Poor Adherence to Blood Pressure Rx Ups Risk of Stroke

New research reported on July 16 by the European Heart Journal online found that patients with hypertension who do not adhere to prescribed antihypertensive regimens are at greatly increased risk for stroke, hospitalization for stroke, and stroke-related mortality.

The findings may seem an obvious outcome of nonadherence with a course of therapy, but the authors note this is the first study to follow patients over an extended period with regular assessment of how closely they were adhering to a physician’s prescription and how that measure correlated with fatal and non-fatal stroke.

The study, conducted by Herttua and colleagues in Finland, evaluated Finnish national registries that cover prescriptions, hospitalizations, and deaths spanning the years 1995 to 2007. Analysis included 73,527 patients aged 30 years and older who required continuous antihypertensive therapy for a diagnosis of hypertension and who had no history of stroke or cardiovascular disease at baseline.

Nonadherent patients were more likely than those who consistently took their antihypertensive medications to die of stroke at 2 years (OR = 3.81; 95% CI, 2.85-5.10), 5 years (OR = 3.68; 95% CI, 2.92-4.65), and 10 years (OR = 3.01; 95% CI, 2.37-3.83) after starting continuous treatment. 

The corresponding odds ratios for stroke hospitalization were 2.74 (95% CI, 2.35-3.20), 2.28 (95% CI, 2.00-2.60), and 1.71 (95% CI, 1.49-1.96). 

There was a clear dose-response relationship between the degree of nonadherence and level of risk for poor outcome when researchers compared patients who took medications appropriately as prescribed more than 80% of the time with those with intermediate (30% to 80%) and poor adherence (<30%). In the year that a fatal or nonfatal stroke occurred, patients in the intermediate and poor adherence groups had a 1.7-fold and 2.6-fold higher risk of nonfatal stroke and 3.6-fold and 8-fold higher risk of fatal stroke, respectively, compared with patients with good adherence.

When study authors assessed stroke risk based on adherence to specific classes of antihyhpertensive medication, they found that for agents that act on the renin-angiotensin system combined with diuretics or beta-blockers, nonadherence was associated with a 7.5-fold higher risk (OR = 7.49; 95% CI, 5.62-9.98) and a nearly 4-fold higher risk (OR = 3.91; 95% CI, 3.23-4.75) for mortality, respectively, in the year that these events occurred vs adherence to these medications.

Antihypertensive drug therapy remains a primary stroke-prevention strategy in affected patients. The study reinforces for primary care physicians the importance of patient education and other supportive interventions to ensure the greatest possible level of adherence to prescribed regimens.

Source:
Herttua K, Tabk AG, Martikainen P, et al. Adherence to antihypertensive therapy prior to the first presentation of stroke in hypertensive adults: population-based study. Eur Heart J. 2013; doi:10.1093/eurheartj/eht219.