Effectiveness of low-dose ASA in prevention of secondary ischemic stroke, the ASA Study Group in Taiwan

Impacts of treatments on recurrence and 28-year survival of ischemic stroke patients

Aspirin and nicametate are well-established therapies for preventing recurrence and mortality from stroke in patients diagnosed as ischemic stroke. However, their respective effects on the recurrence, making allowance for the duration of recurrence and death without the occurrence of recurrence, and long-term survival have not been well elucidated. We aimed to evaluate long-term effect of two kinds of treatment on cerebrovascular death among ischemic stroke patients with or without the recurrence of stroke. Data used in this study were derived from the cohort based on a multicenter randomized double-blind controlled trial during 1992 to 1995 with the enrollment of a total of 466 patients with first-time non-cardioembolic ischemic stroke who were randomly allocated to receive aspirin (n = 222) or nicametate (n = 244). The trial cohort was followed up over time to ascertain the date of recurrence within trial period and death until Sep of 2019. The time-dependent Cox regression model was used to estimate the long-term effects of two treatments on death from cerebrovascular disease with and without recurrence. A total of 49 patients experienced stroke recurrence and 89 cerebrovascular deaths was confirmed. Patients treated with nicametate were more likely, but non statistically significantly, to have recurrence (aHR: 1.73, 95% CI 0.96–3.13) as compared with those treated by aspirin. Nicametate reduced the risk of cerebrovascular death about 37% (aHR: 0.63, 95% CI 0.41–0.97) compared with aspirin. The aspirin group had a lower recurrence rate than the nicametate group even with recurrence after 1–2 years of follow-up of first stroke but the latter had significantly reduced death from cerebrovascular disease for nicametate group, which requires more research to verify.

Reduction of disability after stroke is a more informative predictor of long-time survival than initial disability status

PURPOSE

Few studies have evaluated the roles of reducing disability after stroke in predicting survival. This study aimed to investigate the effects of improvement in the Barthel Index (BI) and other prognostic factors on survival in patients with first-time noncardioembolic ischemic stroke.

METHOD

BI effectiveness was defined as the improvement of BI between initial stroke (within 3 days) and 2 months after stroke. Cox regression analysis and Kaplan-Meier methods were used to evaluate the predictive roles of various prognostic factors.

RESULTS

A total of 111 patients were enrolled. Mean age at the time of stroke was 68 (+ or - 11.2) years. Median follow-up time was 77.4 months. Mean initial BI was 36.1 (+ or - 28.5) and mean BI effectiveness was 46.9 + or - 29.0. Overall, 55 deaths (49.5%) of the cohort were ascertained. The BI effectiveness had significant effects on long-time survival while initial BI was not a significant predictor. Higher BI effectiveness led to lower risk of mortality (hazard ratio = 0.44, 95% CI 0.24 - 0.80, p = 0.007). Elder age was correlated with poor survival (overall p = 0.006). Subjects in the eldest age group (> or = 70 years) showed a significant elevated risk for death (hazard ratio = 3.42, 95% CI 1.18 - 9.92). There was a trend indicating that the smaller the lesion size, the more favourable the prognosis (overall p = 0.057).

CONCLUSIONS

BI effectiveness in the first 2 months after first-time noncardioembolic stroke was more informative than initial disability status for predicting long-time mortality. It highlights the potential benefit in maximizing functional performance in patients with stroke.

Dynamic aspect of functional recovery after stroke using a multistate model

OBJECTIVE

To estimate time to functional recovery and quantify the effects of significant prognostic factors affecting the dynamic change of 3-state functional outcome after stroke.

DESIGN

Modeling of clinical predictions.

SETTING

Referral center.

PARTICIPANTS

One hundred eleven patients with first-time ischemic stroke.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Serial Barthel Index scores at onset, 2 weeks, and 1, 2, 4, and 6 months poststroke. The severity of disability was classified into 3 functional states: poor functional state (PFS) for Barthel Index scores from 0 to 40, moderate functional state (MFS) for scores from 45 to 80, and good functional state (GFS) for scores greater than 80. A 3-state Markov regression model together with Bayesian acyclic graphic underpinning was used to estimate transition parameters and mean time to functional recovery between states and to predict the probability of functional recovery by using Gibbs sampling technique.

