers compared to non-smokers.