Prevalence of Abnormal Lipid Levels Among Youths

Prevalence of Abnormal Lipid Levels Among Youths --- United States, 1999--2006
Weekly
January 22, 2010 / 59(02);29-33


Cardiovascular disease (CVD) is the leading cause of death among adults in the United States (1). CVD risk factors, including abnormal lipid levels and elevated body mass index (BMI), often emerge during childhood and adolescence (2). In 2008, the American Academy of Pediatrics (AAP) established recommendations for targeted screening of youths aged ≥2 years for abnormal blood lipid levels (2). To provide prevalence data on abnormal lipid levels among youths, eligibility for lipid screening based on BMI, and eligibility for therapeutic lifestyle counseling among overweight youths, CDC analyzed results from the National Health and Nutrition Examination Survey (NHANES) for 1999--2006. This report describes the results of that analysis, which found that the prevalence of abnormal lipid levels among youths aged 12--19 years was 20.3%. This prevalence varied by BMI; 14.2% of normal weight youths, 22.3% of overweight and 42.9% of obese had at least one abnormal lipid level. Among all youths, 32% had a high BMI and therefore would be candidates for lipid screening under AAP recommendations. Given the high prevalence of abnormal lipid levels among youths who are overweight and obese in this study, clinicians should be aware of lipid screening guidelines, especially recommendations for screening youths who are overweight or obese.

NHANES is a continuous cross-sectional survey of the health and nutritional status of the U.S. civilian, noninstitutionalized population. Each year, approximately 6,000 persons are selected to participate in the survey through a complex, multistage probability design.* All NHANES surveys include a household interview and a detailed physical examination that includes anthropometric measurements. A randomly selected sample of NHANES participants is asked to fast for 8--24 hours. Only participants who have fasted at least 8 hours before blood specimens are taken for laboratory testing are included in the fasting sample. The results from the fasting subsample are weighted to account for the probability of selection and nonresponse.

NHANES data are released in 2-year increments; this analysis was conducted with data from the last four survey cycles: 1999--2000, 2001--2002, 2003--2004, and 2005--2006. During 1999--2006, approximately 78% of selected persons completed a physical examination component in NHANES mobile examination centers. The initial combined sample from the four surveys included 9,187 youths, aged 12--19 years, who took part in home interviews and were examined at mobile examination centers. The sample of youths who provided fasting blood samples for lipid profile testing was 3,733. From those, 73 youths who reported being pregnant or had a positive urine pregnancy test, and 535 youths for whom data were missing were excluded, for a final study sample of 3,125 youths (Table 1).

Age in years and race/ethnicity were self-reported at the time of participation. Youths were classified as non-Hispanic white, non-Hispanic black, or Hispanic. Asian youths and persons classified of other races are included in the overall analyses, but estimates for these specific groups are not reported because of small sample sizes and unstable estimates. Serum levels for youths were classified for low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides according to National Cholesterol Education Program and American Heart Association cutoff points used in the AAP screening guidelines (2) (Table 2). AAP guidelines for targeted lipid screening of youths are based on family history of high blood cholesterol, family history of premature CVD (men aged ≤55 years or women aged ≤65 years), unknown family history of high blood cholesterol or premature CVD, or the presence of at least one major CVD risk factor (smoking, hypertension, diabetes, or overweight/obesity) (2). The percentage of youths who were candidates for lipid screening in this study was determined based on BMI percentiles† (normal weight, overweight, obese). Eligibility for therapeutic lifestyle counseling among overweight and obese youths was determined based on AAP guidelines for screening and treatment (2).§ Significant differences in the prevalence of abnormal lipids as a function of demographic factors and overweight or obesity status were assessed using chi-square tests. Prevalence ratios (PRs) were used to estimate relative risk for abnormal lipids levels.

Among all youths, 20.3% had at least one abnormal lipid level based on cutoff points for high LDL-C (≥130 mg/dL), low HDL-C (≤35 mg/dL), and high triglyceride levels (≥150 mg/dL) (2) (Table 2). Compared with youths who were normal weight, overweight and obese youths were significantly more likely to have at least one abnormal lipid level (PR = 1.6 and PR = 3.0, respectively). A greater proportion of boys had low HDL-C compared with girls (11.0% versus 4.0%), and youths aged 18--19 years were more likely to have low HDL-C (10.4%) or high triglycerides (16.4%) compared with youths aged 12--13 years (4.7% and 9.5%, respectively). Youths aged 14--15 years also were more likely to have low HDL-C (8.7%) compared with youths aged 12--13 years (4.7%). High LDL-C levels differed little across age groups among the youths. The percentage of non-Hispanic white youths with low HDL-C (8.5%) or high triglycerides (12.1%) was higher compared with levels for non-Hispanic black youths (4.7% and 3.7%, respectively).

Based solely on their BMI (15% overweight youths and 17% obese youths), 32% of all youths would be candidates for lipid screening. The percentages of overweight or obese youths who were candidates for therapeutic lifestyle counseling based on lipid levels were 22.3% and 42.9%, respectively.

Reported by
AL May, PhD, EV Kuklina, MD, PhD, PW Yoon, ScD, Div for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, CDC.

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