RESULTS

The mean total recovery time was 3.1 months for patients with PFS at baseline and 1.3 months for patients with MFS at baseline. The mean recovery times to different functional states were also estimated. Age predominantly affected the probabilities of MFS to GFS transitions, younger patients had faster transition rates (rate ratio, 4.51; 95% confidence interval [CI], 2.72-7.40); but age had only borderline effects on PFS to MFS transitions. In contrast, infarct size exerted substantial effects on PFS to MFS transitions: small-size infarct correlated with a higher transition rate (rate ratio, 10.17; 95% CI, 5.25-20.13), whereas only a borderline effect on MFS to GFS transitions was found. The baseline functional state significantly affected the MFS to GFS transitions.

CONCLUSIONS

By using a multistate model, overall and patient-specific mean time to functional recovery to different functional states can be estimated and the effect of clinical predictors on functional transitions can be precisely quantified to predict patient-specific probability of functional recovery.

A Markov regression random-effects model for remission of functional disability in patients following a first stroke: a Bayesian approach

Few attempts have been made to model the dynamics of stroke-related disability. It is possible though, using panel data and multi-state Markov regression models that incorporate measured covariates and latent variables (random effects). This study aimed to model a series of functional transitions (following a first stroke) using a three-state Markov model with or without considering random effects. Several proportional hazards parameterizations were considered. A Bayesian approach that utilizes the Markov Chain Monte Carlo (MCMC) and Gibbs sampling functionality of WinBUGS (a Windows-based Bayesian software package) was developed to generate the marginal posterior distributions of the various transition parameters (e.g. the transition rates and transition probabilities). Model building and comparisons was guided by reference to the deviance information criteria (DIC). Of the four proportional hazards models considered, exponential regression was preferred because it led to the smallest deviances. Adding random effects further improved the model fit. Of the covariates considered, only age, infarct size, and baseline functional status were significant. By using our final model we were able to make individual predictions about functional recovery in stroke patients.

Location and size of infarct on functional outcome of noncardioembolic ischemic stroke

PURPOSE

Studies regarding the effects of location and size of infarct on the functional outcome after stroke have yielded inconsistent results. This study aimed to investigate the relationships of neuroimage findings and longitudinal Barthel index (BI) scores in patients with first-ever ischemic stroke.

METHOD

The neuroimage findings of enrolled subjects were grouped by anatomical location. The size of infarct was determined by the largest diameter of the lesion. Patients were followed up prospectively at onset, 2 weeks, 1, 2, 4, and 6 months after stroke. Linear mixed model was employed for the repeated measurement analysis of BI at these six time points in each patient.

RESULTS

A total of 111 patients were enrolled. The BI increased rapidly during the first two months, and reached plateau after four months. The location and size of the lesion had significant effects on serial measurements of BI. After adjustment for age, sex, treatment mode, and baseline BI score, the posterior cerebral artery infarct group showed the largest improvement in BI. There was a trend that the smaller the lesion size, the more favourable the functional outcome.

CONCLUSIONS

Both location and size of lesion in noncardioembolic stroke were significant prognostic factors for functional outcome.

Systematic review and meta-analysis of adverse events of low-dose aspirin and clopidogrel in randomized controlled trials

PURPOSE

We performed a systematic review to define the relative and absolute risk of clinically relevant adverse events with the antiplatelet agents, aspirin and clopidogrel.

MATERIALS AND METHODS

Databases were searched for randomized controlled trials of low-dose aspirin (75-325 mg/day) or clopidogrel administered for cardiovascular prophylaxis. Relative risks (RR) were determined by meta-analysis of 22 trials for aspirin versus placebo and from single studies for aspirin versus clopidogrel, aspirin versus aspirin/clopidogrel, and clopidogrel versus aspirin/clopidogrel. Absolute risk increase was calculated by multiplying RR increase by the pooled weighted incidence of the control.

