What is the clinical evidence from this study?

Study design: Cohort. Population: Myocardial infarction (n=7735). Intervention: Changes in cardiovascular risk factors. Primary outcome: Age-adjusted hazard of first myocardial infarction (fatal or nonfatal) (3.8% decrease per annum, 95% CI 2.6-5.0, p=<0.001).

January 23, 2008Circulation161 citations

How Much of the Recent Decline in the Incidence of Myocardial Infarction in British Men Can Be Explained by Changes in Cardiovascular Risk Factors?

Q: What are the key findings of this study?

Combined favorable changes in major cardiovascular risk factors, particularly a fall in cigarette smoking, explained 46% of the 62% decline in the incidence of first myocardial infarction over 25 years.

Q: What does this research mean for the field?

Combined favorable changes in major cardiovascular risk factors, particularly a fall in cigarette smoking, explained 46% of the 62% decline in the incidence of first myocardial infarction in British men over 25 years. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

SHSarah HardoonUniversity College Lahore PWPeter H. WhincupPreventive Cardiology LLLucy LennonUniversity College London

Key Result

Combined favorable changes in major cardiovascular risk factors, particularly a fall in cigarette smoking, explained 46% of the 62% decline in the incidence of first myocardial infarction over 25 years.

Study Design

Type

Cohort (n=7,735)

Multicenter

Yes

Structured PICO

How much of the decline in myocardial infarction incidence in British men can be explained by changes in cardiovascular risk factors?

Population

7,735 men from the British Regional Heart Study

Intervention

Changes in major cardiovascular risk factors (cigarette smoking, blood pressure, HDL and non-HDL cholesterol, body mass index, physical activity, alcohol consumption)

Outcome

Incidence of myocardial infarctionhard clinical

Population-wide improvements in cardiovascular risk factors, especially smoking and blood pressure, account for nearly half of the observed long-term decline in myocardial infarction incidence.

Main Result

Effect estimate: 3.8% decrease per annum (95% CI 2.6-5.0)

p-value: p=<0.001

Limitations

Overall statistical power and precision of the analysis were limited, resulting in wide confidence intervals
Analyses of changes in risk factors were based on attendees rather than the entire study population, potentially introducing response and survival biases
Limited data on blood pressure and cholesterol necessitated restriction of the follow-up time to the first 5 years and the last 5 years only
Effects of regression dilution were not taken into account
Analyses assumed that the effects of changes in risk factors on CHD outcomes occur within the time between consecutive questionnaires (~5 years)
Novel risk markers and diabetes mellitus were not included in the analyses

Abstract

BACKGROUND: The incidence of myocardial infarction (MI) in Britain has fallen markedly in recent years. Few studies have investigated the extent to which this decline can be explained by concurrent changes in major cardiovascular risk factors. METHODS AND RESULTS: The British Regional Heart Study examined changes in cardiovascular risk factors and MI incidence over 25 years from 1978 in a cohort of 7735 men. During this time, the age-adjusted hazard of MI decreased by 3.8% (95% confidence interval 2.6% to 5.0%) per annum, which corresponds to a 62% decline over the 25 years. At the same time, after adjustment for age, cigarette smoking prevalence, mean systolic blood pressure, and mean non-high-density lipoprotein (HDL) cholesterol decreased, whereas mean HDL cholesterol, mean body mass index, and physical activity levels rose. No significant change occurred in alcohol consumption. The fall in cigarette smoking explained the greatest part of the decline in MI incidence (23%), followed by changes in blood pressure (13%), HDL cholesterol (12%), and non-HDL cholesterol (10%). In combination, 46% (approximate 95% confidence interval 23% to 164%) of the decline in MI could be explained by these risk factor changes. Physical activity and alcohol consumption had little influence, whereas the increase in body mass index would have produced a rise in MI risk. CONCLUSIONS: Modest favorable changes in the major cardiovascular risk factors appear to have contributed to considerable reductions in MI incidence. This highlights the potential value of population-wide measures to reduce exposure to these risk factors in the prevention of coronary heart disease.

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