Context 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.
Objective To conduct a systematic review to determine the magnitude of risk reduction
achieved by smoking cessation in patients with CHD.
Data Sources 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
Study Selection 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
Data Extraction 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.
Data Synthesis 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.
Conclusions 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.