Poorer antihypertensive adherence poses greater stroke risk
medwireNews: Researchers have established a dose-response relationship between patients’ adherence to their antihypertensive medication and their risk for stroke.
The strongest association with nonadherence was seen in the year of stroke occurrence, report Kimmo Herttua (University of Helsinki, Finland) and team. Nonetheless, nonadherence predicted stroke that occurred up to 9 years later.
The results arise from a large, population-based registry study. “Given that randomization to different adherence groups is unethical, it is unlikely that trial evidence will be available on the effect of adherence to antihypertensive medication on fatal or non-fatal stroke events,” write Herttua et al in the European Heart Journal.
Overall, nonadherence to antihypertensive medication raised the risk for fatal stroke more than threefold and for nonfatal stroke more than twofold, after accounting for variables including age, gender, diabetes, and duration of antihypertensive therapy.
The researchers’ analysis included 73,527 residents of Finland who had an ongoing antihypertensive prescription, were living in a private house, and had not previously been hospitalized for a vascular event. Of these patients, 26,704 were hospitalized with or died of stroke between January 1995 and December 2007, while 46,823 remained stroke free.
The researchers say that their results support those of previous studies, but add: “Our analysis was unique, as none of these studies assessed adherence repeatedly over time at the individual level.”
The Finnish closed pharmacy system allowed the team to assess annual medication adherence, with adherent patients defined as those who filled sufficient prescriptions to cover more than 80% of days in the year.
The influence of nonadherence on stroke risk extended back to 9 years before the event, with nonadherence 9 years previously associated with a significant 2.24-fold increased risk. But the association became stronger closer to the event, with nonadherence in the year of the stroke associated with a 5.68-fold increased risk.
Stroke risk also rose in line with decreasing adherence; for example, 30–80% adherence was associated with a 2.78-fold increased stroke risk 9 years later and a 3.60-fold increase in the same year, relative to adherence, while less than 30% adherence was associated with respective 3.97- and 7.99-fold risk increases.
“These results emphasize the importance of hypertensive patients remaining adherent to antihypertensive therapy in order to minimize such serious complications as fatal and non-fatal stroke events,” the team concludes.
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By Eleanor McDermid, Senior medwireNews Reporter