# determine the association between smoking and lung cancer

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Cohort studies Practical Exercises Solutions
1. A study was carried out involving a long time follow up of 800 smokers and 1,200 non-smokers. The aim was to determine the association between smoking and lung cancer development. The table below shows the results.

Exposure
Disease Status

Totals
Lung Cancer
No Lung Cancer
Smokers
90
710
800
Non-Smokers
10
1,190
1,200
Totals
100
1,900
2000
Calculate the Relative Risk of cancer and smoking
Solutions
1. Relative Risk (RR) is incidence rates of exposed divided by the incidence rates in unexposed.
R.R. = (a/(a+b))/(c/(c+d)) = (90/800)/(10/1,200) = 13.5
Interpretation: Smokers are 13.5 times more likely to develop lung cancer than non-smokers.
2. A study was carried out to establish the association between coffee drinking and anxiety in an adult population-based sample. The total number subjects in the study were 30000 out of which 10,000 were coffee drinkers. Among the coffee drinkers, 500 developed anxiety. Out of the non-coffee drinkers, there were 200 cases of anxiety.
Estimate the relative risk of anxiety associated with coffee drinking.