A risk factor changes probability. It does not, by itself, prove that a disease was present, prove when it began, or identify what caused it in one individual.
Medical records are full of risk factors: age, family history, tobacco exposure, body habitus, occupational loading, genetics, hypertension, diabetes, prior trauma, medication exposure, and many others. These facts can be highly relevant to causation. The problem begins when a reviewer moves from “this increases risk” to “therefore this explains the veteran’s disease” without doing the intermediate analysis.
Predisposition is not the same thing as diagnosis
A person may be predisposed to a disease for years without meeting diagnostic criteria. Family history of alcohol use disorder, for example, meaningfully increases risk, but it does not establish that the individual already had alcohol use disorder at a particular earlier date. NIAAA describes AUD as a defined medical condition and recognizes that genetics and family history contribute to vulnerability; risk and diagnosis are still different concepts.
The same principle appears throughout medicine. Obesity is a risk factor for osteoarthritis and sleep apnea. Smoking is a risk factor for multiple pulmonary and cardiovascular diseases. Age increases the probability of degenerative change. None of those facts, standing alone, answers when the disease began or why a particular patient developed it.
Diagnosis is not the same thing as causation
Even after a current diagnosis is established, the causal question remains separate. A veteran can have degenerative knee disease and multiple recognized risk factors while also having a significant service injury. The medical task is to determine how well each factor fits the pattern, timing, severity, and mechanism of the actual disease.
Three shortcuts that weaken an opinion
1. “Risk factor present, therefore cause established.” This skips the question of timing, dose, mechanism, and competing explanations.
2. “Multiple risk factors present, therefore service could not matter.” Multifactorial disease may have more than one contributing pathway. The opinion still has to explain why one pathway is medically more or less persuasive.
3. “Event happened first, therefore event caused disease.” Temporal sequence is necessary for causation but is not sufficient by itself. The mechanism and clinical course still have to fit.
Ask what the risk factor actually predicts
A stronger opinion asks several questions about each proposed risk factor:
- How strongly is the factor associated with this disease?
- Was it present before the disease began?
- Was the exposure sufficient in duration or intensity to be medically meaningful?
- Does it explain the anatomic pattern or clinical course?
- Are there objective findings that support or contradict the proposed mechanism?
- How does it compare with the competing service-related explanation?
This does not require a mathematical probability in every case. It does require more than naming the factor.
Family history deserves careful language
Family history is often particularly vulnerable to overstatement. It can identify inherited or shared environmental risk, but it generally does not tell us that the patient already had the disease, that the disease was inevitable, or that a later exposure or event had no effect. A physician should distinguish “increased baseline risk” from “documented preexisting disease.”
Aggravation questions make this even more important
When the question is whether one condition worsened another, the existence of a baseline predisposition does not end the analysis. The relevant medical issue becomes whether the later condition, treatment, altered biomechanics, or other pathway changed the severity or course beyond what would otherwise be expected. That requires a longitudinal comparison, not simply a list of risk factors.
What a better rationale sounds like
A persuasive medical rationale usually does four things: establishes the diagnosis, reconstructs the timeline, explains the plausible mechanism, and weighs alternative causes. If a risk factor is important, the opinion should say why. If it is weak, remote, or contradicted by the chronology, the opinion should say that too.
The objective is not to eliminate uncertainty. Medicine often cannot. The objective is to show how the available evidence changes the probability of the competing explanations in this particular person.
Key references
- NIAAA - Understanding Alcohol Use Disorder
- NIAAA - Genetics and Alcohol Use Disorder
- 38 C.F.R. § 3.303 - Principles relating to service connection
- 38 C.F.R. § 3.310 - Disabilities secondary to service-connected disease or injury