Doctors should keep an eye on the ratio of "bad" to "good" cholesterol, rather than just the individual levels of each kind of cholesterol, to better determine their patients' risk of heart disease, according to new research.

The findings, published in the current issue of the American Journal of Preventive Medicine, may prompt refinements in guidelines for identifying and treating people with risky cholesterol levels.

The ratio of LDL (bad) to HDL (good) cholesterol and the ratio of total cholesterol to HDL cholesterol appear to be better predictors of heart disease risk than LDL levels alone, say Sundar Natarajan, M.D., M.Sc., of the New York Harbor VA and the New York University School of Medicine and colleagues.

Individuals who have similar ratios have similar risk for heart disease, regardless of any differences in their LDL or total cholesterol levels, according to the researchers. Those with higher ratios have significantly greater risk of heart disease than those with lower ratios.

Current clinical guidelines recommend using LDL cholesterol levels and other risk factors to identify high-risk people who may need cholesterol-lowering therapy. But Natarajan and colleagues suggest that LDL /HDL ratios may be better at identifying high-risk individuals and tracking their progress on cholesterol-lowering drugs.

"Despite newer recommendations incorporating HDL into risk assessment, LDL continues to be the major target of cholesterol-lowering therapy," Natarajan and colleagues say.

"However, almost half of all patients with coronary heart disease have normal LDL levels but may have low levels of HDL, resulting in a high LDL/HDL ratio," they add.

The study also has implications for the kinds of treatments recommended for patients with to high cholesterol. For instance, certain low-fat diets that reduce both LDL and HDL levels may be less beneficial than diets that boost HDL cholesterol levels. Similarly, products that are high in LDL-lowering trans-fatty acids (like margarine) may also cause an unwelcome dip in heart-protective HDL cholesterol.

Losing weight, quitting smoking and exercising can increase HDL cholesterol, and should "continue to be emphasized" for treating risky cholesterol levels, the researchers say.

The study was supported by the National Institute of Aging, the National Heart, Lung and Blood Institute, the Agency for Healthcare Research and Quality and the Department of Veterans Affairs.

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Am. J. of Preventive Medicine, Jul-2003 (Jul-2003)