Changes in Triglyceride Levels and Risk for Coronary Heart Disease in Young Men

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The summary below is from the full report titled "Changes in Triglyceride Levels and Risk for Coronary Heart Disease in Young Men." It is in the 18 September 2007 issue of Annals of Internal Medicine (volume 147, pages 377-385). The authors are A. Tirosh, A. Rudich, T. Shochat, D. Tekes-Manova, E. Israeli, Y. Henkin, I. Kochba, and I. Shai.

What is the problem and what is known about it so far?

Lipids are one of many influences that affect the risk for coronary heart disease (CHD). The 2 main forms of lipids are cholesterol and triglycerides. Both travel in the bloodstream attached to proteins called lipoproteins. Higher levels of low-density lipoprotein (called bad cholesterol) increase the risk for CHD, where higher levels of high-density lipoprotein (called good cholesterol) lower the risk. The effect of triglyceride levels on the risk for CHD is much less clear. Other well-known CHD risk factors include a sedentary lifestyle, high blood pressure, diabetes, obesity, and smoking. Some of these risk factors affect triglyceride levels, which makes it difficult to be sure whether triglyceride is a risk factor for CHD or whether it is just related to obesity, diabetes, or exercise.

Why did the researchers do this particular study?

To investigate the relationship between lipid levels in the blood and the risk for CHD.

Who was studied?

13,953 Israeli male career soldiers age 26 to 45 years. None had CHD at the beginning of the study.

How was the study done?

The soldiers had health examinations every 5 years. At each examination, the doctors obtained blood to measure lipid levels and did an exercise stress test to screen for CHD. They also asked about lifestyle factors, such as smoking and physical exercise. If the exercise test was abnormal, the doctors performed coronary arteriography to detect CHD. The researchers did statistical tests to determine whether triglycerides and changes in triglyceride levels in the 5 years between examinations were associated with newly discovered CHD.

What did the researchers find?

Triglyceride levels predicted new CHD during the 10 years after the first triglyceride level was measured. Moreover, changes in triglyceride level during the 5 years between the first and second measurements predicted new CHD in the 5 years after the second triglyceride level measurement. Men whose triglyceride levels decreased had a lower risk for CHD, and men whose triglyceride levels increased had a higher risk. Changes in triglyceride level were associated with changes in lifestyle, so that stopping smoking and increasing physical exercise were associated with lower triglyceride levels and lower risks for new CHD.

What are the limitations of the study?

The people in the study were young male soldiers. The results may not apply to other people. Although the researchers used statistical methods to even out the levels of CHD risk factors (such as cholesterol, smoking, and obesity) in groups of men with different triglyceride levels, the differences in CHD risk may have been due to risk factors that the researchers did not measure, rather than triglyceride levels. Therefore, the study cannot prove that triglyceride levels and changes in triglyceride levels cause CHD.

What are the implications of the study?

In young men, triglycerides are a risk factor for CHD. Increases or decreases in triglyceride levels are associated with increases and decreases, respectively, in CHD risk. Checking for changes in triglyceride levels might help to identify young men at extra high risk for CHD.