Keeping your "good" cholesterol (HDL) high -- with plenty of exercise and a healthy body weight -- is not only important for cardiovascular health, but could also benefit lung health, according to a new study by nutritional epidemiologists at Cornell. They find that HDL is linked to healthy lungs, though they stress that more research is needed to understand if this is a cause-and-effect relation.
"Previous studies that have looked at cholesterol and pulmonary disease reported inconsistent findings, but they all looked at total cholesterol, which may confuse the issue," said Patricia Cassano, an epidemiologist and assistant professor in the Division of Nutritional Sciences. "Our study, unlike any others we know of, examined the association of the high-density and low-density lipoproteins [HDL and LDL] with lung function."
The study is published in a recent issue of the American Journal of Epidemiology (Vol. 155, No. 9, 2002).
In an analysis of the 1988-1994 National Health and Nutritional Examination Survey of 18,162 randomly selected adults in the United States, Cassano and co-authors Dominic J. Cirillo and Yuri Agrawal, both former research assistants at Cornell, explored how HDL and LDL cholesterol are associated with lung function in healthy people. HDL and LDL, often referred to as "good" and "bad" cholesterol, have well-known and differing effects on heart disease.
Lung function was measured by a spirometer, which indicates the health of the lungs by showing the degree of airflow limitation. The measurements (including forced expiratory volume in the first second) are, said Cassano, excellent predictors of chronic obstructive pulmonary disease (COPD), the fourth leading cause of death and third leading cause of disability in the United States. Deaths from COPD, which includes emphysema and chronic bronchitis, have jumped more than 165 percent over the past three decades.
About 85 percent of people with COPD develop the disease because of cigarette smoking. However, only about 15 percent of smokers develop COPD, and researchers are interested in factors that could help to identify susceptible smokers and predict risk in nonsmokers.
Several years ago Cassano reported that antioxidants seemed to play an important role in protecting lung function and might even help prevent asthma, emphysema and chronic bronchitis (American Journal of Epidemiology Vol. 151, No. 10, 2000). Antioxidants are substances, such as beta carotene and selenium, that work in different ways to protect cells from biochemical damage. Cassano's latest study controlled for factors such as antioxidant and smoking status, alcohol intake, body fat and exercise level.
Cassano said that previous studies suggested that exceptionally low total cholesterol was linked to an increased risk of cancer, respiratory disease and other non-cardiovascular causes of death. The new study did not support these previous findings and suggested a different pattern, perhaps, in part, because it looked separately at the two sub-components of cholesterol:
Aside from potential benefits for lung health, increasing HDL levels is important for cardiovascular disease prevention. To boost HDL levels, the National Heart Lung and Blood Institute recommends maintaining a healthy weight, getting plenty of exercise and not smoking. Moderate alcohol intake also is linked to increasing HDL levels.
The study was supported in part by grants from the National Institutes of Health, the U.S. Department of Agriculture and Hatch Federal Formula Funds.
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