Final answer:
A lower risk ratio in epidemiology signifies a lower risk associated with exposure to a certain risk factor. The ratio compares the incidence of a health event between an exposed and a non-exposed group. Ratios less than one suggest lower risk, while those greater than one imply higher risk.
Step-by-step explanation:
In the context of epidemiology, the risk ratio is a measure used in cohort studies to compare the likelihood of a health-related event occurring between two different groups. One group is exposed to a certain variable or condition, while the other is not. A risk ratio lower than one indicates that the exposed group has a lower incidence of the health event compared to the non-exposed group, which translates to a lower risk. Vice versa, a risk ratio greater than one suggests a higher risk for the exposed group. Therefore, the lower the risk ratio is, the higher the implied protection against the health outcome or the lower the association with the risk factor.
For example, if a study shows that a population using a specific medication has a risk ratio of 0.5 for developing a certain condition, it means that this population has half the risk compared to those not using the medication. Conversely, a risk ratio of 3.25, as mentioned in an example above, would mean that the risk is over three times higher in the exposed group.