BACKGROUND: The rate of adverse clinical outcomes among @entity1 with asymptomatic @entity543 receiving medical therapy alone can be used to guide clinical decision-making and to inform future research. We aimed to investigate temporal changes in the incidence rate of clinical outcomes among @entity1 with asymptomatic @entity543 receiving medical therapy alone and to explore the implications of these changes for the design of future comparative studies. SUMMARY: We searched MEDLINE, the Cochrane Central Register of Controlled Trials, US Food and Drug Administration documents, and reference lists of included studies (last search: December 31, 2012). We selected prospective cohort studies of medical therapy for asymptomatic @entity543 and we extracted information on study characteristics, risk of bias, and outcomes. We performed meta-analyses to estimate summary incidence rates, meta-regressions to assess trends over time, and simulations to explore sample size requirements for the design of future studies comparing new treatments against medical therapy. The main outcomes of interest were @entity64 , any @entity64 , @entity65 , @entity204 , and @entity583 . We identified 41 studies of medical therapy for @entity1 with asymptomatic @entity543 (last recruitment year: 1978-2009). The summary incidence rate of ipsilateral carotid @entity64 (25 studies) was 1.7 per 100 @entity1 -years. This incidence rate was significantly lower in recent studies (last recruitment year from 2000 onwards) as compared to studies that ended recruitment earlier (1.0 vs. 2.3 events per 100 @entity1 -years; p < 0.001). The incidence rates of any @entity64 (17 studies), @entity65 (6 studies), @entity204 (13 studies), and @entity583 (5 studies) were 2.7, 4.1, 4.6, and 1.8 per 100 @entity1 -years, respectively. Simulations showed that future studies would need to enroll large numbers of @entity1 with a relatively high incidence rate under medical therapy, and evaluate interventions with large effect sizes, to have adequate power to reliably detect treatment effects. KEY MESSAGES: Improved prognosis under medical therapy alone has narrowed the potential range of risk reduction attainable with new treatments for asymptomatic @entity543 . Future comparative studies will need to enroll large numbers of @entity1 to assess treatment effectiveness.

XXXX treated with medical therapy alone: temporal trends and implications for risk assessment and the design of future studies.

@entity1 :: ('9606', 'Species') :: ['patients', 'person'] @entity64 :: ('MESH:D020521', 'Disease') :: ['ipsilateral stroke', 'stroke', 'territory stroke'] @entity65 :: ('MESH:D002318', 'Disease') :: ['cardiovascular death'] @entity583 :: ('MESH:D009203', 'Disease') :: ['myocardial infarction'] @entity543 :: ('MESH:D016893', 'Disease') :: ['carotid stenosis', 'carotid artery stenosis'] @entity204 :: ('MESH:D003643', 'Disease') :: ['death']
@entity543 :: (MESH:D016893,Disease) :: ['Asymptomatic carotid artery stenosis']
