# Risk --- **Risk** is inevatible. Everything anyone does carries a certain amount of risk, and this is true in medicine and [[nursing]]. The goal of medical treatment can thought of as performing interventions such that the potential benefit of the intervention outweighs the potential harm (i.e. risk) of the intervention. A heart transplant is potentially deadly, but so is a heart that stops working. Making these dicisions and mitigating risk is why doctors recieve such lengthy and specialized training. ## Relative Risk Frequently, the term "relative risk" is used to encompass all of these. These relative measures give an indication of the "strength of association." The relative risk (or risk ratio) is an intuitive way to compare the risks for the two groups. Simply divide the cumulative incidence in **exposed** (to a variable) group by the cumulative incidence in the **unexposed** group: So, the if a risk ratio ends up being 4.2 in this example study patients who underwent incidental appendectomy had 4.2 times the risk of post-operative wound infection compared to patients who did not undergo incidental appendectomy. It is also possible for the risk ratio to be less than 1; this would suggest that the exposure being considered is associated with a reduction in risk. The group assigned to take aspirin had an incidence of 1.26%, while the placebo (unexposed) group had an incidence of about 2.17%. The cumulative incidence in the aspirin group was divided by the cumulative incidence in the placebo group, and RR= 0.58. An appropriate interpretation of this would be: Those who take low dose aspirin regularly have _**0.58 times the risk**_ of myocardial infarction compared to those who do not take aspirin. In general: - If the risk ratio is 1 (or close to 1), it suggests no difference or little difference in risk (incidence in each group is the same). - A risk ratio > 1 suggests an increased risk of that outcome in the exposed group. - A risk ratio < 1 suggests a reduced risk in the exposed group. ___