Total Cholesterol Level Among US Adults Continues To Decline

21/10/05 The total cholesterol level among older adults has declined significantly, while there has been little change among younger adults, according to a study in JAMA.

Serum total and low-density lipoprotein (LDL) cholesterol contribute significantly to atherosclerosis and its related adverse effects, according to background information in the article. Previous analyses of data from the National Health and Nutrition Examination Surveys (NHANES) showed that mean (average) levels of total cholesterol of U.S. adults had declined from 1960-1962 to 1988-1994, and average levels of LDL cholesterol (available beginning in 1976) had declined between 1976-1980 and 1988-1994.

Margaret D. Carroll, M.S.P.H., of the Centers for Disease Control and Prevention, Hyattsville, Md., and colleagues evaluated trends in lipids between 1960 and 2002 and examined potential contributing factors to the trends observed. The researchers analyzed data from 5 distinct cross-sectional surveys (National Health Examination Survey [NHES] and NHANES) of the U.S. population during 1960-1962, 1971-1974, 1976-1980, 1988-1994, and 1999-2002 that included blood lipid measurements taken from 6,098 to 15,719 adults.

The researchers found: "The age-adjusted [average] total cholesterol level of adults 20 years or older decreased from 206 mg/dL (5.34 mmol/L) in 1988-1994 to 203 mg/dL (5.26 mmol/L) in 1999-2002 and the age-adjusted [average] LDL cholesterol level decreased from 129 mg/dL (3.34 mmol/L) to 123 mg/dL (3.19 mmol/L) during this same period. Significant and substantial declines in [average] total and LDL cholesterol levels were observed in men 60 years or older and women 50 years or older but not in younger adults. In general, [average] high-density lipoprotein (HDL) cholesterol levels did not change during this period. The age-adjusted geometric [average] serum triglyceride level of adults 20 years or older increased from 118 mg/dL (1.33 mmol/L) in 1988-1994 to 123 mg/dL (1.39 mmol/L) in 1999-2002 but was not statistically significant. The age-adjusted percentage of adults 20 years or older with serum total cholesterol level of at least 240 mg/dL (6.22 mmol/L or greater) decreased from 20 percent to 17 percent, thereby achieving one of the Healthy People 2010 objectives."

The authors say that a factor that likely contributed to the decrease in total and LDL cholesterol observed predominantly in the older age groups is the use of cholesterol-lowering medication. Between 1995-1996 and 2001-2002, there was an increase in the number of physician-office visits and hospital visits of men and women aged 45 years or older with statins prescribed. The researchers add that dietary data from NHANES 1999-2002 demonstrated only a small change in the overall intake of saturated fat or cholesterol.

"The continued decrease of total and LDL cholesterol levels in older adults is a positive trend. Clinical trial results suggest that a 1 percent decrease in LDL cholesterol translates into a 1 percent decrease in relative risk for coronary heart disease (CHD)," the authors write. "It appears that the decreases in total and LDL cholesterol may have been influenced more by increased medication use rather than by positive lifestyle changes. Increasing prevalence of obesity among adults may have contributed to a blunting in the decrease in total and LDL cholesterol levels, as reflected in the observed trend toward increased triglyceride levels. However, further research is needed to assess simultaneously the effects of lipid-lowering medications and other lifestyle factors on lipids."

"The National Heart, Lung, and Blood Institute's National Cholesterol Education Program recommends a healthy lifestyle, which includes reducing intake of saturated fat and cholesterol, achieving and maintaining healthy weight, and increasing physical activity for all adults, and regards additional efforts to promote such lifestyle changes to be important for achieving further improvements in the population's lipid levels. Additional analyses of these critical population lifestyle factors and lipid data are important. NHANES continues to monitor lipids and related lifestyle factors of CHD in the U.S. adult population," the authors conclude.