What Really Causes Heart Attacks?

What Really Causes Heart Attacks?
Provided by: DrWeil.com

Q: I just heard about a study that found that most heart attacks are due to such factors as smoking, high cholesterol, high blood pressure and other risks we've heard about for years. What's new about this? -- Harv

A: Results of the study you're referring to were revealed at a 2004 meeting of the European Society of Cardiology and are important because they challenged medical thinking about the risk factors for heart attacks.

Until this study was reported, we believed that the risk factors you mention - smoking, high cholesterol, high blood pressure and others including diabetes, stress, abdominal obesity, a sedentary lifestyle, eating too few fruits and vegetables - accounted for about half of all heart attacks and that the other half remained to be explained.

Results from this study concluded that the risk factors contributing directly to about 90 percent of heart attacks and that therefore the vast majority of heart attacks can be prevented.

This study was unique in that it was huge - it included almost 30,000 people from 52 countries - and for the first time included a cross section of the world's population - blacks, whites, Asians, Africans, and Americans - not just white men. Half of the participants had had heart attacks and half were healthy. All were of similar age and gender and from the same region.

The researchers, from Canada's McMaster University, followed their participants for a decade and found that no matter where you live, no matter your race, sex or age, the risk factors for heart attacks are the same. Here are some of the highlights:

The higher the ratio of particles called apoproteins that carry LDL ("bad") cholesterol to apoproteins that carry HDL ("good") cholesterol, the higher your risk of heart attack.
Smoking ranked second among the risk factors. The researchers found that the risk rises with one cigarette; increases by 40 percent if you smoke one to five cigarettes a day; is four times higher than normal if you smoke a pack a day and nine times higher than normal if you smoke two or more packs a day.

Psychological stress doubled the risk of heart attack and is a greater threat when it is continuous either at home or at work. This was the most surprising finding - researchers didn't expect stress to rank as high as it did among the risk factors.

Poor intake of fruits and vegetables came next, followed by lack of exercise and sedentary lifestyle.

Drinking alcohol (in moderation) appears to lower the risk, as previous studies have also shown.
The good news here is that all of the risk factors identified can be modified by the healthy changes in lifestyle and diet long advocated for heart attack prevention. This study showed that only a small minority of heart attacks occur for unknown reasons, about 10 percent - and that by emphasizing preventive strategies we were on the right track all along. Results were published in the September 11, 2004 issue of The Lancet.

Andrew Weil, MD
Last Reviewed: April 2005