Healthy adherer effect - the pitfall in the interpretation of the effect of medication adherence on health outcomes
Abstract
Rationale, Aims and Objectives: Monitoring adherence to therapy is the subject of many studies. Different designs of research works may cause bias and subsequent unavailability to compare results.
Healthy adherer effect (HAE) is a type of bias reflecting patient behaviour. It cannot be easily monitored in study population and can favourably affect health outcomes that may be incorrectly attributed to drug therapy.
The aim of this article was to draw attention to HAE and characterize studies concerning the impact of HAE in relation to medication adherence and health outcomes. Methods: Review of English literature from PubMed database identified all non-experimental studies dealing with HAE.
Studies that met inclusion criteria were analysed in respect of occurrence and impact of HAE. Results: Six studies were identified - two randomized controlled and four cohort studies.
Significant occurrence of HAE in relation to mortality was not observed while one study indicated the presence of HAE in relation to surrogate (bone mineral density). Cohort studies were mainly based on drug class effect but HAE was not revealed.
Factors associated with patient behaviour (e.g. smoking, regular preventive screening) also were not clearly associated with the occurrence of HAE but their inclusion in design of cohort studies can help to detect health seeking behaviour. Conclusion: HAE was not significantly confirmed and the question of its occurrence and its impact remains open.
HAE should be assessed in other type of population, the results have to be interpreted into clinical practice carefully and be verified in further studies.