Analysing the Large Decline in Coronary Heart Disease Mortality in the Icelandic Population Aged 25-74 between the Years 1981 and 2006

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Abstract

Background

Coronary heart disease (CHD) mortality rates have been decreasing in Iceland since the 1980s. We examined how much of the decrease between 1981 and 2006 could be attributed to medical and surgical treatments and how much to changes in cardiovascular risk factors.

Methodology

The previously validated IMPACT CHD mortality model was applied to the Icelandic population. The data sources were official statistics, national quality registers, published trials and meta-analyses, clinical audits and a series of national population surveys.

Principal Findings

Between 1981 and 2006, CHD mortality rates in Iceland decreased by 80% in men and women aged 25 to 74 years, which resulted in 295 fewer deaths in 2006 than if the 1981 rates had persisted. Incidence of myocardial infarction (MI) decreased by 66% and resulted in some 500 fewer incident MI cases per year, which is a major determinant of possible deaths from MI. Based on the IMPACT model approximately 73% (lower and upper bound estimates: 54%–93%) of the mortality decrease was attributable to risk factor reductions: cholesterol 32%; smoking 22%; systolic blood pressure 22%, and physical inactivity 5% with adverse trends for diabetes (−5%), and obesity (−4%). Approximately 25% (lower and upper bound estimates: 8%–40%) of the mortality decrease was attributable to treatments in individuals: secondary prevention 8%; heart failure treatments 6%; acute coronary syndrome treatments 5%; revascularisation 3%; hypertension treatments 2%, and statins 0.5%.

Conclusions

Almost three quarters of the large CHD mortality decrease in Iceland between 1981 and 2006 was attributable to reductions in major cardiovascular risk factors in the population. These findings emphasize the value of a comprehensive prevention strategy that promotes tobacco control and a healthier diet to reduce incidence of MI and highlights the potential importance of effective, evidence based medical treatments.

Related collections

Most cited references 21

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Mortality risk reduction associated with smoking cessation in patients with coronary heart disease: a systematic review.

Julia A Critchley, Simon Capewell (2003)

As more interventions become available for the treatment of coronary heart disease (CHD), policy makers and health practitioners need to understand the benefits of each intervention, to better determine where to focus resources. This is particularly true when a patient with CHD quits smoking. To conduct a systematic review to determine the magnitude of risk reduction achieved by smoking cessation in patients with CHD. Nine electronic databases were searched from start of database to April 2003, supplemented by cross-checking references, contact with experts, and with large international cohort studies (identified by the Prospective Studies Collaboration). Prospective cohort studies of patients who were diagnosed with CHD were included if they reported all-cause mortality and had at least 2 years of follow-up. Smoking status had to be measured after CHD diagnosis to ascertain quitting. Two reviewers independently assessed studies to determine eligibility, quality assessment of studies, and results, and independently carried out data extraction using a prepiloted, standardized form. From the literature search, 665 publications were screened and 20 studies were included. Results showed a 36% reduction in crude relative risk (RR) of mortality for patients with CHD who quit compared with those who continued smoking (RR, 0.64; 95% confidence interval [CI], 0.58-0.71). Results from individual studies did not vary greatly despite many differences in patient characteristics, such as age, sex, type of CHD, and the years in which studies took place. Adjusted risk estimates did not differ substantially from crude estimates. Many studies did not adequately address quality issues, such as control of confounding, and misclassification of smoking status. However, restriction to 6 higher-quality studies had little effect on the estimate (RR, 0.71; 95% CI, 0.65-0.77). Few studies included large numbers of elderly persons, women, ethnic minorities, or patients from developing countries. Quitting smoking is associated with a substantial reduction in risk of all-cause mortality among patients with CHD. This risk reduction appears to be consistent regardless of age, sex, index cardiac event, country, and year of study commencement.

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Explaining the decline in coronary heart disease mortality in England and Wales between 1981 and 2000.

