Recurrent stroke and vascular event rates have declined substantially over the last five decades, with improved blood pressure control and more frequent use of antiplatelet therapy as the leading causes, according to a meta-analysis published May 17 in Circulation.
“It is widely supposed, but not well-demonstrated, that cumulative advances in standard care have reduced recurrent stroke and cardiovascular events in secondary prevention trials,” wrote the study authors. Yet, despite advances in prevention practices, the authors pointed out that there were 15.3 million strokes and 5.7 million stroke deaths globally in 2002. Among the estimated 795,000 people with stroke in the U.S. annually, 185,000 are recurrent strokes.
Keun-Sik Hong, MD, of the department of neurology at Ilsan Paik Hospital in Goyang, South Korea, and colleagues identified all randomized, controlled trials of medical secondary stroke prevention therapies published from 1960 to 2009. They excluded randomized, controlled trials narrowly focused on single stroke mechanisms, including atrial fibrillation, cervical carotid stenosis and intracranial stenosis.
From control arms of individual trials, the researchers extracted data for baseline characteristics and annual event rates for recurrent stroke, fatal stroke and major vascular events and analyzed trends over time. They identified 59 randomized controlled trials, which enrolled 66,157 patients in control arms.
Over the five-decade period, annual event rates declined, per decade, for recurrent stroke by 0.996 percent, fatal stroke by 0.282 percent and major vascular events by 1.331 percent. Multiple regression analyses identified increasing antithrombotic use and lower blood pressures as major contributors to the decline in recurrent stroke.
For recurrent stroke, Hong et al found that the annual rates fell from 8.71 percent in trials launched in the 1960s to 6.1 percent in the 1970s, 5.41 percent in the 1980s, 4.04 percent in the 1990s and 4.98 percent in the 2000s. The sample size required for a trial to have adequate power to detect a 20 percent reduction in recurrent stroke increased 2.2-fold during this period.
“Our study suggests improvements in control of several cardinal risk factors over time. The single most important risk factor for stroke is blood pressure, which alone accounts for 30 to 40 percent of all strokes,” Hong and colleagues concluded. “The present study [however] could not directly demonstrate an increasing use of antihypertensive therapy among stroke patients because information on the rate of antihypertensive use was missing from many trial reports.”
The authors noted that “considerably larger sample sizes are now needed to demonstrate incremental improvements in medical secondary prevention,” adding that their results “can inform the design of future stroke trials.”