EFFECT OF PERCEIVED BARRIERS ON COMPLIANCE WITH ANTIHYPERTENSIVE MEDICATION

Noncompliance with antihypertensive medication remains an obstacle to the management of hypertension, and despite research efforts over the past decade, the predictors of noncompliance remain unclear. According to values expectancy theory, individuals rationally choose noncomplia nce when the barriers or costs of treatment outweigh the expected bene fits. Noncompliance, therefore, is likely to occur when net costs of t reatment are high. Using a cross-sectional study design among subjects (n = 197) attending a specialized clinic for hypertension, we measure d ''net barriers'' (costs), self-reported compliance, and possible det erminants of noncompliance, including sociodemographics, the medical r egimen, and locus of control. The effect of each quartile of the net b arriers score (none, low, moderate, and high) on compliance, controlli ng for potential effect modifiers, was assessed using logistic regress ion modeling. Noncompliance (47%) was associated with younger age, hig her salt use, longer duration of treatment, and higher levels of net b arriers, but duration of treatment modified the effect of net barriers . Among subjects in short-term treatment, noncompliance increased with severity of net barriers suggesting a dose-response effect. In contra st, patients in long-term treatment showed no dose-response effect but a consistent association between noncompliance and levels of net barr iers. Subjects at greatest risk for noncompliance, however, were those who reported high net barriers, regardless of duration of treatment. Net barriers accounted for 50% of the noncompliance and appeared most important for patients who were younger or in the early stages of trea tment. Implications for health care providers are discussed.