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Study of data from 52 countries
Smoking, High Lipid Concentration and Stress are
Main Factors Worldwide in Heart Attacks
Sept. 3, 2004 Smoking, high lipid concentrations,
and stress are the main risk factors for coronary artery disease (the
major cause of heart attack) across all world regions, according to a
study of data from 52 countries.
A secondary analysis by the same authors highlights
how stress is responsible for around a fifth of heart attacks worldwide.
Cardiovascular disease is estimated to be the
largest cause of death and disability worldwide; 80% of death and
disability occurs in low-income and middle-income countries, although
the knowledge base of the importance of risk factors is largely derived
from developed countries. This means that the effect of such factors on
the risk of coronary heart disease in most regions of the world is
unknown.
This major international study quantifying the
major risk factors for heart attack - and to identify any regional
differences from different parts of the world or among particular ethnic
groups - is detailed in the INTERHEART study, published online by THE
LANCET today.
Salim Yusuf of McMaster University, Canada, and
colleagues did a case-control study of acute myocardial infarction
(heart attack) patients in 52 countries, representing every inhabited
continent. Around 15,000 cases and 15,000 controls matched for age, sex,
and location were enrolled. The relation of smoking, history of
hypertension or diabetes, waist to hip ratio, dietary patterns, physical
activity, consumption of alcohol, blood lipids, and psychosocial factors
to heart attack were analyzed and their risk values for heart attack
calculated.
The two main risk factors identified from the study
were smoking (risk value of 2.9, ie, a nearly threefold increased risk
of heart attack for smokers compared with never smokers) and raised
lipid concentrations (risk value 3.25). Other important risk factors for
heart attack were psychosocial factors such as stress (2.7), diabetes
(2.4), family history of high blood pressure (1.9), and abdominal
obesity (1.1). Three risk factors were protective against heart attack:
the daily consumption of fruit and vegetables (0.7), regular physical
exercise (0.86), and moderate alcohol consumption (defined as moderate
alcohol intake three times a week; [0.91]). These associations were
found in men and women, old and young, and in all regions of the world.
Professor Yusuf comments: Our study has shown that
nine easily measured risk factors are associated with more than 90% of
the risk of an acute myocardial infarction in this large global
case-control study. These results are consistent across all geographic
regions and ethnic groups of the world, men and women, and young and
old. Although priorities can differ between geographic regions because
of variations in prevalence of risk factors and disease and economic
circumstances, our results suggest that approaches to prevention of
coronary artery disease can be based on similar principles throughout
the world. Therefore, modification of currently known risk factors has
the potential to prevent most premature cases of myocardial infarction
worldwide.
The same investigators did a more detailed analysis
of the psychosocial factors associated with increased heart-attack risk.
Around 11,000 of the 15,000 cases from the main study and 13,600
controls were assessed. Psychosocial stress was assessed by four simple
questions about stress at work and at home, financial stress, and major
life events in the past year. Cases reported higher prevalence of all
four stress factors: of those cases still working, 23% experienced
several periods of work stress compared with 18% of controls; 10%
experienced permanent work stress during the previous year compared with
5% of controls. Around 12% of cases had several periods of stress at
home compared with around 9% of controls; financial problems were a
major contributor to stress at home. Overall, the relationship between
stress and increased risk of heart attack was consistent across all
world regions and ethnic groups studied, contributing to over a fifth
(22%) of all heart attacks worldwide.
In an accompanying commentary, Majid Ezzati of the
Harvard School of Public Health, states that INTERHEART provides further
confirmation that for many common cardiovascular risk factors,
differences in total risk across populations are more a result of
variations in exposure and background levels of disease than an outcome
of different causal processes. For these risks, Ezzati says: In
parallel to advancing our basic understanding of causative mechanisms,
we can safely begin to pay attention to design of effective
interventions, and more importantly to programs for delivery of
available interventions to those at need.
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