chicken or egg?

[Guest guest]

Greetings,

We are familiar with biomarkers that indicate disease status or direction, such

as rising LDH, IL-6, or angiogeneic growth factors .... and so on.

Similarly, TV watching habits are associated with behavior, such as the

association of watching violent TV content with aggressive social behavior.

From these associations conclusions may be formed, prematurely, that one event

causes another. That is, that watching violent TV content causes aggressive

behavior, or in research-speak: There's a causal relationship between the two

events.

In a recent NEJM article regarding the strong association between c-reactive

protein and heart disease, the author shows the possiblities in a chart,

starting with the association of the biomarker with the disease:

A) Causation: The biomarker is causally involved in the disease process

(Example1: Watching violent TV content does cause violent behavior)

(Example2: C-reactive protein causes heart disease) *

* Would be good to know because you can target the protein

with treatment to prevent or treat the disease)

OR

Reverse Causation: The biomarker is increased by the disease process.

(Example1: People predisposed to violence will also watch more violent

TV content)

(Example2: Heart disease causes elevated levels of C-reactive protein)*

* Would be good to know because you can monitor for the protein to treat

earlier or change life style to reduce risk)

OR

C) Confounding: other factors affect both the biomarker and the disease

(Example1: The TV content and aggression association was

discovered by polling unemployed people (biased study), with more

time on their hands to watch TV; having also higher stress)

(Example2: a normal genetic variation leads to increases in both heart

disease and C-reactive protein, but these are unrelated* .)

* Would be good to know because you can look elsewhere for true factors

that more

reliably predict risk and that may provide treatment targets.

I bring this up because it relates to the challenge of discovering the causal

factors for developing lymphomas, and candidate targets for treatment. Much of

research study design is an effort to create tests that prove causal

relationships, such as between therapy and outcomes. I think identifying

enviornmental factors that increase risk of lymphoma is the most challenging

research to do be cause of the sheer number of confounding variables and the

difficulty in quantifying them.

Karl