Original Article
A Comparison of Risk Factors for Coronary Heart Disease and Ischaemic Stroke: The Dubbo Study of Australian Elderly

https://doi.org/10.1016/j.hlc.2009.05.001Get rights and content

Background

Conventional risk factors for coronary heart disease (CHD) and ischaemic stroke (IS) have been well documented. This study examines whether there is a unique pattern of risk factors for each disease.

Methods

This is a prospective cohort study in Dubbo NSW which has followed 2805 men and women 60 years and older for 16 years since 1988–1989. CHD and IS events were identified by hospital record linkage. The independent contributions of risk factors to these events were evaluated in proportional hazards regression models.

Results

CHD events (without stroke) occurred in 853 subjects (30.4/100). IS events (without CHD) occurred in 185 subjects (6.6/100). Some risk factors produced broadly similar prediction of CHD and IS events (male sex, current smoking, diabetes, LDL cholesterol, reduced peak expiratory flow, physical disability). Other factors potentially produced unique prediction of CHD (CHD at baseline, family history of CHD, HDL cholesterol, ApoB/ApoA1 ratio) or IS (stroke at baseline), or stronger prediction of IS compared with CHD (age, hypertension, atrial fibrillation).

Conclusions

CHD and IS may each have some unique predictors, but treatable risk factors have been demonstrated for both cardiovascular outcomes.

Introduction

It is well recognised that patients with coronary heart disease (CHD) have an increased risk of developing ischaemic stroke (IS), and vice versa, usually on the basis of atherosclerosis [1]. Underlying conventional risk factors have been well documented, such as hypertension, cigarette smoking, dyslipidaemia, diabetes and family history [1]. But the question arises – is there a unique pattern of risk factors in CHD which may differ from those in IS?

The longitudinal study of healthy ageing in 2805 senior citizens in Dubbo, NSW has separately reported risk factors for CHD (463 events over five years) [2] and IS (306 events over eight years) [3]. To our knowledge previous cohort studies have not simultaneously reported on risk factors for CHD and IS. In our earlier reports we did not exclude incident IS cases from the CHD events [2], nor did we exclude incident CHD cases from the IS events [3]. This may have led to serious confounding, especially in the stroke analyses. By the exclusion of incident IS cases from CHD events, and vice versa, we now have the opportunity to contrast the risk factors for CHD and IS in a single study over a 16-year follow-up period.

Section snippets

Participants and Baseline Examinations

The Dubbo Study cohort was first examined in 1988–1989. All non-institutionalised residents of Dubbo, NSW born before 1930 were eligible to participate. The participation rate was 73% (1233 of 1689 men and 1572 of 2171 women). Methods and measures have been described previously [4]. Briefly, the baseline examinations comprised standard demographic, psychosocial and standard cardiovascular risk assessments. The medical examination included anthropometry, blood pressure, resting ECG, peak

Results

Death occurred in 704 men (57/100 subjects) and in 683 women (43/100 subjects) during 16 years of follow-up. The following results are for men and women combined. Incident CHD events (without stroke) occurred in 853 subjects (30.4/100), while IS (without CHD) occurred in 185 subjects (6.6/100). A discrete group of 235 subjects (8.4/100) suffered both events over the passage of time.

The baseline characteristics for subjects with incident disease and in the Dubbo population free of incident CHD

Discussion

This community-based study in senior citizens 60 years and older demonstrates the genuine incidence of cardiovascular disease, based on hospitalisation or death records. As expected CHD events outnumbered IS events almost five-fold, which immediately created a problem of statistical power when comparing the outcomes. If indeed there are any important differences between CHD and IS risk factors, any confounding by subjects having both CHD and IS events would thus be more severe in the stroke

Conclusions

The present findings do have some practical implications for clinical care in senior citizens. Current smoking, diabetes, hypertension, atrial fibrillation, LDL cholesterol and low peak expiratory flow are all modifiable risk factors for cardiovascular disease. In the case of smoking, hypertension, atrial fibrillation and LDL cholesterol. We possess proof that such intervention will reduce future disease risk [9], [10], [11], [12], [13], [14]. CHD and IS may each have some unique predictors,

Acknowledgements

The authors declare no competing financial interests. This analysis did not receive any specific grant support.

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