"I don't know" my cancer risk: Exploring deficits in cancer knowledge and information-seeking skills to explain an often-overlooked participant response

Background: Perceived risk is a central theoretical construct in health behavior research. Participants' "don't know" responses to perceived-risk items (DKPR) are usually excluded from analyses. Yet those who provide such responses may have unique cancer information needs. Objective: The hypotheses that DKPR responding may be due to cancer knowledge deficits or behavioral, skill, and attitudinal antecedents to knowledge deficits (information seeking, numeracy, and self-efficacy, respectively) were explored. Methods: Data from the 2005 Health Information National Trends Survey (HINTS; N = 1789), a US population-based survey, and an urban, minority, primary care clinic survey (N = 590) were analyzed. Multivariable logistic regressions were conducted to examine knowledge deficit explanations for responding DKPR to colon cancer risk perception questions (adjusting for demographics and family colorectal cancer history). Measures: Comparative (HINTS) and absolute verbal perceived risk of colon cancer (HINTS, clinic survey), knowledge of colon cancer risks and screening, cancer/health information-seeking behavior and self-efficacy (HINTS), and numeracy (clinic survey). Results: Greater knowledge of colon cancer prevention and screening, cancer and health information seeking, and numeracy were each associated with lower odds of providing a DKPR response. Limitations: The study was cross-sectional, which limits the ability to infer causal direction. The use of existing data sets limited our variable choices. Other plausible hypotheses may also explain DKPR responding. Conclusions: People who report that they don't know their colon cancer risk may have low cancer knowledge and reduced knowledge acquisition behaviors and skills. Health behavior research could benefit from including data concerning DKPR responses to risk perception questions, because individuals who respond in this way may require interventions to address potential cancer risk knowledge deficits.