What is Biological Plausibility?
Biological plausibility refers to the extent to which a causal association between an exposure and a health outcome is consistent with existing biological and medical knowledge. It is an important criterion in epidemiology that helps to establish whether an observed relationship is likely to be causal. This concept is often assessed by examining the mechanisms through which an exposure might lead to an outcome, supported by laboratory research, clinical studies, and an understanding of biological processes.
Why is Biological Plausibility Important?
Biological plausibility is crucial because it adds a layer of credibility to epidemiological findings. While statistical associations can suggest a link between an exposure and an outcome, they do not prove causation. Plausibility provides a biological rationale that supports or refutes these findings. Without it, associations might be dismissed as spurious, even if they are statistically significant.
Review of Existing Literature: Examining prior research on the exposure and outcome can reveal established biological mechanisms that support the association.
Laboratory Experiments: Laboratory studies can provide evidence of biological mechanisms. For example, animal models or cellular studies can show how a substance affects biological systems.
Clinical Studies: Observational and interventional studies in humans can offer insights into how an exposure might lead to a health outcome.
Examples of Biological Plausibility
Consider the relationship between smoking and lung cancer. The biological plausibility of this association is supported by the fact that tobacco smoke contains carcinogens that can damage DNA and lead to cancer. Similarly, the link between
high cholesterol levels and
heart disease is biologically plausible because cholesterol can contribute to the formation of atherosclerotic plaques, which in turn can lead to cardiovascular events.
Challenges in Establishing Biological Plausibility
There are several challenges in establishing biological plausibility: Complexity of Biological Systems: Human biology is complex, and multiple pathways can lead to the same outcome. This makes it difficult to pinpoint a single mechanism.
Variability Among Individuals: Genetic and environmental factors can cause variations in how individuals respond to the same exposure.
Incomplete Knowledge: Our understanding of biological processes is constantly evolving, and current knowledge may be incomplete or incorrect.
Biological Plausibility and Epidemiological Criteria
Biological plausibility is one of several criteria used to assess causality in epidemiology, often referenced in the context of
Bradford Hill criteria for causation. Other criteria include strength of association, consistency, specificty, temporality, dose-response relationship, and coherence. While biological plausibility alone cannot prove causation, it strengthens the overall argument when combined with these other factors.
Conclusion
In summary, biological plausibility plays a vital role in epidemiology by providing a scientific basis for causal inferences. It integrates knowledge from various scientific disciplines to support or refute epidemiological findings. Despite its challenges, it remains an indispensable tool for understanding the complex relationships between exposures and health outcomes.