RESULTS

Aspirin increased the risk of major bleeding (RR=1.71; 95% confidence interval [CI], 1.41-2.08), major gastrointestinal (GI) bleeding (RR=2.07; 95% CI, 1.61-2.66), and intracranial bleeding (RR=1.65; 95% CI, 1.06-5.99) versus placebo. No difference between 75-162.5 mg/day and >162.5-325 mg/day aspirin versus placebo was seen. The absolute annual increases attributable to aspirin were major bleeding: 0.13% (95% CI, 0.08-0.20); major GI bleeding: 0.12% (95% CI, 0.07-0.19), intracranial bleeding: 0.03% (95% CI, 0.01-0.08). No study compared clopidogrel with placebo. One study showed increased major GI bleeding (but not non-GI bleeding endpoints) with aspirin versus clopidogrel (RR=1.45; 95% CI, 1.00-2.10). The absolute annual increase was 0.12% (95% CI, 0.00-0.28).

CONCLUSIONS

Low-dose aspirin increases the risk of major bleeding by approximately 70%, but the absolute increase is modest: 769 patients (95% CI, 500-1250) need to be treated with aspirin to cause one additional major bleeding episode annually. Compared with clopidogrel, aspirin increases the risk of GI bleeding but not other bleeding; however, 883 patients (95% CI, 357-infinity) would need to be treated with clopidogrel versus aspirin to prevent one major GI bleeding episode annually at a cost of over 1 million dollars.

Comparing medications in a therapeutic area using an NNT model

OBJECTIVES

Clinicians are told to use the number needed to treat (NNT) to compare the benefits of therapeutic strategies, and researchers are asked to report results this way, generally without considering differences among the studies from which these were derived.

METHODS

The crude NNT currently advocated is compared to the NNT standardized for a common outcome, follow-up time, study population and comparator. An NNT model for cardiovascular disease is described as an example that addresses differences among studies of secondary prevention of cardiovascular disease. Crude NNTs are compared to those obtained from the model.

RESULTS

Follow-up in the 18 trials identified varied from 1.0 to 6.2 years; rates of cardiovascular events in the untreated subgroups ranged from 4.8% to 45.9%. The crude NNTs were more variable (9.1-163.7) than those obtained from the model (9.1-75.2). The effect of standardization was substantial in some cases, with proportional changes ranging from a 91% decrease to a 223% increase.

CONCLUSION

Using an NNT model to account for differences in study design allows for more meaningful comparisons.

Factors affecting the first recurrence of noncardioembolic ischemic stroke

Studies of the factors affecting the first recurrence of ischemic stroke have reported inconsistent findings. Types of initial stroke and the racial differences in study samples are among the explanations that may account for this inconsistency. The aims of this study were to estimate the cumulative recurrence rates of noncardioembolic ischemic stroke and identify the factors that influence the first recurrence of noncardioembolic ischemic stroke in the Taiwanese Chinese population. Four hundred and sixty-six patients with noncardioembolic ischemic stroke from thirteen hospitals in Taiwan were followed up in this study to ascertain first recurrence of noncardioembolic ischemic stroke between October 1992 and April 1995. The Kaplan-Meier method was used to estimate the cumulative recurrence rate. The Cox regression model was used to ascertain the significant factors affecting the first recurrence of noncardioembolic ischemic stroke. The overall cumulative recurrence rate was 10.5% (49/466) from the follow-up period of 30 months. After adjustment for age, sex, treatment modes, and variables pertinent to blood pressure, the site of brain lesion remained a significant factor. The relative risk of first recurrence for the basal ganglion vs. the region of middle cerebral artery was 3.06 (95% CI: 1.29-7.26). The brain lesion site was demonstrated to be an independent predictor of risk for the first recurrence of noncardioembolic ischemic stroke among the Taiwanese Chinese population. Whether this finding was also seen in other populations should be corroborated in future research.