A stroke prediction score in the elderly: validation and Web-based application

doi:10.1016/S0895-4356(01)00434-6

Journal of Clinical Epidemiology

Volume 55, Issue 2, February 2002, Pages 129-136

https://doi.org/10.1016/S0895-4356(01)00434-6 Get rights and content

Abstract

The objective of this study was to construct a prediction model for predicting stroke in an elderly U.S. population, and to assess the accuracy in this population of other previously published prediction models. The subjects were participants in the Cardiovascular Health Study: 2,495 men and 3,393 women age 65 years and older at baseline, and followed for 6.3 years. Among 5,711 participants free of baseline stroke, 399 strokes occurred. Sex-specific prediction equations were constructed using study variables that were most importantly related to incident stroke: age, systolic blood pressure, diabetes, ECG diagnosis of atrial fibrillation or left ventricular hypertrophy, confirmed history of cardiovascular disease, diabetes, time to walk 15 ft, and serum creatinine. The prediction rule was implemented as a risk score and in a Web-based interactive Java applet. Overall, the model predicted 5-year stroke risks ranging from less than 1 to 59%. The 20% of subjects in the highest predicted risk group had a 5-year actual stroke incidence rate of 15%, while the 20% lowest risk group had a 1% incidence. Risk scores from two other studies performed well in these study participants. Effective discrimination between low and high stroke risk in the elderly was possible in this cohort with data that are easy to obtain. Evaluation of the generalizability and clinical usefulness of this prediction model requires further research.

Introduction

Stroke is a major cause of mortality and disability in the United States, particularly in the elderly. A number of potent risk factors are known such as age, hypertension, and atrial fibrillation [1]. This makes it likely that stroke risk can be predicted relatively accurately. Such prediction would be of clinical and public health value, as stroke risk can be reduced in high-risk subgroups by treatment of hypertension, anticoagulation, carotid endarterectomy, or modification of other risk factors [2].

The Cardiovascular Health Study [3] (CHS) is a population-based cohort study of 5,888 men and women age 65 and older at study entry who, at the time of analysis, have been followed for a median of 6.3 years. The purpose was to investigate risk factors for cardiovascular diseases in the elderly populations. A previous article [1] reported the risk factors for stroke in this cohort. In this article we use these risk factors and those identified in other studies to construct a prediction model for stroke over a 5–7-year period in this older age group. The resulting model is presented both as a risk score calculation and as a Java applet (program that runs in a Web browser) available from the CHS World Wide Web site (http://chs3.chs.biostat.washington.edu/chs/stroke.htm). The Java applet allows risk calculations to be performed interactively using any Web browser that supports Java 1.1. Using this method, patient information can be simply entered on a computer, which applies complex statistical models that yield instantaneous calculation of a risk score.

Two stroke risk prediction models have been published: the Framingham Study model, and the Israeli Ischemic Heart Disease Project [5] (IIHD) model. The Framingham model was based on a middle to older aged population living in a single community. The IIHD model was based on an ethnically diverse, even younger population of male civil and municipal employees in Israel. To address generalizability of these scores, we applied the Framingham and IIHD models in the CHS cohort.

Section snippets

Methods

The CHS study design, including definitions of variables, has been published [3]. The cohort was recruited in two waves—the first wave of 5,201 in 1989–1990 from random samples of the Health Care Financing Administration Medicare eligibility lists in Forsyth Country, NC; Sacramento County, CA; Washington County, MD; and Allegheny County, PA. The second wave of 687 was recruited 2 years later from the same population but restricted to African-Americans to improve the representativeness of the

Results

A total of 399 strokes occurred after a median follow-up of 6.3 years, giving a rate of approximately 1.3%/year. Fifteen (3.8%) strokes were hemorrhagic and 344 (86%) were ischemic, with the remainder of unknown type. No distinction was made in the final analysis: prediction of the clinical event “stroke” was the goal of the model, the a priori most important modifiable predictor, blood pressure, is relevant to both types of stroke, and the previous models have not distinguished between stroke

Discussion

The major finding of this study was that a prediction rule could be derived to give accurate discrimination of stroke risk in this elderly population. The previously published risk models from the IIHD and Framingham studies gave comparable predictions. This indicates that the variables they incorporated capture a substantial amount of the variation in stroke risk, and suggests that the CHS model is also likely to generalize well. A simply used Java applet was presented that allows public use

Acknowledgements

The Cardiovascular Health Study is funded by the National Heart, Lung and Blood Institute through contracts N01-HC-85079 to N01-HC-85086.

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Original articleA stroke prediction score in the elderly: validation and Web-based application

Abstract

Introduction

Section snippets

Methods

Results

Discussion

Acknowledgements

Ann Epidemiol

Short-term predictors of incident stroke in older adultsthe Cardiovascular Health Study

Stroke

American Heart Association prevention conference. IV. Prevention and rehabilitation of stroke. Risk factors

Stroke

Probability of strokea risk profile from the Framingham Study

Stroke

Risk profile and prediction of long-term ischemic stroke mortalitya 21-year follow-up in the Israeli Ischemic Heart Disease (IIHD) project

Circulation

Manual of the international classification of diseases, injuries, and causes of death. Vol I. 1975 Revision

Rationale and design of a randomized clinical trial on prevention of stroke in isolated systolic hypertension

J Clin Epidemiol

Carotid artery intima and media thickness as a risk factor for myocardial infarction and stroke in older adults

N Engl J Med

Analysis of incomplete multivariate data

Survival analysis

Original article
A stroke prediction score in the elderly: validation and Web-based application