Poor compliance with antihypertensive medications among patients with high blood pressure may greatly increase their risk of death and hospitalization due to strokes, according to a population-based study published in the July 21 issue of European Heart Journal.
A team of researchers from Finland, the U.K. and Hungary examined national prescription, hospitalization and death records of more than 75,000 patients treated for hypertension between 1995 and 2007. They assessed medication adherence annually starting at two years after it was determined that patients needed continuous treatment and up until 10 years later.
Patients were considered adherent if they had three or more purchases of antihypertensive medication during a 365-day period and there were at least 180 days between the first and last purchase.
“Hypertensive patients who subsequently died or were hospitalized due to stroke had a lower adherence to antihypertensive medication already 2 years after receiving special reimbursement for continuous antihypertensive therapy than did the patients who did not experience stroke during the follow-up,” wrote the authors, led by Kimmo Herttua, D.Soc.Sc., of the University of Helsinki.
At two and 10 years after starting continuous treatment, nonadherent patients were 3.81 and 3.01 times more likely to die from a stroke. At those same time points, noncompliant patients were 2.74 and 1.71 times as likely to be hospitalized due to a stroke.
The odds were even higher during the stroke-event year—the odds ratio for nonadherent patients was 5.68 for stroke death and 1.87 for hospitalization.
Nonadherent patients using renin-angiotensin system blockers combined with diuretics or beta-blockers were at the highest risk with odds ratios of 7.49 stroke death and 3.91 for hospitalization.
“Our findings are in agreement with previous investigations that have suggested a high adherence to antihypertensive therapy is associated with a lower risk of stroke or other cardiovascular events,” the authors wrote.
They added that unlike other studies, they assessed adherence at multiple time points.
They also noted that their research utilized a large, population-based sample as well as comprehensive national records.
However, the authors acknowledged some limitations. It is impossible to tell whether patients who had prescriptions filled actually took their medication. In addition, they did not control for several possible confounding variables, including body mass index, smoking and alcohol consumption. They may also have excluded undiagnosed hypertensives and been affected by the presence of risk factors related to nonadherence.
The team acknowledged more research is needed to better assess generalizability, but said their study drives home an important point.
“These results emphasize the importance of hypertensive patients remaining adherent to antihypertensive therapy in order to minimize such serious complications as fatal and nonfatal stroke events,” they concluded.