Introduction

We've talked about the risk factors for coronary heart disease (CHD) often in the past, citing studies that show that they are closely associated with a cardiovascular 'event', such as a heart attack (myocardial infarction, or MI), angina, stroke, or sudden cardiac death. The problem in trying to hammer home the importance of tackling risk factors has been that, until now, popular medical wisdom has stated that "half the people who have an MI don't have a single cardiovascular risk factor". That has changed, as a study in the Journal of the American Medical Association shows.

What was done

Chicago physicians analyzed three large studies in which participants were followed for 21 to 30 years. The studies were: the Chicago Heart Association Detection Project in Industry (CHA), the Multiple Risk Intervention Trial (MRFIT), and the Framingham Heart Study (FHS). They measured the occurrence of major risk factors and of fatal CHD events; non-fatal heart attacks were also measured in the FHS. The risk factors studied were defined as follows:

• Total cholesterol of at least 240 mg/dL (6.33 mmol/L)
• Diastolic blood pressure of at least 90 mm Hg or systolic at least 140 mm Hg
• Current medication with cholesterol- or blood pressure- lowering drugs
• Current cigarette smoking
• A clinical diagnosis of diabetes

For this analysis, CHD events were defined as death due to CHD, or a non-fatal heart attack. The men and women participants were analyzed separately, using two age groupings: 18-39, and 40-59 years.

What was found

There were 387,000 participants in the 3 studies combined. A total of 20,000 fatal CHD events occurred, and there were 305 non-fatal heart attacks in the FHS.

The percentage of men and women of different ages who died from CHD, and who had at least one CHD risk factor, are given in the table:

	Men		Women
Study	18-39 years	40-59 years	18-39 years	40-59 years
CHA	95%	93%	92%	94%
MRFIT	88%	87%	(no women included)
FHS	90%	90%	100%	90%

For non-fatal heart attacks, measured in the FHS, percentages ranged from 69% in the younger women to 92% in the older men.

Further analyses were done using lower levels of risk (but still values above normal) - cholesterol over 200 mg/dL (5.2 mmol/L), blood pressure above 120/80 mm Hg, smoking, and presence of diabetes. Percentages of those dying from CHD who had at least one of these lesser levels of risk ranged from 96% to 100%.

What this means

This analysis shows that a very high proportion of those who experience a CHD event (death, or a non-fatal heart attack) have at least one major risk factor for CHD. Instead of half, as many as 9 out of 10 people with a heart attack have a major risk factor - raised cholesterol, raised blood pressure, smoking, or diabetes.

The results were similar in three independent studies. And in another publication in the same Journal, doctors from the Cleveland Clinic come to the same conclusions, based on analysis of records from over 120,000 patients.¹ They found that 80% to 90% of patients with CHD had one or more risk factors.

Are there other relevant risk factors for CHD? A review of these in the same issue of the Journal comes to the conclusion that C-reactive protein (CRP), lipoprotein(a), fibrinogen, and homocysteine are all associated with increased risk; however, the evidence is not so clear, to date, and their use in routine screening should probably be delayed until further studies have been done.²

The conclusions to be drawn are obvious. The repeated warnings about risk factors for heart disease are to be taken seriously, and acted upon. This means lifestyle changes: stop smoking, start exercising and eat right; the idea is to get your lipid profile under control, keep your blood pressure below 120/80, and manage your diabetes, if you have it. And, take the medication(s) your doctor may prescribe to help you in your efforts.