Progress in Chronic Disease Prevention Predicting Future Cholesterol Levels for Coronary Heart Disease Risk Assessment
Elevated total serum cholesterol level is a major risk factor for coronary heart disease (1,2). The Adult Treatment Panel of the National Cholesterol Education Program (NCEP), National Heart, Lung, and Blood Institute (NHLBI), recommends that total serum cholesterol level be measured in all adults greater than or equal to 20 years of age at least once every 5 years (3). A desirable total serum cholesterol level for adults is less than 200 mg divided by L (5.17 mmol/L). Persons with levels of 200-240 mg divided by L (5.17-6.21 mmol/L) are classified as having borderline high blood cholesterol. Persons with levels greater than 240 mg divided by L (6.21 mmol/L) are classified as having high blood cholesterol.
Recently developed statistical models (4) (based on data from the National Health and Nutrition Examination Survey 1976-1980 (NHANES II) (5,6)) describe the relationship between age and cholesterol level for men and women aged 20-57 years. The models incorporate the observed variation in the NHANES II data, the average intraperson biologic variation, and the intralaboratory variation expected when total serum cholesterol is determined. Using these models, future cholesterol levels of persons 20-57 years of age whose total serum cholesterol has been measured can be predicted. Also, based on these models, the age at which they could expect to reach borderline high or high blood cholesterol levels in the absence of a cholesterol- altering intervention can be anticipated.
Nomograms showing cholesterol projections by age have been constructed from the models (Figures 1 and 2). Based on the information in these nomograms, a 30-year-old woman with a measured total cholesterol of 155 mg divided by L (4.01 mmol/L) could expect her cholesterol level to increase to 188 mg divided by L (4.86 mmol/L) by age 50 and to reach borderline high by age 56 (curve labeled B in Figure 2). Generally, men aged 20-30 can expect an annual increase in total cholesterol of approximately 2 mg divided by L (0.05 mmol/L). From ages 30 to 60 years, the average annual increase for men declines to approximately 1 mg divided by L (0.025 mmol/L). Annual increases in cholesterol levels for women differ from those for men. For ages 20-40, the average annual increase in total cholesterol for women is approximately 1.5 mg divided by L (0.04 mmol/L); for ages 40-60, the average annual increase is approximately 2 mg divided by L (0.05 mmol/L). Reported by: Div of Environmental Health Laboratory Sciences, Center for Environmental Health and Injury Control, CDC. Editorial Note: Since serum cholesterol levels normally increase 1-2 mg divided by L (0.025-0.05 mmol/L) per year beginning in the late teens, young persons, even those with levels less than 200 mg divided by L (5.17 mmol/L), should recognize their potential for future borderline high or high classification (7-9). Use of the nomograms can aid efforts to reduce cholesterol levels in young persons (10), a population not addressed by the most recent NHLBI-NCEP recommendations (3). Through dietary and exercise intervention, teenagers and young adults can begin reducing their cholesterol before it reaches borderline high levels (11,12).
The adequacy of the constructed models was demonstrated using the individual cholesterol determinations of participants in the Framingham Study (13). The reli ability and applicability of these models for a given person will depend to a great extent on the analytical precision and accuracy of the laboratory that performed the total serum cholesterol measurement(s) (14).
Since both biologic (15) and laboratory variation (14) influence total cholesterol values, a minimum of two blood samples should be drawn and measured approximately 1 month apart (3); the average of the two results is used. If the second result differs from the first by greater than 30 mg divided by L (0.8 mmol/L), a third test should be obtained and the average of the three values used (3).
Implementation of the recent NHLBI-NCEP recommendations should lead to a reduction in coronary heart disease among adults who currently have borderline high or high cholesterol levels (16). Physicians and public health programs should be informed about the cholesterol by age projections (Figures 1 and 2). Knowledge and use of the projections could enhance the impact of these recommendations by providing an early warning to persons who could be at high risk in the future.
The reliable use of the cholesterol by age nomograms and the successful clinical application of the NHLBI-NCEP recommendations concerning critical physiologic cut-point levels for total and low-density lipoprotein cholesterol will depend on adequate standardization of the analytical measurement of lipoproteins and their constituents such as total cholesterol (14).
primary prevention trial results. I. Reduction in incidence of coronary heart disease. JAMA 1984;251:351-64.
2. Lipid Research Clinics Program. The Lipid Research Clinics primary prevention trial results. II. The relationship of reduction in incidence of coronary heart disease to cholesterol lowering. JAMA 1984;251:365-74.
3. National Heart, Lung, and Blood Institute. Report of the National Cholesterol Education Program expert panel on detection, evaluation, and treatment of high blood cholesterol in adults. Arch Intern Med 1988;148:36-69.
4. Caudill SP, Smith SJ, Cooper GR. Cholesterol-based personal risk assessment in coronary heart disease. Stat Med 1989;8:295-309.
5. NCHS, McDowell A, Engel A, Massey JT, Maurer K. Plan and operation of the Second National Health and Nutrition Examination Survey, 1976-1980. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1981; DHHS pub lication no. (PHS)81-1317. (Vital and health statistics; series 1, no. 15). 6. NCHS. Total serum cholesterol levels of adults 20-74 years of age: United States, 1976-80. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, 1986; DHHS publication no. (PHS)86-1686. (Data from the National Health Survey; series 11, no. 236).
7. Freedman DS, Shear CL, Srinivasan SR, Webber LS, Berenson GS. Tracking of serum lipids and lipoproteins in children over an 8-year period: the Bogalusa Heart Study. Prev Med 1985;14:203-16.
8. Orchard TJ, Donahue RP, Kuller LH, Hodge PN, Drash AL. Cholesterol screening in child hood: does it predict adult hypercholesterolemia? The Beaver County experience. J Pediatr 1983;103:687-91.
9. Lee J, Lauer RM, Clarke WR. Lipoproteins in the progeny of young men with coronary artery disease: children with increased risk. Pediatrics 1986;78:330-37. 10. Gillum RF, Taylor HL, Brozek J, Anderson J, Blackburn H. Blood lipids in young men followed 32 years. J Chronic Dis 1982;35:635-41. 11. Kromhout D. Body weight, diet, and serum cholesterol in 871 middle-aged men during 10 years of follow-up (the Zutphen Study). Am J Clin Nutr 1983;38:591-8. 12. Donahue RP, Orchard TJ, Kuller LH, Drash AL. Lipids and lipoproteins in a young adult population: the Beaver County Lipid Study. Am J Epidemiol 1985;122:458-67. 13. Kannel WB, Gordon T, eds. Some characteristics related to the incidence of cardiovascular disease and death: Framingham study 18-year follow-up. Bethesda, Maryland: US Department of Health, Education, and Welfare, Public Health Service, 1974; DHEW publication no. (NIH)74-599. 14. National Heart, Lung, and Blood Institute. Current status of blood cholesterol measurement in clinical laboratories in the United States: a report from the Laboratory Standardization Panel of the National Cholesterol Education Program. Clin Chem 1988;34:193-201. 15. Costongs GMPJ, Janson PCW, Bas BM. Short-term and long-term intra-individual variations and critical differences of clinical chemical laboratory parameters. J Clin Chem Clin Biochem 1985;23:7-16. 16. Lenfant C. A new challenge for America: the National Cholesterol Education Program. Circulation 1986;73:855-6.
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