| The following vignette applies to the next 3 items |
It is estimated that the prevalence of smoking in a population is 50%. A cohort study conducted using a random sample from this population showed that the 5-year risk of ischemic stroke is 1:1000 among smokers and 0.5:1000 among non-smokers.
Item 1 of 3
What is the relative risk of ischemic stroke among smokers compared to non-smokers?
Relative risk (RR) represents a measure of outcome in follow-up studies. It is a risk ratio comparing risk of an outcome among the exposed to that among the unexposed. In this case, the 5-year risk of ischemic stroke among the exposed (smokers) group is 0.1% (1:1000), and the risk among the unexposed group is 0.05% (0.5:1000). As a result, the RR = 0.1/0.05 = 2.0. The 5-year risk of ischemic stroke in smokers is twice that of non-smokers.
Educational objective:
Relative risk is a measure of outcome in follow-up studies. It is the risk of the exposed group divided by the risk of the unexposed group.