What is a risk factor?

• A. A determinant that could increase the risk of a given disease/infection
• B. A protective factor that reduces risk
• C. A measure of disease prevalence
• D. A statistical method for testing associations

Answer: (A)

A risk factor is any characteristic or exposure that increases the probability of developing a disease. It can be a behavior, environmental exposure, genetic trait, or health condition that is associated with a higher likelihood of illness. For example, smoking is a risk factor for lung cancer because people who smoke have a higher chance of developing it compared with non-smokers. Note that a risk factor does not guarantee disease, and not all risk factors are proven to be causal—some associations may be due to confounding or other biases.

The other ideas aren’t risk factors: a protective factor reduces risk rather than increases it; a measure of disease prevalence describes how common the disease is in a population, not something that influences risk; and a statistical method for testing associations is about analysis, not a factor that alters disease risk.