Language
Country/Area
No result found
The secret of relative risk: How to decode risk ratios in medical research?
In today's medical research, almost every research report will mention a key indicator-relative risk (RR). This metric is critical to understanding the effectiveness of treatment and its impact on health. So, what is relative risk and how exactly does it work? This article will delve deeper into this topic and reveal the secrets behind relative risk.
The definition and significance of relative risk
Relative risk is the ratio of the probability of an outcome occurring in an exposed group to the probability of the outcome occurring in an unexposed group. This is a statistical analysis tool used in ecological, cohort, medical, and intervention studies to estimate the degree of association between exposure and outcome.
Relative risk = incidence rate of exposed group / incidence rate of unexposed group
For example, in one study looking at the effects of treatment with apixaban, 8.8% of patients in the placebo group experienced thromboembolism, compared with only 1.7% of patients treated with apixaban. group of patients developed the same disease. Therefore, the relative risk was 0.19, meaning patients taking apixaban had only 19% of the risk of disease compared to those taking placebo. This study suggests that apixaban is a protective factor rather than a risk factor in this setting.
Interpretation of relative risk
Relative risk values can provide important clinical implications:
- RR = 1: Exposure does not affect results.
- RR < 1: The exposure reduces the risk of the outcome, which is a "protective factor".
- RR > 1: The exposure increases the risk of the outcome, which is a "risk factor".
Looking back at history, however, because correlation does not imply causation, the association between exposure and outcome may be affected by other variables.
For example, the cancer risk for hospitalized patients relative to patients at home may be greater than 1, but this does not mean that hospitalization causes cancer, but rather that cancer may keep people hospitalized.
Relative risks in the report
In randomized controlled trials, relative risks are often quoted to present results. However, merely reporting relative risks without considering absolute risks or differences in risks may lead to misunderstandings. For example, when the base rate of an event is low, a larger relative risk value may not mean a significant effect, whereas when the base rate is high, a relative risk value close to 1 may still have a significant effect.
It is therefore recommended that both absolute and relative measures be reported so that the public can more clearly understand health risks.
Comparison with odds ratio
There is a difference between relative risk and odds ratio (OR). Although odds ratios approximate relative risks when the probability of the outcome is small, in practice odds ratios are often used in case-control studies because relative risks cannot be estimated.
For example, if the risk of action A is 99.9% and the risk of action B is 99.0%, the relative risk is only slightly greater than 1, but the advantage of action A is more than ten times that of action B. This difference must be handled with care when interpreting statistics.
Bayesian Interpretation
Based on Bayesian methods, we can interpret relative risk as the rate of exposure after a disease is observed. This means that relative risk takes into account not only empirical data but also changes in prior beliefs. When a disease changes the perception of risk of exposure, the relative risk value reflects this change.
Conclusion
In everyday medical research, relative risk is an important tool for assessing possible health effects, but it must be used with caution. It should be used in conjunction with other measurement tools to avoid misleading. Understanding what relative risk really means and the statistical principles behind it is critical to correctly interpreting medical research results. Have you ever changed your health decisions because of a relative risk number in a report, without knowing the specific circumstances behind it?
