A large cohort study is conducted to assess the association between smoking and squamous cell carcinoma of the esophagus among middle-aged Chinese men. During 10 years of follow-up, smokers have 5 times the risk of esophageal carcinoma compared to non-smokers (relative risk = 5.0, 95% confidence interval = 2.9-7.1). According to the study results, what percentage of squamous cell carcinoma of the esophagus in smokers can be attributed to smoking?

Question

A large cohort study is conducted to assess the association between smoking and squamous cell carcinoma of the esophagus among middle-aged Chinese men.  During 10 years of follow-up, smokers have 5 times the risk of esophageal carcinoma compared to non-smokers (relative risk = 5.0, 95% confidence interval = 2.9-7.1).  According to the study results, what percentage of squamous cell carcinoma of the esophagus in smokers can be attributed to smoking?

Quizplus · Accepted Answer

The attributable risk percent in the exposed (ARP_exposed) is an important measure of the impact of a risk factor. ARP_exposed represents the excess risk in an exposed population that can be explained by exposure to a particular risk factor. It is calculated using the following formula: This basic definition can be used to derive an equivalent formula involving relative risk (RR): Applying the formula to this example: Therefore, according to the study results, 80% of esophageal squamous cell carcinoma cases in smokers were attributable to smoking. The ARP_exposed is related to the attributable risk (AR), which is simply the difference between risk in the exposed and risk in the unexposed. Educational objective: The attributable risk percent (ARP) in the exposed represents the excess risk in the exposed population that can be attributed to the risk factor. It can be easily derived from the relative risk (RR) using the formula: ARP_exposed = 100 × [(RR - 1)/RR].

A Large Cohort Study Is Conducted to Assess the Association