Intentional and unintentional nonadherence to antihypertensive medication.

BACKGROUND: Hypertension is poorly controlled in the US due to medication nonadherence. Recent evidence suggests that nonadherence can be classified as intentional or unintentional and different patient characteristics, such as the experience of adverse effects, may be associated with each.

OBJECTIVE: To examine associations between patient characteristics, including reported adverse effects, and both intentional and unintentional nonadherence among 588 hypertensive patients.

METHODS: Baseline data from a clinical trial, the Veterans' Study To Improve the Control of Hypertension, were examined. Intentional and unintentional nonadherence were assessed using a self-report measure. Participants were presented with a list of adverse effects commonly associated with antihypertensive medication and asked to indicate which symptoms they had experienced. Logistic regression analyses were used to examine adjusted associations between patient characteristics and type of nonadherence.

RESULTS: Approximately 31% of patients reported unintentional nonadherence and 9% reported intentional nonadherence. Non-white participants, individuals without diabetes mellitus, and individuals reporting > or = 5 adverse effects were more likely to report intentional nonadherence than their counterparts. Individuals with less than a 10th-grade education and non-white participants were more likely to report unintentional nonadherence than their counterparts. When symptoms of increased urination and wheezing/shortness of breath were reported, patients were more likely to report intentional and unintentional nonadherence compared with those who were adherent. Unintentional nonadherence was also associated with reports of dizziness and rapid pulse.

CONCLUSIONS: Both intentional and unintentional nonadherence are common and related to perceived adverse effects. Furthermore, different interventions may be necessary to improve adherence in unintentionally and intentionally nonadherent patients.