What is the Origin of Healthy User Effect?

This term originated in the field of epidemiology to acknowledge and address a common methodological challenge in non-randomized studies. It recognizes the self-selection phenomenon in health research, where adherence to medical advice is a marker of a broader commitment to wellness. The concept gained particular relevance in the analysis of long-term hormone therapy trials where participants with better overall health were more likely to continue treatment.

What is the Mechanism of Healthy User Effect?

The mechanism is one of statistical confounding: the healthier lifestyle factors—such as regular exercise, better diet, and non-smoking status—are associated with both the decision to use the therapy and the improved health outcomes. Unless these confounding variables are meticulously measured and statistically adjusted for, the study risks falsely attributing the health benefits to the therapy when they actually stem from the user's pre-existing healthy behavior pattern.

Healthy User Effect

Meaning

The Healthy User Effect is a pervasive form of confounding bias encountered in observational epidemiological studies, particularly those assessing the benefits of medications or health interventions. This bias occurs because individuals who choose to take a prescribed medication or adopt a specific health behavior, such as hormone therapy, often possess inherently healthier baseline characteristics and lifestyle factors than those who do not. Consequently, the observed positive outcomes may be partially or wholly attributable to these unmeasured healthy habits rather than the intervention itself.