Belgin Unal, Julia Alison Critchley, Simon Capewell (2004)

Coronary heart disease mortality rates have been decreasing in the United Kingdom since the 1970s. Our study aimed to examine how much of the decrease in England and Wales between 1981 and 2000 could be attributed to medical and surgical treatments and how much to changes in cardiovascular risk factors. The IMPACT mortality model was used to combine and analyze data on uptake and effectiveness of cardiological treatments and risk factor trends in England and Wales. The main data sources were published trials and meta-analyses, official statistics, clinical audits, and national surveys. Between 1981 and 2000, coronary heart disease mortality rates in England and Wales decreased by 62% in men and 45% in women 25 to 84 years old. This resulted in 68 230 fewer deaths in 2000. Some 42% of this decrease was attributed to treatments in individuals (including 11% to secondary prevention, 13% to heart failure treatments, 8% to initial treatments of acute myocardial infarction, and 3% to hypertension treatments) and 58% to population risk factor reductions (principally smoking, 48%; blood pressure, 9.5%; and cholesterol, 9.5%). Adverse trends were seen for physical activity, obesity and diabetes. More than half the coronary heart disease mortality decrease in Britain between 1981 and 2000 was attributable to reductions in major risk factors, principally smoking. This emphasizes the importance of a comprehensive strategy that promotes primary prevention, particularly for tobacco and diet, and that maximizes population coverage of effective treatments, especially for secondary prevention and heart failure. These findings may be cautiously generalizable to the United States and other developed countries.

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Explaining the decline in coronary heart disease mortality in Finland between 1982 and 1997.

Tiina Laatikainen, Julia Critchley, Erkki Vartiainen … (2005)

In Finland since the 1980s, coronary heart disease mortality has declined more than might be predicted by risk factor reductions alone. The aim of this study was to assess how much of the decline could be attributed to improved treatments and risk factor reductions. The authors used the cell-based IMPACT mortality model to synthesize effectiveness of treatments and risk factor reductions with data on treatments administered to patients and trends in cardiovascular risk factors in the population. Cardiovascular risk factors were measured in random samples of patients in 1982 (n=8,501) and 1997 (n=4,500). Mortality and treatment data were obtained from the National Causes of Death Register, Hospital Discharge Register, social insurance data, and medical records. Estimated and observed changes in coronary heart disease mortality were used as main outcome measures. Between 1982 and 1997, coronary heart disease mortality rates declined by 63%, with 373 fewer deaths in 1997 than expected from baseline mortality rates in 1982. Improved treatments explained approximately 23% of the mortality reduction, and risk factors explained some 53-72% of the reduction. These findings highlight the value of a comprehensive strategy that promotes primary prevention programs and actively supports secondary prevention. It also emphasizes the importance of maximizing population coverage of effective treatments.

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Author and article information

Contributors

: Role: Editor

Journal

Journal ID (nlm-ta): PLoS One

Journal ID (publisher-id): plos

Journal ID (pmc): plosone

Title: PLoS ONE

Publisher: Public Library of Science (San Francisco, USA )

ISSN (Electronic): 1932-6203

Publication date Collection: 2010

Publication date (Electronic): 12 November 2010

Volume: 5

Issue: 11

Electronic Location Identifier: e13957

Affiliations

[1 ]Icelandic Heart Association, Kopavogur, Iceland

[2 ]University of Iceland, Reykjavik, Iceland

[3 ]Landspitali University Hospital, Reykavik, Iceland

[4 ]Institute of Health and Society, University of Newcastle, Newcastle upon Tyne, United Kingdom

[5 ]Department of Pharmacology and Therapeutics, Trinity Centre for Health Sciences, St James's Hospital, Dublin, Ireland

[6 ]Division of Public Health, University of Liverpool, Liverpool, United Kingdom

University of Michigan, Canada

Author notes

* E-mail: v.gudnason@ 123456hjarta.is

Conceived and designed the experiments: VG GS SC. Performed the experiments: VG BT. Analyzed the data: TA VG BTM JC SC. Contributed reagents/materials/analysis tools: TA VG KA GS BT LS JC KB MO SC. Wrote the paper: TA VG BTM KA GS BT LS JC KB MO SC.

Article

Publisher ID: 10-PONE-RA-19748

DOI: 10.1371/journal.pone.0013957

PMC ID: 2980472

PubMed ID: 21103050

SO-VID: 05b0af01-6af1-4621-9f97-2f45be0e8182

Copyright © Aspelund et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

History

Date received : 8 June 2010

Date accepted : 14 October 2010

Page count

Pages: 8

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