NCCMT - URE - Relative Risk it’s easy to calculate and interpret

Summary

This video explains the concept of relative risk (RR), a key tool for evaluating the effectiveness of public health interventions and understanding the relationship between risk factors and outcomes. It outlines how RR is calculated, using hypothetical examples to demonstrate its application. The script emphasizes that an RR value helps determine not only whether a relationship exists but also how strong it is. Whether studying interventions like oral hygiene education or community-based physical activity programs, RR provides valuable insights into the impact of these exposures, guiding decisions in public health practice.

Takeaways

• 😀 Relative Risk (RR) is used to assess the relationship between a risk factor or intervention and an outcome, showing not just if a relationship exists, but how strong it is.
• 😀 RR can only be calculated when there are two possible outcomes (e.g., compliance vs. non-compliance) and when one group is exposed to an intervention or risk factor, and the other is not.
• 😀 In studies where the groups are selected based on the outcome and investigated retrospectively, Odds Ratios (OR) are used instead of Relative Risk (RR).
• 😀 RR is calculated by dividing the risk of an event in the exposed group by the risk in the unexposed group. This provides a ratio that indicates the strength of the association.
• 😀 An RR of 1 means there is no difference in risk between the two groups, while an RR below 1 indicates a lower risk in the exposed group and an RR above 1 indicates a higher risk.
• 😀 For example, an RR of 0.5 means the exposed group has half the risk of the event compared to the unexposed group, representing a 50% reduction in risk.
• 😀 The further the RR is from 1, the stronger the effect of the intervention or exposure, with values approaching 0 indicating stronger protective effects and values above 1 suggesting higher risk.
• 😀 In public health, an RR below 1 typically indicates a positive outcome, such as reduced risk, but in other contexts (like promoting physical activity), an RR above 1 may represent a desired positive outcome.
• 😀 A hypothetical example shows that an RR of 1.67 means those exposed to a community-based intervention are 67% more likely to participate in physical activity compared to those not exposed.
• 😀 Understanding RR helps public health professionals assess the effectiveness of interventions and the strength of associations between risk factors and health outcomes, guiding decisions based on statistical evidence.

Q & A

What is relative risk (RR) and why is it important in public health?

Relative risk (RR) helps assess the effectiveness of an intervention or the relationship between a risk factor and an outcome. It tells us both if a relationship exists and how strong it is. It is an essential tool in evaluating public health interventions and risk factors.

What are the two necessary conditions for calculating relative risk?

Relative risk can only be calculated when there are two possible outcomes for the event being measured (such as being compliant or not compliant), and the study design follows one group exposed to a risk factor or intervention, and the other group is not exposed.

How does relative risk differ from odds ratio?

Relative risk is used when following groups forward in time and measuring the likelihood of an event occurring. In contrast, odds ratios are calculated for studies that look back in time to assess exposure among people who already have an outcome of interest.

In the example of oral hygiene education, how is the risk of dental carries calculated for the group receiving the education?

The risk of dental carries for the group receiving the education is calculated by dividing the number of children with dental carries (25) by the total number receiving the education (1,000), resulting in a risk of 0.025.

What does an RR value of 0.5 indicate in the oral hygiene example?

An RR of 0.5 means that children who received the education are at half the risk (50% lower) of developing dental carries compared to children who did not receive the education.

What would an RR of 1 indicate in terms of risk for dental carries?

An RR of 1 would mean there is no difference in the risk of dental carries between children who received education and those who did not.

If the RR was 0.25, what would that mean for the group receiving education?

An RR of 0.25 would indicate that children receiving education have a 75% lower risk of developing dental carries compared to those not receiving the education.

What is the significance of an RR above 1 in the context of a public health intervention?

An RR above 1 suggests that the intervention is associated with a higher risk for the outcome in the exposed group compared to the unexposed group. This might be desirable if the goal is to increase the occurrence of the event (e.g., promoting physical activity).

In the community-based physical activity intervention example, what does an RR of 1.67 mean?

An RR of 1.67 means that adolescents exposed to the intervention are 1.67 times more likely to engage in physical activity compared to those not exposed to the intervention.

How is the effectiveness of a community-based physical activity intervention evaluated using RR?

The effectiveness is evaluated by comparing the likelihood of participating in physical activity between those exposed (75% likelihood) and those not exposed (45% likelihood). An RR of 1.67 indicates that those exposed are 67% more likely to participate in physical activity.