Attributable Risk Exercise
Epidemiologic research not only focuses on the identification and assessment of risk factors but also the planning and evaluating of public health interventions or control measures to reduce the incidence of disease in the population. Being able to predict the impact of removing a particular exposure on the risk of developing a disease is an important public health consideration because it allows public health planners to make decisions about allocating scarce resources (time, energy, money and political capital) for the greatest impact.
Measures of Attributable Risk answer the following questions:
What amount of the risk of developing a disease is attributable to a particular exposure?
By what percent would the risk of developing disease be reduced if the exposure were eliminated?
For public health decision-making purposes, it is valuable to be able to answer these questions from two perspectives: the impact of eliminating the exposure on only those who are exposed and impact of eliminating the exposure on the entire population.
Question 1: The preventive advantages of eating fish have been reported in numerous studies. A cohort study reported that never or rarely eating fish increased the risk for stroke. The table below shows the results of this study:
Eating Fish Stroke No Stroke
0-1 times per week 82 1,549
2+ times per week 23 779
Calculate the incidence of stroke in persons who eat fish 0-1 times per week.
Calculate the incidence of stroke in persons who eat fish 2+ times per week.
Calculate and interpret the Relative Risk for the association between eating fish and stroke.
Calculate and interpret the attributable risk among persons who never or rarely eat fish.
Calculate and interpret the attributable risk percent among persons who never or rarely eat fish.
Calculate and interpret the population attributable risk.
Calculate and interpret the population attributable risk percent.
Question 2: In a cohort study of smoking and lung cancer, the incidence of lung cancer among current smokers was 9/1,000 and 45% of the total population were current smokers. The incidence among current nonsmokers was 1/1,000.
The incidence of lung cancer attributable to smoking in the total population is:
The proportion attributable risk in the total population that is attributable to smoking is:
